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Imbrium Lunokhod Industries Model VS-MU-333 'Lorikeet' is the next step in Imbrium Lunokhod Industries Frame System. This mass produced frame builds on the versatile and flexible mobile frame platform made popular by the VS-M/S-71 'Degei' (flic.kr/s/aHsm37uTTm) and the VS-MX-04 'Rangi' (flic.kr/s/aHsk4AUkEY). Developed for planetary surface operations and utility deployments, the Lorikeet will definitely not excel in zero-g environments, it's outclassed by more maneuverable specialty frames. But for deployments to planetary surfaces, the frame offers a more affordable (although less durable) alternative to the Varuna (flic.kr/s/aHsm89p5MW) the a more extensible (and repairable) alternative to the Krivlyaka (flic.kr/s/aHsm4d6e2v).
From a design perspective, the frame takes a ton of inspiration from both Malcolm Craig's MgN-333 (flic.kr/p/dEFocc) and Aardvark17's Budgie (flic.kr/p/2kgyyua) frames as well as my version of the HR-13 flic.kr/s/aHsmMLcB3m.
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Built for Mobile Frame Zero - a tabletop wargame.
Mobile Frame Hangar Nova (MFZ Community Forums).
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Look what I found in the archives last night - I think we're looking right down its air tube, here, and it appears to be working on its cover. This is a follow-up to yesterday's post, which made some of us curious about how spittlebug nymphs breathe under all that foam.
"The nymphs breathe and form bubbles in the spittle fluid by means of a ventral air tube formed by overlapping abdominal plates (Kershaw 1914). The tip of this extensible tube periodically pokes through the surface of the spittle mass and conveys air to abdominal spiracles, permitting spittlebug nymphs to breathe in a manner analogous to mosquito and syrphid fly larvae (Ward 1991, Wlliams & Feltmate 1992)." - Vinton Thompson in this PDF file.
Spittlebug nymph in spittle
C&O National Historic Park, Great Falls, MD
The hatch folds up nice enough, but the compact space is making an extensible ladder/staircase a challenge.
Coucou! Here I am. Halloweenface.
Commerson's frogfish grows up to 38 cm (15 in). Like other members of its family, it has a globular, extensible body. The soft skin is covered with small dermal spinules. Its skin is partially covered with a few small, wartlike protuberances, some variably shaped, scab-like blotches, and a few, small eye spots (ocelli) reminiscent of the holes in sponges. Its large mouth is prognathous, allowing it to consume prey as large as itself. Their coloration is extremely variable, as they tend to match their environments. Frogfish can change their coloration in a few weeks. However, the dominant coloration goes from grey to black, passing through a whole range of related hues, such as cream, pink, yellow, red, and brown, and also usually with circular eye spots or blotches that are darker than the background.
Nuweiba, Gulf of Aqaba, Egypt
Torrelavega-Azuqueca, de Transfesa Rail, con la 335.019. Todo ello salvo error u omisión.
Ávila, 8 abril 2014; 17.15 h. Y detrás preparándose el portacamiones de Nissan Ávila-Can Tunis, que partió más tarde.
Saludos al maqui, extensible.
La Kodak Medalist I és una càmera impressionant. Pesada, ferma i (aquesta sí) construida com un tanc, també compta amb una magnífica optica i acabats. Probablement és la càmera de més qualitat que mai va sortir de Kodak a Rochester. Tant per estètica (obra del famós Walter Teague) com per construcció, sembla l'equivalent fotografic els grans Chevrolet o GMC dels anys 40.
Tot i que el diseny original és civil, del 1941, l'inici de la Segona Guerra Mundial feu que les seves caracteristiques (robustessa + gran qualitat de fotografía) fossin ideals per als militars americans, en especial la US Navy. Per tant és pràcticament la única camera que es produí durant la guerra, anant en principi tota la producció a les forces armades. Després de la guerra es fabricà la Medalist II, molt similar i ja per a el mercat civil de post-guerra. El gran objectiu extensible inicialment era metalitzat, però ràpidament passà a un acabat anoditzat negre per resistir l'ambient marí de la flota. L'objectiu és un Kodak Ektar f3,5 100mm en un obturador Kodak Supermatic No.2. Per tant tota la càmera és completament americana i Kodak. Fins hi tot una placa a la part posterior remarca que és "Made in the United States of America", quant totes les càmeres de gran qualitat el mercat (Leica, Contax....) eren alemanes, es a dir, del enemic.
Aquest exemplar sembla produit el 1944, per el nº de serie del objectiu, EE (es a dir 44 segons el codi Kodak).
====================
The Kodak Medalist I is an impressive camera. Heavy, solid, and built like a Sherman tank, also has a magnificent optics and rangefinder. It is probably the highest quality camera that never came out of Kodak at Rochester. Both for aesthetics (the work of the famous Walter D. Teague) and construction, it looks like the photographic equivalent of the great Chevrolet or GMC's of the 40s.
Although the original design was made for the civilan market in 1941, the beginning of World War II made its features (robustness + high quality photography) ideal for the American military, especially the US Navy. Therefore it is practically the only camera that continued production during the war, going probably all the stock to the armed forces. After the war the Medalist II, very similar but oriented to the post-war civillian market, was made. The large extensible lens was originally metallized, but quickly changed to an anodized black finish to resist the marine environment in the Navy. The lens itself is a Kodak Ektar f3.5 100mm in a Kodak Supermatic No.2 leaf shutter. Therefore, the whole camera is completely American and Kodak. Even a plaque on the back emphasizes that it is "Made in the United States of America," when all the high quality cameras (Leica, Contax ....) were of German origin, that is, the enemy.
This one appears to have been produced in 1944, for the serial number of the target, EE (ie 44 according to the Kodak code). It uses 620 roll film, which could be made respooling 120 film into 620 spools.
camera-wiki.org/wiki/Kodak_Medalist
www.filmshooterscollective.com/analog-film-photography-bl...
photojottings.com/kodak-medalist-and-fuji-gw690iii-compar...
IN ENGLISH BELOW THE LINE
La Gundlach Korona View és una càmera nord-americana de gran format, força lleugera i de gran qualitat. Com podeu veure, és de triple (suposo) expansió. És a dir, que la manxa pot expandir-se el triple de la distancia d'enfoc a infinit, permetent enfocar molt a prop, o amb focals molt llargues. Per això compta amb una base extra desmontable.
Aquesta càmera en concret és la Korona View de segón model, fabricada entre 1909 i els anys 30; en tot cas aquesta data d'abans del 1926, ja que la companyia canvià de nom. És de format 5x7 polzades i la vaig comprar amb un objectiu Plaubel Anticomar f4.2 / 210mm montat en un gran obturador Compound; junt amb la càmera anaven tres portaplaques dobles amb el nom del antic propietari, Dr. H. B. Wright. Tot plegat sembla indicar que fou venguda als Estats Units als anys 20 o 30.
És molt curiós perquè la vaig comprar amb la idea exprés de fer-la servir per a fer plaques de col·lodió, i un dels tres portaplaques estava precisament adaptat per a col·lodió (i marcat com a tal).
Per cert, només em vaig adonar a posteriori que havia comprat una càmera que porta per nom KORONA just aquest any 2020.
www.piercevaubel.com/cam/gundlach/view.htm
camera-wiki.org/wiki/Korona_View_Camera
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The Gundlach Korona View is a large format American camera, quite light and built in high quality materials. As you could see, it's a triple expansion camera. This means that the bellows can be extended three times it's infinte focus distance. This enables the camera to focus much closer, or to mount longer focal lenses. An extra base is mounted at the back of the camera, as here demonstrated.
This particular item is the 2nd. model Korona View, made between 1909 and the 1930s; but this one was made before changing the name of the company in 1926. It is a 5x7 format camera and I bought it with a Plaubel Anticomar f4.2 / 210mm lens mounted on a large Compound shutter; along with the camera were three double plate holders with the name of the former owner, Dr. H. B. Wright. All this seems to indicate that it was sold in the United States in the early 1920's.
It’s very curious because I bought it with the express idea of using it to make collodion wet plates, and one of the three plate holders was precisely adapted for collodion (and marked as such).
By the way, have you noted that I bought a camera named Korona pricely in this 2020? The year of what...?
www.piercevaubel.com/cam/gundlach/view.htm
camera-wiki.org/wiki/Korona_View_Camera
www.historiccamera.com/cgi-bin/librarium2/pm.cgi?action=a...
IN ENGLISH BELOW THE LINE
La Plaubel Makina II és una càmara de gran format de meitat del s. XX, extensible i destinada sobretot a la premsa. Feia servir plaques de 6,5x9cm però s'adapta sense problemes a porta-rodets de format 120, com en el cas d'aquesta.
Es tracta d'un ambrotip amb vidre fosc, de format 4x5 polzades, realitzat amb una Graflex Pacemaker Speed Graphic fabricada cap al 1949; objectiu Kodak Anastigmat f4.5. Col·lodió Old Workhorse de Franalog.
Les plaques de col·lodió es realitzen al moment, cobrint una placa de vidre o planxa metal·lica negra amb col·lodió i sals de cadmi i/o potassi, sensibilitzat amb nitrat de plata. Aleshores s'ha de fer la fotografia i revelar-la en uns 5 minuts, abans no s'assequi la emulsió. És un dels processos fotogràfics més antics del món, inventat el 1851, i que dominà fins el 1880. Però ara ha resorgit, ja que les imatges, molt treballades, que dona són úniques, màgiques i i irrepetibles.
Sobre la Plaubel Makina II:
www.flickr.com/photos/7455207@N05/30643569947
====================================================
The Plaubel Makina II is a large format press camera from the 30's to 50's, strut-folding. It used 6.5x9cm glass plates but also 120 format backs, as this one.
Dark glass ambrotype in 4x5 format, made with a Graflex Pacemaker Speed Graphic (from 1949); Kodak Anastigmat f4.5 lens; Old Workhorse collodion by Franalog.
The collodion plates are made covering a glass plate or black metal plate with collodion and salts of cadmium and / or potassium, sensitized with silver nitrate. Then you have to take the photo and reveal it in about 5 minutes, before the emulsion dries. It is one of the oldest photographic processes in the World, invented in 1851, and which dominated photography until 1880. But now it has resurfaced, as the images, very elaborate to create, that it gives are unique, razor sharp, magical and unrepeatable.
About the Plaubel Makina II:
www.flickr.com/photos/7455207@N05/30643569947
en.wikipedia.org/wiki/Collodion_process
intrepidcamera.co.uk/blog/rikard-osterlund-guide-to-wet-p...
Els camells (Camelus) són un gènere de mamífers quadrúpedes de la família dels camèlids, grup que també inclou les llames i els guanacs, entre d'altres. Com tots els camèlids, els camells són artiodàctils, o ungulats amb un nombre parell de peülles. Se'n distingeixen dues espècies vivents, cadascuna amb un nombre diferent de geps: el dromedari i el camell bactrià. El nom camell prové de l'hebreu gamal, que significa 'retornar' o 'compensar', ja que el camell fa generalment el que el seu amo li sol·licita. La paraula arribà al català mitjançant el llatí camēlus i aquest del grec kámēlos.
Tot i ser originaris dels deserts d'Àsia, fa mil·lennis que s'estengueren a Àfrica, particularment al desert del Sàhara. En temps molt més recents, han estat introduïts pels humans a les regions àrides del centre d'Austràlia, on n'hi ha poblacions ferals. Són especialment cèlebres pels seus característics geps, que són reserves de teixit adipós i els ajuden a resistir millor les temperatures elevades i per la seva gran capacitat de sobreviure molt de temps sense aigua. Els camells foren domesticats fa relativament poc temps, vers el 2000 aC.
Tot i que existeixen actualment uns 15,5 milions de camells, estan gairebé extints com a animals salvatges. Els 14 milions de dromedaris del món són tots domèstics, mentre que dels aproximadament 1,5 milions de camells bactrians, es creu que només uns 1.000 són salvatges i viuen al desert del Gobi a la Xina i Mongòlia.
Hi ha dues espècies vivents de camells: el bactrià (Camelus bactrianus), proveït de dues gepes i el dromedari (Camelus dromedarius), que té una sola gepa. Ambdues espècies són remugants sense banyes, sense morro, amb els orificis nasals formant obertures obliqües, el llavi superior dividit i movible separadament i extensible, sense peülles (tenen dos dits diferenciats), l'abdomen elevat i potes llargues i primes. Al contrari del que diu la creença popular, el camell emmagatzema greix en comptes d'aigua a la gepa, que sol caure cap a un costat en trobar-se sense reserves.
Una cosa particular és que molt poca gent sap que els camells són originaris d'Amèrica i migraren a Euràsia i l'Àfrica gràcies a les glaciacions, com ho evidencia l'abundant registre fòssil de camells a Amèrica. El fòssil de camell més antic descobert fou trobat a Kansas a mitjans de la dècada del 1930.
Imatge escanejada.
La Kodak Medalist I és una càmera impressionant. Pesada, ferma i (aquesta sí) construida com un tanc, també compta amb una magnífica optica i acabats. Probablement és la càmera de més qualitat que mai va sortir de Kodak a Rochester. Tant per estètica (obra del famós Walter Teague) com per construcció, sembla l'equivalent fotografic els grans Chevrolet o GMC dels anys 40.
Tot i que el diseny original és civil, del 1941, l'inici de la Segona Guerra Mundial feu que les seves caracteristiques (robustessa + gran qualitat de fotografía) fossin ideals per als militars americans, en especial la US Navy. Per tant és pràcticament la única camera que es produí durant la guerra, anant en principi tota la producció a les forces armades. Després de la guerra es fabricà la Medalist II, molt similar i ja per a el mercat civil de post-guerra. El gran objectiu extensible inicialment era metalitzat, però ràpidament passà a un acabat anoditzat negre per resistir l'ambient marí de la flota. L'objectiu és un Kodak Ektar f3,5 100mm en un obturador Kodak Supermatic No.2. Per tant tota la càmera és completament americana i Kodak. Fins hi tot una placa a la part posterior remarca que és "Made in the United States of America", quant totes les càmeres de gran qualitat el mercat (Leica, Contax....) eren alemanes, es a dir, del enemic.
Aquest exemplar sembla produit el 1944, per el nº de serie del objectiu, EE (es a dir 44 segons el codi Kodak).
====================
The Kodak Medalist I is an impressive camera. Heavy, solid, and built like a Sherman tank, also has a magnificent optics and rangefinder. It is probably the highest quality camera that never came out of Kodak at Rochester. Both for aesthetics (the work of the famous Walter D. Teague) and construction, it looks like the photographic equivalent of the great Chevrolet or GMC's of the 40s.
Although the original design was made for the civilan market in 1941, the beginning of World War II made its features (robustness + high quality photography) ideal for the American military, especially the US Navy. Therefore it is practically the only camera that continued production during the war, going probably all the stock to the armed forces. After the war the Medalist II, very similar but oriented to the post-war civillian market, was made. The large extensible lens was originally metallized, but quickly changed to an anodized black finish to resist the marine environment in the Navy. The lens itself is a Kodak Ektar f3.5 100mm in a Kodak Supermatic No.2 leaf shutter. Therefore, the whole camera is completely American and Kodak. Even a plaque on the back emphasizes that it is "Made in the United States of America," when all the high quality cameras (Leica, Contax ....) were of German origin, that is, the enemy.
This one appears to have been produced in 1944, for the serial number of the target, EE (ie 44 according to the Kodak code). It uses 620 roll film, which could be made respooling 120 film into 620 spools.
camera-wiki.org/wiki/Kodak_Medalist
www.filmshooterscollective.com/analog-film-photography-bl...
photojottings.com/kodak-medalist-and-fuji-gw690iii-compar...
First a Coast Guard boat roared by with sirens blasting (which I did not photograph), then a fire boat, and then a police boat. Something was happening on the south branch of the Chicago River. Alas, we were going the other way.
Chicago River
Chicago, Illinois 41.885898, -87.637597
This picture was redone
www.flickr.com/photos/jimfrazier/21868003785/
Background slightly softened, boat brighter and sharpened, using the subject mask in lightroom, color balance warmed
---
The Christopher Wheatley is a fireboat delivered to the Chicago Fire Department in 2011. When she was delivered in April 2011, she was the first new fireboat to serve the city in sixty years.
The vessel was built in Wheatley, Ontario, and was named after a young Chicago firefighter who had died in the line of duty in August 2010. Wheatley was the first Chicago firefighter to die on the job since 1998.
The vessel was designed specifically to function in an environment like Chicago, where she would be required to navigate shallow rivers, and pass under low bridges. She has four diesel engines, two of which are dedicated to powering her four water cannons. A water cannon on her aft deck is on an extensible mast that can be raised to a height of 30 feet, if required, but can be lowered to pass under low bridges. Her radio mast can also be lowered, for passing under low bridges.
en.wikipedia.org/wiki/Christopher_Wheatley
COPYRIGHT 2015, 2022 by JimFrazier All Rights Reserved. This may NOT be used for ANY reason without written consent from Jim Frazier.
150620cd7000-90201366x768
A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος anisos, "unequal" and πτερόν pteron, "wing", because the hindwing is broader than the forewing). Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Dragonflies can be mistaken for the related group, damselflies (Zygoptera), which are similar in structure, though usually lighter in build; however, the wings of most dragonflies are held flat and away from the body, while damselflies hold their wings folded at rest, along or above the abdomen. Dragonflies are agile fliers, while damselflies have a weaker, fluttery flight. Many dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. An adult dragonfly's compound eyes have nearly 24,000 ommatidia each.
Fossils of very large dragonfly-like insects, sometimes called griffinflies, are found from 325 million years ago (Mya) in Upper Carboniferous rocks; these had wingspans up to about 750 mm (30 in), but were only distant ancestors, not true dragonflies. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threatens dragonfly populations around the world.
Dragonflies are predators, both in their aquatic nymphs stage (also known as naiads) and as adults. In some species, the nymphal stage lasts for up to five years, and the adult stage may be as long as ten weeks, but most species have an adult lifespan in the order of five weeks or less, and some survive for only a few days. They are fast, agile fliers, sometimes migrating across oceans, and often live near water. They have a uniquely complex mode of reproduction involving indirect insemination, delayed fertilization, and sperm competition. During mating, the male grasps the female at the back of the head, and the female curls her abdomen under her body to pick up sperm from the male's secondary genitalia at the front of his abdomen, forming the "heart" or "wheel" posture.
Dragonflies are represented in human culture on artefacts such as pottery, rock paintings, statues and Art Nouveau jewellery. They are used in traditional medicine in Japan and China, and caught for food in Indonesia. They are symbols of courage, strength, and happiness in Japan, but seen as sinister in European folklore. Their bright colours and agile flight are admired in the poetry of Lord Tennyson and the prose of H. E. Bates.
Evolution
Dragonflies and their relatives are similar in structure to an ancient group, meganisoptera, from the 325 Mya Upper Carboniferous of Europe, a group that included the largest insect that ever lived, Meganeuropsis permiana from the Early Permian, with a wingspan around 750 mm (30 in);. Known informally as "griffinflies", their fossil record ends with the Permian–Triassic extinction event (about 247 Mya). The Protanisoptera, another ancestral group that lacks certain wing vein characters found in modern Odonata, lived from the Early to Late Permian age until the end Permian event, and are known from fossil wings from current-day United States, Russia, and Australia, suggesting they might have been cosmopolitan in distribution. While both of those groups are sometimes referred to as "giant dragonflies", in fact true dragonflies/odonata are more modern insects that had not evolved yet.
Modern dragonflies do retain some traits of their distant predecessors, and are in a group known as palaeoptera, ancient-winged. They, like the gigantic pre-dinosaur griffinflies, lack the ability to fold their wings up against their bodies in the way modern insects do, although some evolved their own different way to do so. The forerunners of modern Odonata are included in a clade called the Panodonata, which include the basal Zygoptera (damselflies) and the Anisoptera (true dragonflies). Today, some 3,000 species are extant around the world.
The relationships of anisopteran families are not fully resolved as of 2013, but all the families are monophyletic except the Corduliidae; the Gomphidae are a sister taxon to all other Anisoptera, the Austropetaliidae are sister to the Aeshnoidea, and the Chlorogomphidae are sister to a clade that includes the Synthemistidae and Libellulidae. On the cladogram, dashed lines indicate unresolved relationships; English names are given (in parentheses)
Distribution and diversity
About 3,012 species of dragonflies were known in 2010; these are classified into 348 genera in 11 families. The distribution of diversity within the biogeographical regions are summarized below (the world numbers are not ordinary totals, as overlaps in species occur).
Dragonflies live on every continent except Antarctica. In contrast to the damselflies (Zygoptera), which tend to have restricted distributions, some genera and species are spread across continents. For example, the blue-eyed darner Rhionaeschna multicolor lives all across North America, and in Central America; emperors Anax live throughout the Americas from as far north as Newfoundland to as far south as Bahia Blanca in Argentina, across Europe to central Asia, North Africa, and the Middle East. The globe skimmer Pantala flavescens is probably the most widespread dragonfly species in the world; it is cosmopolitan, occurring on all continents in the warmer regions. Most Anisoptera species are tropical, with far fewer species in temperate regions.
Some dragonflies, including libellulids and aeshnids, live in desert pools, for example in the Mojave Desert, where they are active in shade temperatures between 18 and 45 °C (64.4 to 113 °F); these insects were able to survive body temperatures above the thermal death point of insects of the same species in cooler places.
Dragonflies live from sea level up to the mountains, decreasing in species diversity with altitude. Their altitudinal limit is about 3700 m, represented by a species of Aeshna in the Pamirs.
Dragonflies become scarce at higher latitudes. They are not native to Iceland, but individuals are occasionally swept in by strong winds, including a Hemianax ephippiger native to North Africa, and an unidentified darter species. In Kamchatka, only a few species of dragonfly including the treeline emerald Somatochlora arctica and some aeshnids such as Aeshna subarctica are found, possibly because of the low temperature of the lakes there. The treeline emerald also lives in northern Alaska, within the Arctic Circle, making it the most northerly of all dragonflies.
General description
Dragonflies (suborder Anisoptera) are heavy-bodied, strong-flying insects that hold their wings horizontally both in flight and at rest. By contrast, damselflies (suborder Zygoptera) have slender bodies and fly more weakly; most species fold their wings over the abdomen when stationary, and the eyes are well separated on the sides of the head.
An adult dragonfly has three distinct segments, the head, thorax, and abdomen, as in all insects. It has a chitinous exoskeleton of hard plates held together with flexible membranes. The head is large with very short antennae. It is dominated by the two compound eyes, which cover most of its surface. The compound eyes are made up of ommatidia, the numbers being greater in the larger species. Aeshna interrupta has 22650 ommatidia of two varying sizes, 4500 being large. The facets facing downward tend to be smaller. Petalura gigantea has 23890 ommatidia of just one size. These facets provide complete vision in the frontal hemisphere of the dragonfly. The compound eyes meet at the top of the head (except in the Petaluridae and Gomphidae, as also in the genus Epiophlebia). Also, they have three simple eyes or ocelli. The mouthparts are adapted for biting with a toothed jaw; the flap-like labrum, at the front of the mouth, can be shot rapidly forward to catch prey. The head has a system for locking it in place that consists of muscles and small hairs on the back of the head that grip structures on the front of the first thoracic segment. This arrester system is unique to the Odonata, and is activated when feeding and during tandem flight.
The thorax consists of three segments as in all insects. The prothorax is small and is flattened dorsally into a shield-like disc, which has two transverse ridges. The mesothorax and metathorax are fused into a rigid, box-like structure with internal bracing, and provide a robust attachment for the powerful wing muscles inside. The thorax bears two pairs of wings and three pairs of legs. The wings are long, veined, and membranous, narrower at the tip and wider at the base. The hindwings are broader than the forewings and the venation is different at the base. The veins carry haemolymph, which is analogous to blood in vertebrates, and carries out many similar functions, but which also serves a hydraulic function to expand the body between nymphal stages (instars) and to expand and stiffen the wings after the adult emerges from the final nymphal stage. The leading edge of each wing has a node where other veins join the marginal vein, and the wing is able to flex at this point. In most large species of dragonflies, the wings of females are shorter and broader than those of males. The legs are rarely used for walking, but are used to catch and hold prey, for perching, and for climbing on plants. Each has two short basal joints, two long joints, and a three-jointed foot, armed with a pair of claws. The long leg joints bear rows of spines, and in males, one row of spines on each front leg is modified to form an "eyebrush", for cleaning the surface of the compound eye.
The abdomen is long and slender and consists of 10 segments. Three terminal appendages are on segment 10; a pair of superiors (claspers) and an inferior. The second and third segments are enlarged, and in males, on the underside of the second segment has a cleft, forming the secondary genitalia consisting of the lamina, hamule, genital lobe, and penis. There are remarkable variations in the presence and the form of the penis and the related structures, the flagellum, cornua, and genital lobes. Sperm is produced at the 9th segment, and is transferred to the secondary genitalia prior to mating. The male holds the female behind the head using a pair of claspers on the terminal segment. In females, the genital opening is on the underside of the eighth segment, and is covered by a simple flap (vulvar lamina) or an ovipositor, depending on species and the method of egg-laying. Dragonflies having simple flaps shed the eggs in water, mostly in flight. Dragonflies having ovipositors use them to puncture soft tissues of plants and place the eggs singly in each puncture they make.
Dragonfly nymphs vary in form with species, and are loosely classed into claspers, sprawlers, hiders, and burrowers. The first instar is known as a prolarva, a relatively inactive stage from which it quickly moults into the more active nymphal form. The general body plan is similar to that of an adult, but the nymph lacks wings and reproductive organs. The lower jaw has a huge, extensible labium, armed with hooks and spines, which is used for catching prey. This labium is folded under the body at rest and struck out at great speed by hydraulic pressure created by the abdominal muscles. Whereas damselfly nymphs have three feathery external gills, dragonfly nymphs have internal gills, located around the fourth and fifth abdominal segments. Water is pumped in and out of the abdomen through an opening at the tip. The naiads of some clubtails (Gomphidae) that burrow into the sediment, have a snorkel-like tube at the end of the abdomen enabling them to draw in clean water while they are buried in mud. Naiads can forcefully expel a jet of water to propel themselves with great rapidity.
Colouration
Many adult dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. Their overall colouration is often a combination of yellow, red, brown, and black pigments, with structural colours. Blues are typically created by microstructures in the cuticle that reflect blue light. Greens often combine a structural blue with a yellow pigment. Freshly emerged adults, known as tenerals, are often pale-coloured and obtain their typical colours after a few days, some have their bodies covered with a pale blue, waxy powderiness called pruinosity; it wears off when scraped during mating, leaving darker areas.
Some dragonflies, such as the green darner, Anax junius, have a noniridescent blue that is produced structurally by scatter from arrays of tiny spheres in the endoplasmic reticulum of epidermal cells underneath the cuticle.
The wings of dragonflies are generally clear, apart from the dark veins and pterostigmata. In the chasers (Libellulidae), however, many genera have areas of colour on the wings: for example, groundlings (Brachythemis) have brown bands on all four wings, while some scarlets (Crocothemis) and dropwings (Trithemis) have bright orange patches at the wing bases. Some aeshnids such as the brown hawker (Aeshna grandis) have translucent, pale yellow wings.
Dragonfly nymphs are usually a well-camouflaged blend of dull brown, green, and grey.
Biology
Ecology
Dragonflies and damselflies are predatory both in the aquatic nymphal and adult stages. Nymphs feed on a range of freshwater invertebrates and larger ones can prey on tadpoles and small fish. Adults capture insect prey in the air, making use of their acute vision and highly controlled flight. The mating system of dragonflies is complex, and they are among the few insect groups that have a system of indirect sperm transfer along with sperm storage, delayed fertilization, and sperm competition.
Adult males vigorously defend territories near water; these areas provide suitable habitat for the nymphs to develop, and for females to lay their eggs. Swarms of feeding adults aggregate to prey on swarming prey such as emerging flying ants or termites.
Dragonflies as a group occupy a considerable variety of habitats, but many species, and some families, have their own specific environmental requirements. Some species prefer flowing waters, while others prefer standing water. For example, the Gomphidae (clubtails) live in running water, and the Libellulidae (skimmers) live in still water. Some species live in temporary water pools and are capable of tolerating changes in water level, desiccation, and the resulting variations in temperature, but some genera such as Sympetrum (darters) have eggs and nymphs that can resist drought and are stimulated to grow rapidly in warm, shallow pools, also often benefiting from the absence of predators there. Vegetation and its characteristics including submerged, floating, emergent, or waterside are also important. Adults may require emergent or waterside plants to use as perches; others may need specific submerged or floating plants on which to lay eggs. Requirements may be highly specific, as in Aeshna viridis (green hawker), which lives in swamps with the water-soldier, Stratiotes aloides. The chemistry of the water, including its trophic status (degree of enrichment with nutrients) and pH can also affect its use by dragonflies. Most species need moderate conditions, not too eutrophic, not too acidic; a few species such as Sympetrum danae (black darter) and Libellula quadrimaculata (four-spotted chaser) prefer acidic waters such as peat bogs, while others such as Libellula fulva (scarce chaser) need slow-moving, eutrophic waters with reeds or similar waterside plants.
Behaviour
Many dragonflies, particularly males, are territorial. Some defend a territory against others of their own species, some against other species of dragonfly and a few against insects in unrelated groups. A particular perch may give a dragonfly a good view over an insect-rich feeding ground; males of many species such as the Pachydiplax longipennis (blue dasher) jostle other dragonflies to maintain the right to alight there. Defending a breeding territory is common among male dragonflies, especially in species that congregate around ponds. The territory contains desirable features such as a sunlit stretch of shallow water, a special plant species, or the preferred substrate for egg-laying. The territory may be small or large, depending on its quality, the time of day, and the number of competitors, and may be held for a few minutes or several hours. Dragonflies including Tramea lacerata (black saddlebags) may notice landmarks that assist in defining the boundaries of the territory. Landmarks may reduce the costs of territory establishment, or might serve as a spatial reference. Some dragonflies signal ownership with striking colours on the face, abdomen, legs, or wings. The Plathemis lydia (common whitetail) dashes towards an intruder holding its white abdomen aloft like a flag. Other dragonflies engage in aerial dogfights or high-speed chases. A female must mate with the territory holder before laying her eggs. There is also conflict between the males and females. Females may sometimes be harassed by males to the extent that it affects their normal activities including foraging and in some dimorphic species females have evolved multiple forms with some forms appearing deceptively like males. In some species females have evolved behavioural responses such as feigning death to escape the attention of males. Similarly, selection of habitat by adult dragonflies is not random, and terrestrial habitat patches may be held for up to 3 months. A species tightly linked to its birth site utilises a foraging area that is several orders of magnitude larger than the birth site.
Reproduction
Mating in dragonflies is a complex, precisely choreographed process. First, the male has to attract a female to his territory, continually driving off rival males. When he is ready to mate, he transfers a packet of sperm from his primary genital opening on segment 9, near the end of his abdomen, to his secondary genitalia on segments 2–3, near the base of his abdomen. The male then grasps the female by the head with the claspers at the end of his abdomen; the structure of the claspers varies between species, and may help to prevent interspecific mating. The pair flies in tandem with the male in front, typically perching on a twig or plant stem. The female then curls her abdomen downwards and forwards under her body to pick up the sperm from the male's secondary genitalia, while the male uses his "tail" claspers to grip the female behind the head: this distinctive posture is called the "heart" or "wheel"; the pair may also be described as being "in cop".
Egg-laying (ovipositing) involves not only the female darting over floating or waterside vegetation to deposit eggs on a suitable substrate, but also the male hovering above her or continuing to clasp her and flying in tandem. The male attempts to prevent rivals from removing his sperm and inserting their own, something made possible by delayed fertilisation and driven by sexual selection. If successful, a rival male uses his penis to compress or scrape out the sperm inserted previously; this activity takes up much of the time that a copulating pair remains in the heart posture. Flying in tandem has the advantage that less effort is needed by the female for flight and more can be expended on egg-laying, and when the female submerges to deposit eggs, the male may help to pull her out of the water.
Egg-laying takes two different forms depending on the species. The female in some families has a sharp-edged ovipositor with which she slits open a stem or leaf of a plant on or near the water, so she can push her eggs inside. In other families such as clubtails (Gomphidae), cruisers (Macromiidae), emeralds (Corduliidae), and skimmers (Libellulidae), the female lays eggs by tapping the surface of the water repeatedly with her abdomen, by shaking the eggs out of her abdomen as she flies along, or by placing the eggs on vegetation. In a few species, the eggs are laid on emergent plants above the water, and development is delayed until these have withered and become immersed.
Life cycle
Dragonflies are hemimetabolous insects; they do not have a pupal stage and undergo an incomplete metamorphosis with a series of nymphal stages from which the adult emerges. Eggs laid inside plant tissues are usually shaped like grains of rice, while other eggs are the size of a pinhead, ellipsoidal, or nearly spherical. A clutch may have as many as 1500 eggs, and they take about a week to hatch into aquatic nymphs or naiads which moult between six and 15 times (depending on species) as they grow. Most of a dragonfly's life is spent as a nymph, beneath the water's surface. The nymph extends its hinged labium (a toothed mouthpart similar to a lower mandible, which is sometimes termed as a "mask" as it is normally folded and held before the face) that can extend forward and retract rapidly to capture prey such as mosquito larvae, tadpoles, and small fish. They breathe through gills in their rectum, and can rapidly propel themselves by suddenly expelling water through the anus. Some naiads, such as the later stages of Antipodophlebia asthenes, hunt on land.
The nymph stage of dragonflies lasts up to five years in large species, and between two months and three years in smaller species. When the naiad is ready to metamorphose into an adult, it stops feeding and makes its way to the surface, generally at night. It remains stationary with its head out of the water, while its respiration system adapts to breathing air, then climbs up a reed or other emergent plant, and moults (ecdysis). Anchoring itself firmly in a vertical position with its claws, its skin begins to split at a weak spot behind the head. The adult dragonfly crawls out of its nymph skin, the exuvia, arching backwards when all but the tip of its abdomen is free, to allow its exoskeleton to harden. Curling back upwards, it completes its emergence, swallowing air, which plumps out its body, and pumping haemolymph into its wings, which causes them to expand to their full extent.
Dragonflies in temperate areas can be categorized into two groups, an early group and a later one. In any one area, individuals of a particular "spring species" emerge within a few days of each other. The springtime darner (Basiaeschna janata), for example, is suddenly very common in the spring, but disappears a few weeks later and is not seen again until the following year. By contrast, a "summer species" emerges over a period of weeks or months, later in the year. They may be seen on the wing for several months, but this may represent a whole series of individuals, with new adults hatching out as earlier ones complete their lifespans.
Sex ratios
The sex ratio of male to female dragonflies varies both temporally and spatially. Adult dragonflies have a high male-biased ratio at breeding habitats. The male-bias ratio has contributed partially to the females using different habitats to avoid male harassment. As seen in Hine's emerald dragonfly (Somatochlora hineana), male populations use wetland habitats, while females use dry meadows and marginal breeding habitats, only migrating to the wetlands to lay their eggs or to find mating partners. Unwanted mating is energetically costly for females because it affects the amount of time that they are able to spend foraging.
Flight
Dragonflies are powerful and agile fliers, capable of migrating across the sea, moving in any direction, and changing direction suddenly. In flight, the adult dragonfly can propel itself in six directions: upward, downward, forward, backward, to left and to right. They have four different styles of flight: A number of flying modes are used that include counter-stroking, with forewings beating 180° out of phase with the hindwings, is used for hovering and slow flight. This style is efficient and generates a large amount of lift; phased-stroking, with the hindwings beating 90° ahead of the forewings, is used for fast flight. This style creates more thrust, but less lift than counter-stroking; synchronised-stroking, with forewings and hindwings beating together, is used when changing direction rapidly, as it maximises thrust; and gliding, with the wings held out, is used in three situations: free gliding, for a few seconds in between bursts of powered flight; gliding in the updraft at the crest of a hill, effectively hovering by falling at the same speed as the updraft; and in certain dragonflies such as darters, when "in cop" with a male, the female sometimes simply glides while the male pulls the pair along by beating his wings.
The wings are powered directly, unlike most families of insects, with the flight muscles attached to the wing bases. Dragonflies have a high power/weight ratio, and have been documented accelerating at 4 G linearly and 9 G in sharp turns while pursuing prey.
Dragonflies generate lift in at least four ways at different times, including classical lift like an aircraft wing; supercritical lift with the wing above the critical angle, generating high lift and using very short strokes to avoid stalling; and creating and shedding vortices. Some families appear to use special mechanisms, as for example the Libellulidae which take off rapidly, their wings beginning pointed far forward and twisted almost vertically. Dragonfly wings behave highly dynamically during flight, flexing and twisting during each beat. Among the variables are wing curvature, length and speed of stroke, angle of attack, forward/back position of wing, and phase relative to the other wings.
Flight speed
Old and unreliable claims are made that dragonflies such as the southern giant darner can fly up to 97 km/h (60 mph). However, the greatest reliable flight speed records are for other types of insects. In general, large dragonflies like the hawkers have a maximum speed of 36–54 km/h (22–34 mph) with average cruising speed of about 16 km/h (9.9 mph). Dragonflies can travel at 100 body-lengths per second in forward flight, and three lengths per second backwards.
Motion camouflage
n high-speed territorial battles between male Australian emperors (Hemianax papuensis), the fighting dragonflies adjust their flight paths to appear stationary to their rivals, minimizing the chance of being detected as they approach.[a] To achieve the effect, the attacking dragonfly flies towards his rival, choosing his path to remain on a line between the rival and the start of his attack path. The attacker thus looms larger as he closes on the rival, but does not otherwise appear to move. Researchers found that six of 15 encounters involved motion camouflage.
Temperature control
The flight muscles need to be kept at a suitable temperature for the dragonfly to be able to fly. Being cold-blooded, they can raise their temperature by basking in the sun. Early in the morning, they may choose to perch in a vertical position with the wings outstretched, while in the middle of the day, a horizontal stance may be chosen. Another method of warming up used by some larger dragonflies is wing-whirring, a rapid vibration of the wings that causes heat to be generated in the flight muscles. The green darner (Anax junius) is known for its long-distance migrations, and often resorts to wing-whirring before dawn to enable it to make an early start.
Becoming too hot is another hazard, and a sunny or shady position for perching can be selected according to the ambient temperature. Some species have dark patches on the wings which can provide shade for the body, and a few use the obelisk posture to avoid overheating. This behaviour involves doing a "handstand", perching with the body raised and the abdomen pointing towards the sun, thus minimising the amount of solar radiation received. On a hot day, dragonflies sometimes adjust their body temperature by skimming over a water surface and briefly touching it, often three times in quick succession. This may also help to avoid desiccation.
Feeding
Adult dragonflies hunt on the wing using their exceptionally acute eyesight and strong, agile flight. They are almost exclusively carnivorous, eating a wide variety of insects ranging from small midges and mosquitoes to butterflies, moths, damselflies, and smaller dragonflies. A large prey item is subdued by being bitten on the head and is carried by the legs to a perch. Here, the wings are discarded and the prey usually ingested head first. A dragonfly may consume as much as a fifth of its body weight in prey per day. Dragonflies are also some of the insect world's most efficient hunters, catching up to 95% of the prey they pursue.
The nymphs are voracious predators, eating most living things that are smaller than they are. Their staple diet is mostly bloodworms and other insect larvae, but they also feed on tadpoles and small fish. A few species, especially those that live in temporary waters, are likely to leave the water to feed. Nymphs of Cordulegaster bidentata sometimes hunt small arthropods on the ground at night, while some species in the Anax genus have even been observed leaping out of the water to attack and kill full-grown tree frogs.
Eyesight
Dragonfly vision is thought to be like slow motion for humans. Dragonflies see faster than we do; they see around 200 images per second. A dragonfly can see in 360 degrees, and nearly 80 percent of the insect's brain is dedicated to its sight.
Predators
Although dragonflies are swift and agile fliers, some predators are fast enough to catch them. These include falcons such as the American kestrel, the merlin, and the hobby; nighthawks, swifts, flycatchers and swallows also take some adults; some species of wasps, too, prey on dragonflies, using them to provision their nests, laying an egg on each captured insect. In the water, various species of ducks and herons eat dragonfly nymphs and they are also preyed on by newts, frogs, fish, and water spiders. Amur falcons, which migrate over the Indian Ocean at a period that coincides with the migration of the globe skimmer dragonfly, Pantala flavescens, may actually be feeding on them while on the wing.
Parasites
Dragonflies are affected by three major groups of parasites: water mites, gregarine protozoa, and trematode flatworms (flukes). Water mites, Hydracarina, can kill smaller dragonfly nymphs, and may also be seen on adults. Gregarines infect the gut and may cause blockage and secondary infection. Trematodes are parasites of vertebrates such as frogs, with complex life cycles often involving a period as a stage called a cercaria in a secondary host, a snail. Dragonfly nymphs may swallow cercariae, or these may tunnel through a nymph's body wall; they then enter the gut and form a cyst or metacercaria, which remains in the nymph for the whole of its development. If the nymph is eaten by a frog, the amphibian becomes infected by the adult or fluke stage of the trematode.
Dragonflies and humans
Conservation
Most odonatologists live in temperate areas and the dragonflies of North America and Europe have been the subject of much research. However, the majority of species live in tropical areas and have been little studied. With the destruction of rainforest habitats, many of these species are in danger of becoming extinct before they have even been named. The greatest cause of decline is forest clearance with the consequent drying up of streams and pools which become clogged with silt. The damming of rivers for hydroelectric schemes and the drainage of low-lying land has reduced suitable habitat, as has pollution and the introduction of alien species.
In 1997, the International Union for Conservation of Nature set up a status survey and conservation action plan for dragonflies. This proposes the establishment of protected areas around the world and the management of these areas to provide suitable habitat for dragonflies. Outside these areas, encouragement should be given to modify forestry, agricultural, and industrial practices to enhance conservation. At the same time, more research into dragonflies needs to be done, consideration should be given to pollution control and the public should be educated about the importance of biodiversity.
Habitat degradation has reduced dragonfly populations across the world, for example in Japan. Over 60% of Japan's wetlands were lost in the 20th century, so its dragonflies now depend largely on rice fields, ponds, and creeks. Dragonflies feed on pest insects in rice, acting as a natural pest control. Dragonflies are steadily declining in Africa, and represent a conservation priority.
The dragonfly's long lifespan and low population density makes it vulnerable to disturbance, such as from collisions with vehicles on roads built near wetlands. Species that fly low and slow may be most at risk.
Dragonflies are attracted to shiny surfaces that produce polarization which they can mistake for water, and they have been known to aggregate close to polished gravestones, solar panels, automobiles, and other such structures on which they attempt to lay eggs. These can have a local impact on dragonfly populations; methods of reducing the attractiveness of structures such as solar panels are under experimentation.
In culture
A blue-glazed faience dragonfly amulet was found by Flinders Petrie at Lahun, from the Late Middle Kingdom of ancient Egypt.
Many Native American tribes consider dragonflies to be medicine animals that had special powers. For example, the southwestern tribes, including the Pueblo, Hopi, and Zuni, associated dragonflies with transformation. They referred to dragonflies as "snake doctors" because they believed dragonflies followed snakes into the ground and healed them if they were injured. For the Navajo, dragonflies symbolize pure water. Often stylized in a double-barred cross design, dragonflies are a common motif in Zuni pottery, as well as Hopi rock art and Pueblo necklaces.: 20–26
As a seasonal symbol in Japan, the dragonflies are associated with season of autumn. In Japan, they are symbols of rebirth, courage, strength, and happiness. They are also depicted frequently in Japanese art and literature, especially haiku poetry. Japanese children catch large dragonflies as a game, using a hair with a small pebble tied to each end, which they throw into the air. The dragonfly mistakes the pebbles for prey, gets tangled in the hair, and is dragged to the ground by the weight.: 38
In Chinese culture, dragonflies symbolize both change and instability. They are also symbols in the Chinese practices of Feng Shui, where placements of dragonfly statues and artwork in parts of a home or office are believed to bring new insights and positive changes.
In both China and Japan, dragonflies have been used in traditional medicine. In Indonesia, adult dragonflies are caught on poles made sticky with birdlime, then fried in oil as a delicacy.
Images of dragonflies are common in Art Nouveau, especially in jewellery designs. They have also been used as a decorative motif on fabrics and home furnishings. Douglas, a British motorcycle manufacturer based in Bristol, named its innovatively designed postwar 350-cc flat-twin model the Dragonfly.
Among the classical names of Japan are Akitsukuni (秋津国), Akitsushima (秋津島), Toyo-akitsushima (豊秋津島). Akitsu is an old word for dragonfly, so one interpretation of Akitsushima is "Dragonfly Island". This is attributed to a legend in which Japan's mythical founder, Emperor Jimmu, was bitten by a mosquito, which was then eaten by a dragonfly.
In Europe, dragonflies have often been seen as sinister. Some English vernacular names, such as "horse-stinger", "devil's darning needle", and "ear cutter", link them with evil or injury. Swedish folklore holds that the devil uses dragonflies to weigh people's souls.: 25–27 The Norwegian name for dragonflies is Øyenstikker ("eye-poker"), and in Portugal, they are sometimes called tira-olhos ("eyes-snatcher"). They are often associated with snakes, as in the Welsh name gwas-y-neidr, "adder's servant". The Southern United States terms "snake doctor" and "snake feeder" refer to a folk belief that dragonflies catch insects for snakes or follow snakes around and stitch them back together if they are injured. Interestingly, the Hungarian name for dragonfly is szitakötő ("sieve-knitter").
The watercolourist Moses Harris (1731–1785), known for his The Aurelian or natural history of English insects (1766), published in 1780, the first scientific descriptions of several Odonata including the banded demoiselle, Calopteryx splendens. He was the first English artist to make illustrations of dragonflies accurate enough to be identified to species (Aeshna grandis at top left of plate illustrated), though his rough drawing of a nymph (at lower left) with the mask extended appears to be plagiarised.[b]
More recently, dragonfly watching has become popular in America as some birdwatchers seek new groups to observe.
In heraldry, like other winged insects, the dragonfly is typically depicted tergiant (with its back facing the viewer), with its head to chief.
In poetry and literature
Lafcadio Hearn wrote in his 1901 book A Japanese Miscellany that Japanese poets had created dragonfly haiku "almost as numerous as are the dragonflies themselves in the early autumn." The poet Matsuo Bashō (1644–1694) wrote haiku such as "Crimson pepper pod / add two pairs of wings, and look / darting dragonfly", relating the autumn season to the dragonfly. Hori Bakusui (1718–1783) similarly wrote "Dyed he is with the / Colour of autumnal days, / O red dragonfly."
The poet Lord Tennyson, described a dragonfly splitting its old skin and emerging shining metallic blue like "sapphire mail" in his 1842 poem "The Two Voices", with the lines "An inner impulse rent the veil / Of his old husk: from head to tail / Came out clear plates of sapphire mail."
The novelist H. E. Bates described the rapid, agile flight of dragonflies in his 1937 nonfiction book Down the River:
I saw, once, an endless procession, just over an area of water-lilies, of small sapphire dragonflies, a continuous play of blue gauze over the snowy flowers above the sun-glassy water. It was all confined, in true dragonfly fashion, to one small space. It was a continuous turning and returning, an endless darting, poising, striking and hovering, so swift that it was often lost in sunlight.
In technology
A dragonfly has been genetically modified with light-sensitive "steering neurons" in its nerve cord to create a cyborg-like "DragonflEye". The neurons contain genes like those in the eye to make them sensitive to light. Miniature sensors, a computer chip and a solar panel were fitted in a "backpack" over the insect's thorax in front of its wings. Light is sent down flexible light-pipes named optrodes[c] from the backpack into the nerve cord to give steering commands to the insect. The result is a "micro-aerial vehicle that's smaller, lighter and stealthier than anything else that's manmade".
[Credit: en.wikipedia.org/]
La Kodak Medalist I és una càmera impressionant. Pesada, ferma i (aquesta sí) construida com un tanc, també compta amb una magnífica optica i acabats. Probablement és la càmera de més qualitat que mai va sortir de Kodak a Rochester. Tant per estètica (obra del famós Walter Teague) com per construcció, sembla l'equivalent fotografic els grans Chevrolet o GMC dels anys 40.
Tot i que el diseny original és civil, del 1941, l'inici de la Segona Guerra Mundial feu que les seves caracteristiques (robustessa + gran qualitat de fotografía) fossin ideals per als militars americans, en especial la US Navy. Per tant és pràcticament la única camera que es produí durant la guerra, anant en principi tota la producció a les forces armades. Després de la guerra es fabricà la Medalist II, molt similar i ja per a el mercat civil de post-guerra. El gran objectiu extensible inicialment era metalitzat, però ràpidament passà a un acabat anoditzat negre per resistir l'ambient marí de la flota. L'objectiu és un Kodak Ektar f3,5 100mm en un obturador Kodak Supermatic No.2. Per tant tota la càmera és completament americana i Kodak. Fins hi tot una placa a la part posterior remarca que és "Made in the United States of America", quant totes les càmeres de gran qualitat el mercat (Leica, Contax....) eren alemanes, es a dir, del enemic.
Aquest exemplar sembla produit el 1944, per el nº de serie del objectiu, EE (es a dir 44 segons el codi Kodak).
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The Kodak Medalist I is an impressive camera. Heavy, solid, and built like a Sherman tank, also has a magnificent optics and rangefinder. It is probably the highest quality camera that never came out of Kodak at Rochester. Both for aesthetics (the work of the famous Walter D. Teague) and construction, it looks like the photographic equivalent of the great Chevrolet or GMC's of the 40s.
Although the original design was made for the civilan market in 1941, the beginning of World War II made its features (robustness + high quality photography) ideal for the American military, especially the US Navy. Therefore it is practically the only camera that continued production during the war, going probably all the stock to the armed forces. After the war the Medalist II, very similar but oriented to the post-war civillian market, was made. The large extensible lens was originally metallized, but quickly changed to an anodized black finish to resist the marine environment in the Navy. The lens itself is a Kodak Ektar f3.5 100mm in a Kodak Supermatic No.2 leaf shutter. Therefore, the whole camera is completely American and Kodak. Even a plaque on the back emphasizes that it is "Made in the United States of America," when all the high quality cameras (Leica, Contax ....) were of German origin, that is, the enemy.
This one appears to have been produced in 1944, for the serial number of the target, EE (ie 44 according to the Kodak code). It uses 620 roll film, which could be made respooling 120 film into 620 spools.
camera-wiki.org/wiki/Kodak_Medalist
www.filmshooterscollective.com/analog-film-photography-bl...
photojottings.com/kodak-medalist-and-fuji-gw690iii-compar...
La Plaubel Makina II és una càmara de gran format de meitat del s. XX, extensible i destinada sobretot a la premsa. Feia servir plaques de 6,5x9cm però s'adapta sense problemes a porta-rodets de format 120, com en el cas d'aquesta.
Les primeres Makina no tenien telèmetre, però a partir de la Makina II del 1933 ja incorpora un. Posteriorment es refinarà el model amb la Makina IIS, que facilita molt el canvi de lents, i ja després de la guerra mundial, l'ultim model és la Makina III, amb molts canvis sobretot per a disparar flaix.
De fet, aquesta que tinc és una mica inusual ja que no sembla pas una Makina IIS per tal i com està montada la lent. De fet té dues parts, amb el obturador al mig, el que fa més dificil desmontar-la. Però en canvi té les dues finestretes del telèmetre rectangulars, el que és un element distintiu de les IIS. Probablement sigui una II a la que es va reformar el telèmetre per alguna raó, o bé es tracti d'un model just de transició. El que si no milloraren fou una refotuda manera d'agafar-la. Ergonomía? no en tenien ni idea!!
En tot cas és clàrament anterior a la guerra (ja que està marcada amb el DRP "Deutsches Reich Patent" en comptes del DBP de postguerra, "Deutsches BundesPatent". Crec que fou fabricada entre el 1933 i el 1936, més aviat cap al final del periode, ja que el frontal és cromat, i inicialment es produia en negre. Potser fou una de les darreres Makina II (abans del canvi al model IIS) i per això 1936 sembla la data més probable de producció.
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The Plaubel Makina II is a large format press camera from the 30's to 50's, strut-folding. It used 6.5x9cm glass plates but also 120 format backs, as this one.
The first Makina had no rangefinder, but in 1933 the Makina II already incorporates one. Later, the model will be refined with the Makina II S, which greatly facilitates the change of lens, and even after the World War, the latest model is the Makina III, with many refinements, especially for flash synchro. What they didn't get at all was an easy way to hold it. Ergonomics, what's that??
In fact, this one that I have is a little unusual since it does not look like a Makina IIS as the lens has two parts, with the shutter in the middle, which makes it more difficult to disassemble it. But otherwise it has rangefinder rectangular windows, which is a distinctive element of the IIS. It is probably a II to which the rangefinder was reformed for some reason, or it was just a transition model.
In any case, it was clearly made before WW2 (since it is marked with the DRP "Deutsches Reich Patent" instead of the post-war DBP, "Deutsches BundesPatent.") I think it was manufactured between 1933 and 1936, rather towards the end of this period, since the front is chromed, and initially it was produced in black. Perhaps it was one of the last Makina II (before the change to the IIS model) and for that reason 1936 seems the most probable date of production.
lommen9.home.xs4all.nl/plaubel/index.html
www.earlyphotography.co.uk/site/entry_C25.html
camera-wiki.org/wiki/Plaubel_Makina#The_6.5.C3.979_rangef...
Meet Wizard!
This was taken in East Jesus (Slab City, Niland, California) (eastjesus.org/). "East Jesus is an experimental, habitable, extensible artwork in progress since 2006". It is a "refuge for artists, musicians, survivalists, writers, scientists, laymen and other wandering geniuses".
Wizard gave us our tour of the 'private' residences outside the Art Garden of East Jesus. He started the tour by telling us he is certifiably insane and hears voices all the time and was hearing them right now. He was such a story teller and enjoyed showing us around. It was such an incredible opportunity and experience!
From top left, clockwise:
Contaflex IV with extensible rubber lens hood, ca. 1956. leaf-shutter, fixed lens SLR with uncoupled non-TTL selenium meter, still functional on this camera
Contaflex III with front element replaced against a Pro-Tessar M1:1 macro lens, ca. 1956, similar to the IV but without a light meter
Voigtländer Vitomatic IIa with fixed Ultron 50/2.0 ca. 1962, fixed lens rangefinder with uncoupled selenium meter
Zeiss Ikon Voigtländer Icarex 35S TM with Voigtländer Color-Ultron 50/2.0 M42 lens, ca. 1970, SLR with TTL CdS meter
Let it not be said that I am a Leica man. Actually I am (this photo was shot using Leica gear), but I'm undergoing therapy.
IN MY GARDEN:
Chameleon:A small slow-moving Old World lizard with a prehensile tail, long extensible tongue, protruding eyes that rotate independently, and a highly developed ability to change colour.
"The hummingbird, also known as hummingbird, cuitelo, suck flower, pink-flower, suck honey, binga, Guanambi, guinumbi, guainumbi, guanumbi [1] and mainoĩ, [2] is a Trochilidae family bird, composed 108 genera and 322 known species. In Brazil, some genres are given other names, such as tails-white genre Phaethornis or straight-nozzles Heliomaster genre. In the classificatory system of Sibley & Ahlquist, the Trochilidae family was part of a proper order, the Apodiformes. Among the group's distinctive features include the elongated beak, food-based nectar, eight pairs of ribs, fourteen to fifteen cervical vertebrae, iridescent plumage and an extensible and bifurcated tongue".Fonte Wikipédia
IN ENGLISH BELOW THE LINE
La Folmer & Schwing Graflex 1A és una càmera realment espectacular i força especial. Tot i que tampoc es excesivament rara, sembla que costa de trobar-les en bon estat, tant cosmetic, com mecanic. En aquest cas vaig estar força de sort, tot i que com veureu no és perfecta ni molt menys.
La Graflex 1A és una càmera reflex de rodet (SLR) de inicis de. s. XX. Sí, una SLR de fa més de cent anys! I "mes o menys" funciona. Aquest model es produí entre el 1909 i el 1925, amb una variació que afecta a aquesta en questió el 1918. Fa servir el desaparescut format 116 (pot fer servir sense problemes format 120 amb uns senzills adaptadors) i té un obturador de pla focal horitzontal amb velocitats de fins a 1/1000. Com una inmensa Leica, vaja. L'objectiu és un Cooke Anastigmat f4.5 de 5", d'un preciós color bronze.
Pel nº de serie, sembla que fou fabricada cap al 1915-1917, però hi ha detalls de la construcció que son confosos. Per una banda porta el sistema Autographic per fer anotacions a la pel·licula, cosa que la data clàrament posterior al 1915. Però en canvi el visor és un petit puzzle. Compta amb el complex visor extensible fabricat fins al 1918, i això quadra amb el nº de serie, però en canvi la resta de l'estructura de la càmera sembla del 2on model, amb un visor simplificat i fabricada entre 1918 i 1925. De fet, aquest visor no permet tancar la tapa superior, amb el que després de desmontar-lo i analitzar-lo em sembla que és una càmera clarament post-1918, però a la que algú incorporà un visor del model antic. No entenc perquè: potser dona millor visió per cobrir el vidre esmeril·lat, però és més complex i sobretot així la càmera no tanca per dalt, apart que el visor només s'aguanta per 2 dels quatre punts d'anclatge.
Això sí, he de reconeixer que queda impresionantment més espectacular amb aquest llarg visor i el seu sistema de desplegament. Realment no pot ser més "steampunk"!!
Ah, i a nivell mecanic, l'obturador funciona prou be però el mirall no va alhora amb la cortina, excepte disparant-lo amb la càmera en vertical. Per fer fotos horitzontals cal apretar el disparador (el mirall puja) i tot seguit apretar un boto secundari que sí dispara la cortina del obturador. Amb tot, he pogut fer fotos amb aquesta càmera.
licm.org.uk/livingImage/Graflex_1A.html
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The Folmer & Schwing Graflex 1A is a truly spectacular camera and quite special indeed. Although not too rare, it seems difficult to find them in good condition, both cosmetic and mechanical. In this case, I was very lucky, although as you can see, it is not perfect at all. It has it's lot of issues.
The Graflex 1A is an early XX Century roll-film SLR camera. And "more or less" works. This model was produced between 1909 and 1925, with a small change in 1918. It's designed for the missing 116 format (can be used 120 without problems, with simple adapters) and has a horizontal focal plane shutter, with speeds of up to 1/1000. Like a huge Leica! The lens is a beautiful bronze Cooke Anastigmat f4.5 / 5".
Considering it's serial number, it looks like it was manufactured around 1915-1917, but details of the construction are confusing. On one hand, it has the Autographic system for taking notes into the film, something that dates it from 1915 on. However, the viewfinder is a small puzzle. It has the extensible viewfinder complex hood manufactured until 1918, and this element fits in with the serial number age, but instead the rest of the camera structure looks like the second model. This had a simplified viewfinder hood, without metallic scissors, and was manufactured between 1918 and 1925.
In fact , this viewfinder does not allow closing the top cover of the camera. After dismantling and analyzing the hood, it seems to me to be a clearly post-1918 camera, but to which someone incorporated an old model hood. I don't understand why: maybe it gives better vision to cover the ground glass, but it is more complex and especially so the camera does not close up. And the hood is unestable, as it only can be attached by two screws, instead of four.
Of course, I must admit that it is impressively more spectacular with this long hood and its scissors deployment system. It really can't be more "steampunk" !!
Ah, and on a mechanical level, the shutter works well enough but the mirror doesn't go with the curtain at the same time, except by shooting it with the camera upright. To take horizontal photos, you must press the shutter button (the mirror goes up) and then press a secondary button that does release the shutter curtain. Despite all these issues, I was able to take pictures with this camera.
licm.org.uk/livingImage/Graflex_1A.html
redbellows.co.uk/CameraCollection/Kodak/Graflex/Graflex1A...
Imbrium Lunokhod Industries Model VS-MU-333 'Lorikeet' is the next step in Imbrium Lunokhod Industries Frame System. This mass produced frame builds on the versatile and flexible mobile frame platform made popular by the VS-M/S-71 'Degei' (flic.kr/s/aHsm37uTTm) and the VS-MX-04 'Rangi' (flic.kr/s/aHsk4AUkEY). Developed for planetary surface operations and utility deployments, the Lorikeet will definitely not excel in zero-g environments, it's outclassed by more maneuverable specialty frames. But for deployments to planetary surfaces, the frame offers a more affordable (although less durable) alternative to the Varuna (flic.kr/s/aHsm89p5MW) the a more extensible (and repairable) alternative to the Krivlyaka (flic.kr/s/aHsm4d6e2v).
From a design perspective, the frame takes a ton of inspiration from both Malcolm Craig's MgN-333 (flic.kr/p/dEFocc) and Aardvark17's Budgie (flic.kr/p/2kgyyua) frames as well as my version of the HR-13 flic.kr/s/aHsmMLcB3m.
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Built for Mobile Frame Zero - a tabletop wargame.
Mobile Frame Hangar Nova (MFZ Community Forums).
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Pelecanus occidentalis, Pelícano, Brown Pelican (Rc: Residente Comun)
El Pelecanus occidentalis, comúnmente conocido como el Pelícano Pardo o Pelícano Café, es un ave marina costera grande y de color oscuro, caracterizada por un pico sobredimensionado y una distintiva bolsa gular (garganta) extensible. Es la única especie de pelícano que caza zambulléndose en picada desde el aire hacia el agua.
Características Físicas
Tamaño: Generalmente miden entre 1 y 1.37 metros (3 a 4.5 pies) de largo, con una envergadura alar de alrededor de 2 metros (6.5 pies) o más.
Plumaje: Los adultos son típicamente de color marrón grisáceo con el vientre negruzco, la cabeza blanca y un tono amarillo pálido en la corona. Durante la temporada de cría, la parte posterior y los lados del cuello adquieren un color marrón rojizo oscuro o castaño intenso.
Pico y Bolsa: Tienen un pico largo y gris con una gran bolsa de piel desnuda. Esta bolsa se utiliza como una red para recoger peces y agua, pudiendo retener hasta 11 litros (3 galones) de agua, varias veces más que su estómago.
Juveniles: Los pelícanos jóvenes son completamente marrones con el vientre blanco o pálido durante sus primeros años, hasta que adquieren el plumaje de adulto.
Hábitat y Comportamiento
Hábitat: Se encuentran durante todo el año en ambientes marinos y estuarinos a lo largo de las costas atlántica, pacífica y del Golfo de las Américas, desde la Columbia Británica y Nueva Escocia (fuera de la temporada de cría) hasta el norte de Chile y Venezuela. Se posan en elementos costeros como playas de arena, lagunas, espigones, muelles e islas pequeñas y aisladas para evitar depredadores terrestres.
Alimentación: Son expertos buceadores en picada, localizando cardúmenes de peces pequeños (como lacha, arenque y anchoas) desde hasta 21 metros (70 pies) en el aire antes de zambullirse de cabeza para aturdir y recoger a su presa. Luego drenan el agua de su bolsa antes de tragar el pescado.
Estructura Social: Son aves muy gregarias, viven en grandes bandadas durante todo el año y anidan en colonias, a menudo en islas.
Vuelo: En vuelo, son elegantes, generalmente volando en formaciones en V o en líneas únicas justo por encima de la superficie del agua, con el cuello recogido hacia atrás sobre los hombros.
El Pelícano Pardo es el ave nacional de varias naciones caribeñas y el ave estatal de Luisiana. Su población se ha recuperado en gran medida de una grave disminución a mediados del siglo XX causada por el pesticida DDT.
============ENGLISH======
The Pelecanus occidentalis, commonly known as the Brown Pelican, is a large, dark-colored coastal seabird with an oversized bill and a distinctive, extensible gular (throat) pouch. It is the only pelican species that hunts by plunge-diving from the air into the water.
Physical Characteristics
Size: They typically measure about 1 to 1.37 meters (3 to 4.5 feet) in length, with a wingspan of around 2 meters (6.5 feet) or more.
Plumage: Adults are generally grayish-brown with a blackish belly, a white head, and a pale yellow wash on the crown. During the breeding season, the back and sides of their neck turn a rich, dark reddish-brown or chestnut.
Bill and Pouch: They have a long, gray bill with a large, bare skin pouch. This pouch is used like a net to scoop up fish and water, holding up to 11 liters (3 gallons) of water, several times more than its stomach.
Juveniles: Young pelicans are entirely brown with a white or pale belly for their first few years until they acquire adult plumage.
Habitat and Behavior
Habitat: Brown pelicans are found year-round in marine and estuarine environments along the Atlantic, Pacific, and Gulf coasts of the Americas, from British Columbia and Nova Scotia in the non-breeding season down to northern Chile and Venezuela. They roost on coastal features such as sandy beaches, lagoons, jetties, piers, and small, isolated islands to avoid land predators.
Feeding: They are expert plunge-divers, spotting schools of small fish (such as menhaden, herring, and anchovies) from up to 21 meters (70 feet) in the air before diving headfirst to stun and scoop up their prey. They then drain the water from their pouch before swallowing the fish.
Social Structure: They are highly gregarious birds, living in large flocks year-round and nesting in colonies, often on islands.
Flight: In flight, they are graceful, typically flying in V-formations or single lines just above the water's surface, with their necks tucked back on their shoulders.
The Brown Pelican is the national bird of several Caribbean nations and the state bird of Louisiana. Its population has largely recovered from a severe decline in the mid-20th century caused by the pesticide DDT.
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Lugar de Observacion / Taken: Minas de sal, Bahia de las calderas, peravia, Republica Dominicana.
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Clase:Aves
Orden:Pelecaniformes
Familia:Pelecanidae
Género:Pelecanus
Especie:P. occidentalis
PHILIPPINE SEA (Sep. 26, 2021) Sailors guide an 11-meter rigid hull inflatable boat during a twin boom extensible crane training evolution in the mission bay aboard Independence-variant littoral combat ship USS Charleston (LCS 18). Charleston, part of Destroyer Squadron 7, is on a rotational deployment, operating in the U.S. 7th Fleet to enhance interoperability with partners and serve as a ready-response force in support of free and open Indo-Pacific region. (U.S. Navy photo by Mass Communication Specialist 2nd Class Ryan M. Breeden)
La Plaubel Makina II és una càmara de gran format de meitat del s. XX, extensible i destinada sobretot a la premsa. Feia servir plaques de 6,5x9cm però s'adapta sense problemes a porta-rodets de format 120, com en el cas d'aquesta.
Les primeres Makina no tenien telèmetre, però a partir de la Makina II del 1933 ja incorpora un. Posteriorment es refinarà el model amb la Makina IIS, que facilita molt el canvi de lents, i ja després de la guerra mundial, l'ultim model és la Makina III, amb molts canvis sobretot per a disparar flaix.
De fet, aquesta que tinc és una mica inusual ja que no sembla pas una Makina IIS per tal i com està montada la lent. De fet té dues parts, amb el obturador al mig, el que fa més dificil desmontar-la. Però en canvi té les dues finestretes del telèmetre rectangulars, el que és un element distintiu de les IIS. Probablement sigui una II a la que es va reformar el telèmetre per alguna raó, o bé es tracti d'un model just de transició. El que si no milloraren fou una refotuda manera d'agafar-la. Ergonomía? no en tenien ni idea!!
En tot cas és clàrament anterior a la guerra (ja que està marcada amb el DRP "Deutsches Reich Patent" en comptes del DBP de postguerra, "Deutsches BundesPatent". Crec que fou fabricada entre el 1933 i el 1936, més aviat cap al final del periode, ja que el frontal és cromat, i inicialment es produia en negre. Potser fou una de les darreres Makina II (abans del canvi al model IIS) i per això 1936 sembla la data més probable de producció.
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The Plaubel Makina II is a large format press camera from the 30's to 50's, strut-folding. It used 6.5x9cm glass plates but also 120 format backs, as this one.
The first Makina had no rangefinder, but in 1933 the Makina II already incorporates one. Later, the model will be refined with the Makina II S, which greatly facilitates the change of lens, and even after the World War, the latest model is the Makina III, with many refinements, especially for flash synchro. What they didn't get at all was an easy way to hold it. Ergonomics, what's that??
In fact, this one that I have is a little unusual since it does not look like a Makina IIS as the lens has two parts, with the shutter in the middle, which makes it more difficult to disassemble it. But otherwise it has rangefinder rectangular windows, which is a distinctive element of the IIS. It is probably a II to which the rangefinder was reformed for some reason, or it was just a transition model.
In any case, it was clearly made before WW2 (since it is marked with the DRP "Deutsches Reich Patent" instead of the post-war DBP, "Deutsches BundesPatent.") I think it was manufactured between 1933 and 1936, rather towards the end of this period, since the front is chromed, and initially it was produced in black. Perhaps it was one of the last Makina II (before the change to the IIS model) and for that reason 1936 seems the most probable date of production.
lommen9.home.xs4all.nl/plaubel/index.html
www.earlyphotography.co.uk/site/entry_C25.html
camera-wiki.org/wiki/Plaubel_Makina#The_6.5.C3.979_rangef...
PHILIPPINE SEA (Sep. 26, 2021) Sailors guide an 11-meter rigid hull inflatable boat during a twin boom extensible crane training evolution in the mission bay aboard Independence-variant littoral combat ship USS Charleston (LCS 18). Charleston, part of Destroyer Squadron 7, is on a rotational deployment, operating in the U.S. 7th Fleet to enhance interoperability with partners and serve as a ready-response force in support of free and open Indo-Pacific region. (U.S. Navy photo by Mass Communication Specialist 2nd Class Ryan M. Breeden)
" !::SSU::! Oriental Custom Horn ” is NEW CUSTOM HORN SYSTEM.
If you use BASE HORN and CUSTOM PARTS,
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---------Base kit---------
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2. [SIDE] Horn
3. [BACK] Horn
4. Color change HUD for Horn
5. first [Custom Parts] for [FRONT]
6. first [Custom Parts] for [SIDE]
7. first [Custom Parts] for [BACK]
-----------------------------
Custom parts are released from 2 stores.
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marketplace.secondlife.com/stores/197251
:: Round 9 ::
marketplace.secondlife.com/stores/190599
And the store may increase in future.
***If you are interested in this product development. please send IM to "umechiyo".
Do you know what I am ??? Commerson's frogfish grows up to 38 cm (15 in). Like other members of its family, it has a globular, extensible body. The soft skin is covered with small dermal spinules. Its skin is partially covered with a few small, wartlike protuberances, some variably shaped, scab-like blotches, and a few, small eye spots (ocelli) reminiscent of the holes in sponges. Its large mouth is prognathous, allowing it to consume prey as large as itself. Their coloration is extremely variable, as they tend to match their environments. Frogfish can change their coloration in a few weeks. However, the dominant coloration goes from grey to black, passing through a whole range of related hues, such as cream, pink, yellow, red, and brown, and also usually with circular eye spots or blotches that are darker than the background. Nuweiba, Gulf of Aqaba, Egypt.
60x24 boxpleat
Papier kraft
L'idée derrière ce modèle était d'utiliser les intersections comme points pivots, possible grâce aux coupes, de manière à obtenir un mécanisme actionnable. Au départ, je voulais ajouter un gant de boxe au bout, le genre qu'on voit parfois dans les dessins animés. Je suis passé à une pince simple car l'obtention du mouvement de translation du gant suite au mouvement de rotation du mécanisme m'était trop problématique. Effectivement, on peut «actionner» ce modèle, mais en appuyant sur les intersections et en les étirant. Le papier kraft utilisé (pour la couleur) n'est pas d'assez bonne qualité pour valider le fonctionnement du mécanisme.
The idea behind this model was to use the intersections as pivot points, possible with cuts, to obtain an actionable mechanism. In the beginning, I wanted to add a boxing glove at the tip, the kind that sometimes appear in cartoons. I moved to a grabber since getting the translation movement from the rotation movement of the mecanism proved too problematic. Indeed, you can «actuate» the model by holding the intersections and stretching them. The quality of the kraft paper used (for the color) was not good enough to validate if the mechanism works or not.
EXPLORE 25/05/2012
Un pélican du zoo de Pessac (Gironde)
Les pélicans sont de grands oiseaux (de 105 à 188 cm) aquatiques piscivores caractérisés par un grand bec muni d'une volumineuse poche extensible.
Pelicans are large water birds in the family Pelecanidae. They are characterised by a long beak and large throat pouch, used in catching, and draining water from, their prey.
A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος anisos, "unequal" and πτερόν pteron, "wing", because the hindwing is broader than the forewing). Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Dragonflies can be mistaken for the related group, damselflies (Zygoptera), which are similar in structure, though usually lighter in build; however, the wings of most dragonflies are held flat and away from the body, while damselflies hold their wings folded at rest, along or above the abdomen. Dragonflies are agile fliers, while damselflies have a weaker, fluttery flight. Many dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. An adult dragonfly's compound eyes have nearly 24,000 ommatidia each.
Fossils of very large dragonfly-like insects, sometimes called griffinflies, are found from 325 million years ago (Mya) in Upper Carboniferous rocks; these had wingspans up to about 750 mm (30 in), but were only distant ancestors, not true dragonflies. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threatens dragonfly populations around the world.
Dragonflies are predators, both in their aquatic nymphs stage (also known as naiads) and as adults. In some species, the nymphal stage lasts for up to five years, and the adult stage may be as long as ten weeks, but most species have an adult lifespan in the order of five weeks or less, and some survive for only a few days. They are fast, agile fliers, sometimes migrating across oceans, and often live near water. They have a uniquely complex mode of reproduction involving indirect insemination, delayed fertilization, and sperm competition. During mating, the male grasps the female at the back of the head, and the female curls her abdomen under her body to pick up sperm from the male's secondary genitalia at the front of his abdomen, forming the "heart" or "wheel" posture.
Dragonflies are represented in human culture on artefacts such as pottery, rock paintings, statues and Art Nouveau jewellery. They are used in traditional medicine in Japan and China, and caught for food in Indonesia. They are symbols of courage, strength, and happiness in Japan, but seen as sinister in European folklore. Their bright colours and agile flight are admired in the poetry of Lord Tennyson and the prose of H. E. Bates.
Evolution
Dragonflies and their relatives are similar in structure to an ancient group, meganisoptera, from the 325 Mya Upper Carboniferous of Europe, a group that included the largest insect that ever lived, Meganeuropsis permiana from the Early Permian, with a wingspan around 750 mm (30 in);. Known informally as "griffinflies", their fossil record ends with the Permian–Triassic extinction event (about 247 Mya). The Protanisoptera, another ancestral group that lacks certain wing vein characters found in modern Odonata, lived from the Early to Late Permian age until the end Permian event, and are known from fossil wings from current-day United States, Russia, and Australia, suggesting they might have been cosmopolitan in distribution. While both of those groups are sometimes referred to as "giant dragonflies", in fact true dragonflies/odonata are more modern insects that had not evolved yet.
Modern dragonflies do retain some traits of their distant predecessors, and are in a group known as palaeoptera, ancient-winged. They, like the gigantic pre-dinosaur griffinflies, lack the ability to fold their wings up against their bodies in the way modern insects do, although some evolved their own different way to do so. The forerunners of modern Odonata are included in a clade called the Panodonata, which include the basal Zygoptera (damselflies) and the Anisoptera (true dragonflies). Today, some 3,000 species are extant around the world.
The relationships of anisopteran families are not fully resolved as of 2013, but all the families are monophyletic except the Corduliidae; the Gomphidae are a sister taxon to all other Anisoptera, the Austropetaliidae are sister to the Aeshnoidea, and the Chlorogomphidae are sister to a clade that includes the Synthemistidae and Libellulidae. On the cladogram, dashed lines indicate unresolved relationships; English names are given (in parentheses)
Distribution and diversity
About 3,012 species of dragonflies were known in 2010; these are classified into 348 genera in 11 families. The distribution of diversity within the biogeographical regions are summarized below (the world numbers are not ordinary totals, as overlaps in species occur).
Dragonflies live on every continent except Antarctica. In contrast to the damselflies (Zygoptera), which tend to have restricted distributions, some genera and species are spread across continents. For example, the blue-eyed darner Rhionaeschna multicolor lives all across North America, and in Central America; emperors Anax live throughout the Americas from as far north as Newfoundland to as far south as Bahia Blanca in Argentina, across Europe to central Asia, North Africa, and the Middle East. The globe skimmer Pantala flavescens is probably the most widespread dragonfly species in the world; it is cosmopolitan, occurring on all continents in the warmer regions. Most Anisoptera species are tropical, with far fewer species in temperate regions.
Some dragonflies, including libellulids and aeshnids, live in desert pools, for example in the Mojave Desert, where they are active in shade temperatures between 18 and 45 °C (64.4 to 113 °F); these insects were able to survive body temperatures above the thermal death point of insects of the same species in cooler places.
Dragonflies live from sea level up to the mountains, decreasing in species diversity with altitude. Their altitudinal limit is about 3700 m, represented by a species of Aeshna in the Pamirs.
Dragonflies become scarce at higher latitudes. They are not native to Iceland, but individuals are occasionally swept in by strong winds, including a Hemianax ephippiger native to North Africa, and an unidentified darter species. In Kamchatka, only a few species of dragonfly including the treeline emerald Somatochlora arctica and some aeshnids such as Aeshna subarctica are found, possibly because of the low temperature of the lakes there. The treeline emerald also lives in northern Alaska, within the Arctic Circle, making it the most northerly of all dragonflies.
General description
Dragonflies (suborder Anisoptera) are heavy-bodied, strong-flying insects that hold their wings horizontally both in flight and at rest. By contrast, damselflies (suborder Zygoptera) have slender bodies and fly more weakly; most species fold their wings over the abdomen when stationary, and the eyes are well separated on the sides of the head.
An adult dragonfly has three distinct segments, the head, thorax, and abdomen, as in all insects. It has a chitinous exoskeleton of hard plates held together with flexible membranes. The head is large with very short antennae. It is dominated by the two compound eyes, which cover most of its surface. The compound eyes are made up of ommatidia, the numbers being greater in the larger species. Aeshna interrupta has 22650 ommatidia of two varying sizes, 4500 being large. The facets facing downward tend to be smaller. Petalura gigantea has 23890 ommatidia of just one size. These facets provide complete vision in the frontal hemisphere of the dragonfly. The compound eyes meet at the top of the head (except in the Petaluridae and Gomphidae, as also in the genus Epiophlebia). Also, they have three simple eyes or ocelli. The mouthparts are adapted for biting with a toothed jaw; the flap-like labrum, at the front of the mouth, can be shot rapidly forward to catch prey. The head has a system for locking it in place that consists of muscles and small hairs on the back of the head that grip structures on the front of the first thoracic segment. This arrester system is unique to the Odonata, and is activated when feeding and during tandem flight.
The thorax consists of three segments as in all insects. The prothorax is small and is flattened dorsally into a shield-like disc, which has two transverse ridges. The mesothorax and metathorax are fused into a rigid, box-like structure with internal bracing, and provide a robust attachment for the powerful wing muscles inside. The thorax bears two pairs of wings and three pairs of legs. The wings are long, veined, and membranous, narrower at the tip and wider at the base. The hindwings are broader than the forewings and the venation is different at the base. The veins carry haemolymph, which is analogous to blood in vertebrates, and carries out many similar functions, but which also serves a hydraulic function to expand the body between nymphal stages (instars) and to expand and stiffen the wings after the adult emerges from the final nymphal stage. The leading edge of each wing has a node where other veins join the marginal vein, and the wing is able to flex at this point. In most large species of dragonflies, the wings of females are shorter and broader than those of males. The legs are rarely used for walking, but are used to catch and hold prey, for perching, and for climbing on plants. Each has two short basal joints, two long joints, and a three-jointed foot, armed with a pair of claws. The long leg joints bear rows of spines, and in males, one row of spines on each front leg is modified to form an "eyebrush", for cleaning the surface of the compound eye.
The abdomen is long and slender and consists of 10 segments. Three terminal appendages are on segment 10; a pair of superiors (claspers) and an inferior. The second and third segments are enlarged, and in males, on the underside of the second segment has a cleft, forming the secondary genitalia consisting of the lamina, hamule, genital lobe, and penis. There are remarkable variations in the presence and the form of the penis and the related structures, the flagellum, cornua, and genital lobes. Sperm is produced at the 9th segment, and is transferred to the secondary genitalia prior to mating. The male holds the female behind the head using a pair of claspers on the terminal segment. In females, the genital opening is on the underside of the eighth segment, and is covered by a simple flap (vulvar lamina) or an ovipositor, depending on species and the method of egg-laying. Dragonflies having simple flaps shed the eggs in water, mostly in flight. Dragonflies having ovipositors use them to puncture soft tissues of plants and place the eggs singly in each puncture they make.
Dragonfly nymphs vary in form with species, and are loosely classed into claspers, sprawlers, hiders, and burrowers. The first instar is known as a prolarva, a relatively inactive stage from which it quickly moults into the more active nymphal form. The general body plan is similar to that of an adult, but the nymph lacks wings and reproductive organs. The lower jaw has a huge, extensible labium, armed with hooks and spines, which is used for catching prey. This labium is folded under the body at rest and struck out at great speed by hydraulic pressure created by the abdominal muscles. Whereas damselfly nymphs have three feathery external gills, dragonfly nymphs have internal gills, located around the fourth and fifth abdominal segments. Water is pumped in and out of the abdomen through an opening at the tip. The naiads of some clubtails (Gomphidae) that burrow into the sediment, have a snorkel-like tube at the end of the abdomen enabling them to draw in clean water while they are buried in mud. Naiads can forcefully expel a jet of water to propel themselves with great rapidity.
Colouration
Many adult dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. Their overall colouration is often a combination of yellow, red, brown, and black pigments, with structural colours. Blues are typically created by microstructures in the cuticle that reflect blue light. Greens often combine a structural blue with a yellow pigment. Freshly emerged adults, known as tenerals, are often pale-coloured and obtain their typical colours after a few days, some have their bodies covered with a pale blue, waxy powderiness called pruinosity; it wears off when scraped during mating, leaving darker areas.
Some dragonflies, such as the green darner, Anax junius, have a noniridescent blue that is produced structurally by scatter from arrays of tiny spheres in the endoplasmic reticulum of epidermal cells underneath the cuticle.
The wings of dragonflies are generally clear, apart from the dark veins and pterostigmata. In the chasers (Libellulidae), however, many genera have areas of colour on the wings: for example, groundlings (Brachythemis) have brown bands on all four wings, while some scarlets (Crocothemis) and dropwings (Trithemis) have bright orange patches at the wing bases. Some aeshnids such as the brown hawker (Aeshna grandis) have translucent, pale yellow wings.
Dragonfly nymphs are usually a well-camouflaged blend of dull brown, green, and grey.
Biology
Ecology
Dragonflies and damselflies are predatory both in the aquatic nymphal and adult stages. Nymphs feed on a range of freshwater invertebrates and larger ones can prey on tadpoles and small fish. Adults capture insect prey in the air, making use of their acute vision and highly controlled flight. The mating system of dragonflies is complex, and they are among the few insect groups that have a system of indirect sperm transfer along with sperm storage, delayed fertilization, and sperm competition.
Adult males vigorously defend territories near water; these areas provide suitable habitat for the nymphs to develop, and for females to lay their eggs. Swarms of feeding adults aggregate to prey on swarming prey such as emerging flying ants or termites.
Dragonflies as a group occupy a considerable variety of habitats, but many species, and some families, have their own specific environmental requirements. Some species prefer flowing waters, while others prefer standing water. For example, the Gomphidae (clubtails) live in running water, and the Libellulidae (skimmers) live in still water. Some species live in temporary water pools and are capable of tolerating changes in water level, desiccation, and the resulting variations in temperature, but some genera such as Sympetrum (darters) have eggs and nymphs that can resist drought and are stimulated to grow rapidly in warm, shallow pools, also often benefiting from the absence of predators there. Vegetation and its characteristics including submerged, floating, emergent, or waterside are also important. Adults may require emergent or waterside plants to use as perches; others may need specific submerged or floating plants on which to lay eggs. Requirements may be highly specific, as in Aeshna viridis (green hawker), which lives in swamps with the water-soldier, Stratiotes aloides. The chemistry of the water, including its trophic status (degree of enrichment with nutrients) and pH can also affect its use by dragonflies. Most species need moderate conditions, not too eutrophic, not too acidic; a few species such as Sympetrum danae (black darter) and Libellula quadrimaculata (four-spotted chaser) prefer acidic waters such as peat bogs, while others such as Libellula fulva (scarce chaser) need slow-moving, eutrophic waters with reeds or similar waterside plants.
Behaviour
Many dragonflies, particularly males, are territorial. Some defend a territory against others of their own species, some against other species of dragonfly and a few against insects in unrelated groups. A particular perch may give a dragonfly a good view over an insect-rich feeding ground; males of many species such as the Pachydiplax longipennis (blue dasher) jostle other dragonflies to maintain the right to alight there. Defending a breeding territory is common among male dragonflies, especially in species that congregate around ponds. The territory contains desirable features such as a sunlit stretch of shallow water, a special plant species, or the preferred substrate for egg-laying. The territory may be small or large, depending on its quality, the time of day, and the number of competitors, and may be held for a few minutes or several hours. Dragonflies including Tramea lacerata (black saddlebags) may notice landmarks that assist in defining the boundaries of the territory. Landmarks may reduce the costs of territory establishment, or might serve as a spatial reference. Some dragonflies signal ownership with striking colours on the face, abdomen, legs, or wings. The Plathemis lydia (common whitetail) dashes towards an intruder holding its white abdomen aloft like a flag. Other dragonflies engage in aerial dogfights or high-speed chases. A female must mate with the territory holder before laying her eggs. There is also conflict between the males and females. Females may sometimes be harassed by males to the extent that it affects their normal activities including foraging and in some dimorphic species females have evolved multiple forms with some forms appearing deceptively like males. In some species females have evolved behavioural responses such as feigning death to escape the attention of males. Similarly, selection of habitat by adult dragonflies is not random, and terrestrial habitat patches may be held for up to 3 months. A species tightly linked to its birth site utilises a foraging area that is several orders of magnitude larger than the birth site.
Reproduction
Mating in dragonflies is a complex, precisely choreographed process. First, the male has to attract a female to his territory, continually driving off rival males. When he is ready to mate, he transfers a packet of sperm from his primary genital opening on segment 9, near the end of his abdomen, to his secondary genitalia on segments 2–3, near the base of his abdomen. The male then grasps the female by the head with the claspers at the end of his abdomen; the structure of the claspers varies between species, and may help to prevent interspecific mating. The pair flies in tandem with the male in front, typically perching on a twig or plant stem. The female then curls her abdomen downwards and forwards under her body to pick up the sperm from the male's secondary genitalia, while the male uses his "tail" claspers to grip the female behind the head: this distinctive posture is called the "heart" or "wheel"; the pair may also be described as being "in cop".
Egg-laying (ovipositing) involves not only the female darting over floating or waterside vegetation to deposit eggs on a suitable substrate, but also the male hovering above her or continuing to clasp her and flying in tandem. The male attempts to prevent rivals from removing his sperm and inserting their own, something made possible by delayed fertilisation and driven by sexual selection. If successful, a rival male uses his penis to compress or scrape out the sperm inserted previously; this activity takes up much of the time that a copulating pair remains in the heart posture. Flying in tandem has the advantage that less effort is needed by the female for flight and more can be expended on egg-laying, and when the female submerges to deposit eggs, the male may help to pull her out of the water.
Egg-laying takes two different forms depending on the species. The female in some families has a sharp-edged ovipositor with which she slits open a stem or leaf of a plant on or near the water, so she can push her eggs inside. In other families such as clubtails (Gomphidae), cruisers (Macromiidae), emeralds (Corduliidae), and skimmers (Libellulidae), the female lays eggs by tapping the surface of the water repeatedly with her abdomen, by shaking the eggs out of her abdomen as she flies along, or by placing the eggs on vegetation. In a few species, the eggs are laid on emergent plants above the water, and development is delayed until these have withered and become immersed.
Life cycle
Dragonflies are hemimetabolous insects; they do not have a pupal stage and undergo an incomplete metamorphosis with a series of nymphal stages from which the adult emerges. Eggs laid inside plant tissues are usually shaped like grains of rice, while other eggs are the size of a pinhead, ellipsoidal, or nearly spherical. A clutch may have as many as 1500 eggs, and they take about a week to hatch into aquatic nymphs or naiads which moult between six and 15 times (depending on species) as they grow. Most of a dragonfly's life is spent as a nymph, beneath the water's surface. The nymph extends its hinged labium (a toothed mouthpart similar to a lower mandible, which is sometimes termed as a "mask" as it is normally folded and held before the face) that can extend forward and retract rapidly to capture prey such as mosquito larvae, tadpoles, and small fish. They breathe through gills in their rectum, and can rapidly propel themselves by suddenly expelling water through the anus. Some naiads, such as the later stages of Antipodophlebia asthenes, hunt on land.
The nymph stage of dragonflies lasts up to five years in large species, and between two months and three years in smaller species. When the naiad is ready to metamorphose into an adult, it stops feeding and makes its way to the surface, generally at night. It remains stationary with its head out of the water, while its respiration system adapts to breathing air, then climbs up a reed or other emergent plant, and moults (ecdysis). Anchoring itself firmly in a vertical position with its claws, its skin begins to split at a weak spot behind the head. The adult dragonfly crawls out of its nymph skin, the exuvia, arching backwards when all but the tip of its abdomen is free, to allow its exoskeleton to harden. Curling back upwards, it completes its emergence, swallowing air, which plumps out its body, and pumping haemolymph into its wings, which causes them to expand to their full extent.
Dragonflies in temperate areas can be categorized into two groups, an early group and a later one. In any one area, individuals of a particular "spring species" emerge within a few days of each other. The springtime darner (Basiaeschna janata), for example, is suddenly very common in the spring, but disappears a few weeks later and is not seen again until the following year. By contrast, a "summer species" emerges over a period of weeks or months, later in the year. They may be seen on the wing for several months, but this may represent a whole series of individuals, with new adults hatching out as earlier ones complete their lifespans.
Sex ratios
The sex ratio of male to female dragonflies varies both temporally and spatially. Adult dragonflies have a high male-biased ratio at breeding habitats. The male-bias ratio has contributed partially to the females using different habitats to avoid male harassment. As seen in Hine's emerald dragonfly (Somatochlora hineana), male populations use wetland habitats, while females use dry meadows and marginal breeding habitats, only migrating to the wetlands to lay their eggs or to find mating partners. Unwanted mating is energetically costly for females because it affects the amount of time that they are able to spend foraging.
Flight
Dragonflies are powerful and agile fliers, capable of migrating across the sea, moving in any direction, and changing direction suddenly. In flight, the adult dragonfly can propel itself in six directions: upward, downward, forward, backward, to left and to right. They have four different styles of flight: A number of flying modes are used that include counter-stroking, with forewings beating 180° out of phase with the hindwings, is used for hovering and slow flight. This style is efficient and generates a large amount of lift; phased-stroking, with the hindwings beating 90° ahead of the forewings, is used for fast flight. This style creates more thrust, but less lift than counter-stroking; synchronised-stroking, with forewings and hindwings beating together, is used when changing direction rapidly, as it maximises thrust; and gliding, with the wings held out, is used in three situations: free gliding, for a few seconds in between bursts of powered flight; gliding in the updraft at the crest of a hill, effectively hovering by falling at the same speed as the updraft; and in certain dragonflies such as darters, when "in cop" with a male, the female sometimes simply glides while the male pulls the pair along by beating his wings.
The wings are powered directly, unlike most families of insects, with the flight muscles attached to the wing bases. Dragonflies have a high power/weight ratio, and have been documented accelerating at 4 G linearly and 9 G in sharp turns while pursuing prey.
Dragonflies generate lift in at least four ways at different times, including classical lift like an aircraft wing; supercritical lift with the wing above the critical angle, generating high lift and using very short strokes to avoid stalling; and creating and shedding vortices. Some families appear to use special mechanisms, as for example the Libellulidae which take off rapidly, their wings beginning pointed far forward and twisted almost vertically. Dragonfly wings behave highly dynamically during flight, flexing and twisting during each beat. Among the variables are wing curvature, length and speed of stroke, angle of attack, forward/back position of wing, and phase relative to the other wings.
Flight speed
Old and unreliable claims are made that dragonflies such as the southern giant darner can fly up to 97 km/h (60 mph). However, the greatest reliable flight speed records are for other types of insects. In general, large dragonflies like the hawkers have a maximum speed of 36–54 km/h (22–34 mph) with average cruising speed of about 16 km/h (9.9 mph). Dragonflies can travel at 100 body-lengths per second in forward flight, and three lengths per second backwards.
Motion camouflage
n high-speed territorial battles between male Australian emperors (Hemianax papuensis), the fighting dragonflies adjust their flight paths to appear stationary to their rivals, minimizing the chance of being detected as they approach.[a] To achieve the effect, the attacking dragonfly flies towards his rival, choosing his path to remain on a line between the rival and the start of his attack path. The attacker thus looms larger as he closes on the rival, but does not otherwise appear to move. Researchers found that six of 15 encounters involved motion camouflage.
Temperature control
The flight muscles need to be kept at a suitable temperature for the dragonfly to be able to fly. Being cold-blooded, they can raise their temperature by basking in the sun. Early in the morning, they may choose to perch in a vertical position with the wings outstretched, while in the middle of the day, a horizontal stance may be chosen. Another method of warming up used by some larger dragonflies is wing-whirring, a rapid vibration of the wings that causes heat to be generated in the flight muscles. The green darner (Anax junius) is known for its long-distance migrations, and often resorts to wing-whirring before dawn to enable it to make an early start.
Becoming too hot is another hazard, and a sunny or shady position for perching can be selected according to the ambient temperature. Some species have dark patches on the wings which can provide shade for the body, and a few use the obelisk posture to avoid overheating. This behaviour involves doing a "handstand", perching with the body raised and the abdomen pointing towards the sun, thus minimising the amount of solar radiation received. On a hot day, dragonflies sometimes adjust their body temperature by skimming over a water surface and briefly touching it, often three times in quick succession. This may also help to avoid desiccation.
Feeding
Adult dragonflies hunt on the wing using their exceptionally acute eyesight and strong, agile flight. They are almost exclusively carnivorous, eating a wide variety of insects ranging from small midges and mosquitoes to butterflies, moths, damselflies, and smaller dragonflies. A large prey item is subdued by being bitten on the head and is carried by the legs to a perch. Here, the wings are discarded and the prey usually ingested head first. A dragonfly may consume as much as a fifth of its body weight in prey per day. Dragonflies are also some of the insect world's most efficient hunters, catching up to 95% of the prey they pursue.
The nymphs are voracious predators, eating most living things that are smaller than they are. Their staple diet is mostly bloodworms and other insect larvae, but they also feed on tadpoles and small fish. A few species, especially those that live in temporary waters, are likely to leave the water to feed. Nymphs of Cordulegaster bidentata sometimes hunt small arthropods on the ground at night, while some species in the Anax genus have even been observed leaping out of the water to attack and kill full-grown tree frogs.
Eyesight
Dragonfly vision is thought to be like slow motion for humans. Dragonflies see faster than we do; they see around 200 images per second. A dragonfly can see in 360 degrees, and nearly 80 percent of the insect's brain is dedicated to its sight.
Predators
Although dragonflies are swift and agile fliers, some predators are fast enough to catch them. These include falcons such as the American kestrel, the merlin, and the hobby; nighthawks, swifts, flycatchers and swallows also take some adults; some species of wasps, too, prey on dragonflies, using them to provision their nests, laying an egg on each captured insect. In the water, various species of ducks and herons eat dragonfly nymphs and they are also preyed on by newts, frogs, fish, and water spiders. Amur falcons, which migrate over the Indian Ocean at a period that coincides with the migration of the globe skimmer dragonfly, Pantala flavescens, may actually be feeding on them while on the wing.
Parasites
Dragonflies are affected by three major groups of parasites: water mites, gregarine protozoa, and trematode flatworms (flukes). Water mites, Hydracarina, can kill smaller dragonfly nymphs, and may also be seen on adults. Gregarines infect the gut and may cause blockage and secondary infection. Trematodes are parasites of vertebrates such as frogs, with complex life cycles often involving a period as a stage called a cercaria in a secondary host, a snail. Dragonfly nymphs may swallow cercariae, or these may tunnel through a nymph's body wall; they then enter the gut and form a cyst or metacercaria, which remains in the nymph for the whole of its development. If the nymph is eaten by a frog, the amphibian becomes infected by the adult or fluke stage of the trematode.
Dragonflies and humans
Conservation
Most odonatologists live in temperate areas and the dragonflies of North America and Europe have been the subject of much research. However, the majority of species live in tropical areas and have been little studied. With the destruction of rainforest habitats, many of these species are in danger of becoming extinct before they have even been named. The greatest cause of decline is forest clearance with the consequent drying up of streams and pools which become clogged with silt. The damming of rivers for hydroelectric schemes and the drainage of low-lying land has reduced suitable habitat, as has pollution and the introduction of alien species.
In 1997, the International Union for Conservation of Nature set up a status survey and conservation action plan for dragonflies. This proposes the establishment of protected areas around the world and the management of these areas to provide suitable habitat for dragonflies. Outside these areas, encouragement should be given to modify forestry, agricultural, and industrial practices to enhance conservation. At the same time, more research into dragonflies needs to be done, consideration should be given to pollution control and the public should be educated about the importance of biodiversity.
Habitat degradation has reduced dragonfly populations across the world, for example in Japan. Over 60% of Japan's wetlands were lost in the 20th century, so its dragonflies now depend largely on rice fields, ponds, and creeks. Dragonflies feed on pest insects in rice, acting as a natural pest control. Dragonflies are steadily declining in Africa, and represent a conservation priority.
The dragonfly's long lifespan and low population density makes it vulnerable to disturbance, such as from collisions with vehicles on roads built near wetlands. Species that fly low and slow may be most at risk.
Dragonflies are attracted to shiny surfaces that produce polarization which they can mistake for water, and they have been known to aggregate close to polished gravestones, solar panels, automobiles, and other such structures on which they attempt to lay eggs. These can have a local impact on dragonfly populations; methods of reducing the attractiveness of structures such as solar panels are under experimentation.
In culture
A blue-glazed faience dragonfly amulet was found by Flinders Petrie at Lahun, from the Late Middle Kingdom of ancient Egypt.
Many Native American tribes consider dragonflies to be medicine animals that had special powers. For example, the southwestern tribes, including the Pueblo, Hopi, and Zuni, associated dragonflies with transformation. They referred to dragonflies as "snake doctors" because they believed dragonflies followed snakes into the ground and healed them if they were injured. For the Navajo, dragonflies symbolize pure water. Often stylized in a double-barred cross design, dragonflies are a common motif in Zuni pottery, as well as Hopi rock art and Pueblo necklaces.: 20–26
As a seasonal symbol in Japan, the dragonflies are associated with season of autumn. In Japan, they are symbols of rebirth, courage, strength, and happiness. They are also depicted frequently in Japanese art and literature, especially haiku poetry. Japanese children catch large dragonflies as a game, using a hair with a small pebble tied to each end, which they throw into the air. The dragonfly mistakes the pebbles for prey, gets tangled in the hair, and is dragged to the ground by the weight.: 38
In Chinese culture, dragonflies symbolize both change and instability. They are also symbols in the Chinese practices of Feng Shui, where placements of dragonfly statues and artwork in parts of a home or office are believed to bring new insights and positive changes.
In both China and Japan, dragonflies have been used in traditional medicine. In Indonesia, adult dragonflies are caught on poles made sticky with birdlime, then fried in oil as a delicacy.
Images of dragonflies are common in Art Nouveau, especially in jewellery designs. They have also been used as a decorative motif on fabrics and home furnishings. Douglas, a British motorcycle manufacturer based in Bristol, named its innovatively designed postwar 350-cc flat-twin model the Dragonfly.
Among the classical names of Japan are Akitsukuni (秋津国), Akitsushima (秋津島), Toyo-akitsushima (豊秋津島). Akitsu is an old word for dragonfly, so one interpretation of Akitsushima is "Dragonfly Island". This is attributed to a legend in which Japan's mythical founder, Emperor Jimmu, was bitten by a mosquito, which was then eaten by a dragonfly.
In Europe, dragonflies have often been seen as sinister. Some English vernacular names, such as "horse-stinger", "devil's darning needle", and "ear cutter", link them with evil or injury. Swedish folklore holds that the devil uses dragonflies to weigh people's souls.: 25–27 The Norwegian name for dragonflies is Øyenstikker ("eye-poker"), and in Portugal, they are sometimes called tira-olhos ("eyes-snatcher"). They are often associated with snakes, as in the Welsh name gwas-y-neidr, "adder's servant". The Southern United States terms "snake doctor" and "snake feeder" refer to a folk belief that dragonflies catch insects for snakes or follow snakes around and stitch them back together if they are injured. Interestingly, the Hungarian name for dragonfly is szitakötő ("sieve-knitter").
The watercolourist Moses Harris (1731–1785), known for his The Aurelian or natural history of English insects (1766), published in 1780, the first scientific descriptions of several Odonata including the banded demoiselle, Calopteryx splendens. He was the first English artist to make illustrations of dragonflies accurate enough to be identified to species (Aeshna grandis at top left of plate illustrated), though his rough drawing of a nymph (at lower left) with the mask extended appears to be plagiarised.[b]
More recently, dragonfly watching has become popular in America as some birdwatchers seek new groups to observe.
In heraldry, like other winged insects, the dragonfly is typically depicted tergiant (with its back facing the viewer), with its head to chief.
In poetry and literature
Lafcadio Hearn wrote in his 1901 book A Japanese Miscellany that Japanese poets had created dragonfly haiku "almost as numerous as are the dragonflies themselves in the early autumn." The poet Matsuo Bashō (1644–1694) wrote haiku such as "Crimson pepper pod / add two pairs of wings, and look / darting dragonfly", relating the autumn season to the dragonfly. Hori Bakusui (1718–1783) similarly wrote "Dyed he is with the / Colour of autumnal days, / O red dragonfly."
The poet Lord Tennyson, described a dragonfly splitting its old skin and emerging shining metallic blue like "sapphire mail" in his 1842 poem "The Two Voices", with the lines "An inner impulse rent the veil / Of his old husk: from head to tail / Came out clear plates of sapphire mail."
The novelist H. E. Bates described the rapid, agile flight of dragonflies in his 1937 nonfiction book Down the River:
I saw, once, an endless procession, just over an area of water-lilies, of small sapphire dragonflies, a continuous play of blue gauze over the snowy flowers above the sun-glassy water. It was all confined, in true dragonfly fashion, to one small space. It was a continuous turning and returning, an endless darting, poising, striking and hovering, so swift that it was often lost in sunlight.
In technology
A dragonfly has been genetically modified with light-sensitive "steering neurons" in its nerve cord to create a cyborg-like "DragonflEye". The neurons contain genes like those in the eye to make them sensitive to light. Miniature sensors, a computer chip and a solar panel were fitted in a "backpack" over the insect's thorax in front of its wings. Light is sent down flexible light-pipes named optrodes[c] from the backpack into the nerve cord to give steering commands to the insect. The result is a "micro-aerial vehicle that's smaller, lighter and stealthier than anything else that's manmade".
[Credit: en.wikipedia.org/]
To control Information Technology (IT) costs we think about and act within the enterprise as a whole, in part because we sell enterprise and mid-level solutions. We apply an Enterprise Architecture (EA) strategy which at the top level is comprised of infrastructure and communication considerations. This is not just about technical infrastructure, defined or designed by IT, because it is highly likely that such individual solutions (one offs) will not align to core business strategies (vertical needs verses horizontal needs spanning the whole company).
It is not really possible to do this, that is consider the entire company's needs, without significant participation by the business for which we use terms such as Solution Delivery or Product Management. Product and program managers from a solution delivery framework gather information, report back to the business, and return to apply the business strategies to align with short, medium, and especially long term business goals.
This business and implementation strategy focus is a change agent, to reduce siloed thinking, and achieve more horizontal capability across units. We reduce multiple applications, which take time to manage and maintain, and where it makes sense, fold them into one. Because we take security and privacy of our customers very seriously, any applications which may be at risk have been identified and are brought up into our standards. The process of combining risk management goals, application and data reduction streams saves money, although the process of so much change at once can be stressful at the unit, project, and personal levels.
We seek to empower self-service among our partners, customers and employees, for access to all kinds of information they need, and internally reduce redundant data stores, for example referring to customers by one identifier if possible. This is especially challenging in our partner relationships with multiple data stores that contain similar information about customers which are identified in completely different ways. This is the reason for serious data modeling and tight or loose coupling where needed – to retrieve and move information back to the partner systems. We leverage Microsoft software, and then buy, build, minimize or reuse existing systems.
In order to be more successful in our efforts to control IT costs we strive to increase flexibility among existing staff and provide rewards for strategic thinking – this strategic thinking aligns along company-wide goals. We need people with the right skills who work in efficient methods, only including the people who need to be included to make decisions or act. In fact we need to change confrontational and passive aggressive behaviors internally to collaborative personality styles – changing the organizations culture is doable but difficult. For more information I recommend reading "The Heart of Change" by Kotter and Cohen.
The technologies we invest in to help control IT costs are our own. We custom write stuff served up on Microsoft servers and plan to use SharePoint as the UI for our new change request tool. We are substantially reducing and eliminating the number of different applications (SQL stored procedures or XML Blobs mostly) we use and maintain on a daily basis. We are moving from C++ to C#/.NET (C Sharp and .Net technologies).
We use Microsoft software as our strategy to control IT costs - it is easy to manage, and has great support. Some team members keep an eye on relevant Open Source software as competitive analysis. When we use it, we know not only how but why.
Our company is getting the maximum value from its data center investment because we have not invested to the level we need for our infrastructure. We expect to remediate this lack of investment after deploying skilled, thoughtful product managers with the right combination of education and practical experience to assist in this effort through the next couple of years.
What is our organization doing to maximize the value from its data center investment? In addition to the other things mentioned we outsource development and support to India, Israel, and developing countries, etc. We also are making use of tax advantaged locations for large savings in transactions.
We are adding metrics and measurements by which we evaluate not just personal progress but internal and external customer satisfaction with our IT initiatives on a project by project basis to self-improve.
The practices which enable us to maximize value from our IT investment are varied and multifaceted. To maximize ongoing investment we are adding solution delivery strategies, planning ahead, and aligning IT with company-wide goals. Of course in our space we have some unique issues, and as a public company even more so. One thing that may surprise you is some of our projects we do end to end locally because of how critical success is. We leverage our best, most successful local managers to produce projects and design larger scale solutions if we determine it is the best strategy – so in this way we are flexible – we don't just out source everything.
We are in the process of reducing the number of applications we need to maintain, and where it is appropriate fold one into another so long as the user interface or back ends do not become unmanageable. We are making over our change request platform from top to bottom which we feel will enable quicker turnarounds on change requests – it is both loosely and tightly coupled where it needs to be. For the presentation layer we choose Microsoft SharePoint.
Conversely, what factors are inhibiting our organization from reaping the maximum value from its data center investments? The factors inhibiting the maximum value include a lack of foresight in strategic planning for long term goals –
1. Putting temporary things together to just meet immediate needs.
2. Focusing on small details and not seeing the big picture.
3. Lack of metrics to evaluate progress, process, and client / customer / partner success.
4. Unwillingness of team members to change or promote change even when it is in their and the companies' best interest.
5. Having too many data centers, identifying customers in too many ways.
How important is productivity within the IT function in our efforts to control IT costs and maximize our data center investment? Functionality, capacity, and reliability far outstrip productivity, but that is only because we have already hit very high productivity goals and exceeded them. Here are some of the metrics we examine:
Metrics
Percentage of project budgeted costs
Scope requirements
Total cost of ownership
Traceability
Defects rate (sev1, sev2, sev3 bugs - zero tolerance for sev1)
Completed requirements
Customer satisfaction scores (cust sats)
Schedule slippage
Flexibility of management styles
End-to-end throughput time per client-side user request
System extensibility
Scalability
Maintainability
Defects per thousand lines of code (KLOC or by function)
Support functionality and documentation availability, and completeness prior to launch
Rates of failure
Restoration (emergency)
Availability
Test effectiveness
Business acceptance
System acceptance (signoff)
Average turn around time for service and change requests
Number of security or privacy defects (last two should be zero tolerance in launch candidates)
Number of post freeze change requests
Among the mandatory metrics used are peer review effectiveness of code, and post mortems and overall customer satisfaction. In other words we do not consider just ontime delivery of products, enhancements, or new functionality.
What is our organization doing to improve productivity within its IT function?
Getting the right people – some people grew with us or came to us with deep knowledge from the school of hard knocks – work experience – we seek to capture the most knowledgeable and either increase their education or find those with both practical work experience and advanced degrees. Good thing this is Seattle with its heavily educated population. New programs at the university level such as Informatics and Information Management are producing the people we need – not just MBAs or Master of Comp Sci - because so much of our development work we outsource to India and developing countries, and IT is not traditionally closely aligned with marketing or sales. We do outsource much of the development work as is possible.
The undergrad Informatics and Master of Science in Information Management programs at the University of Washington are housed in Mary Gates' Hall, renovated and named in honor of Bill Gate's late mother, it's headed by Mike Crandall (Dublin Core, Microsoft, Boeing). So you can see this is the direction we are going regionally, because that is where the spend is. Another great information school is at the University of California at Berkeley, housed in one of the oldest and most architecturally beautiful collegiate buildings on the west coast, South Hall. On the physical level all Berkeley had to do is add wireless. Excellent academics such as the seminal thinker Dr Michael Buckland are there at Berkeley, and business leaders such as Mitch Kapor. Industry wide I think iSchools are having an effect, adding a more well rounded, even playful culture to high tech operations.
Improving and opening the culture is important. Having a shared lexicon is one of the benefits of educated people; those with MSIM (master of science in information management), Informatics, technical MBA degrees can comunicate effectively with highly technical people - this can produce enormous savings and long term cost benefits. Increased, clear, enthusiastic communication saves IT costs.
In strategy meetings, for example, we often include Enterprise Architects to assist in stack ranking program and project development, because this helps reduce redundant systems.
Our organization's ability to measure the return on investment (ROI) or success of its IT investments is “Fair but mixed,” we want ROI to be easily measureable and this means evaluating the correct things, asking the right questions in the first place, not following other organizations techniques, although we examine them as examples.
We are adding ways to evaluate our ROI – we do use business analysis methods. There is always an identifiable way to analyze and measure the relationship of what something costs even if it appears intangible such as Brand protection.
Considering the strategic and tactical stuff we are doing, at the core, creativity is what drives our success. Creativity is always a very difficult thing to measure. In fact it could be said that if you try, you are barking up the wrong tree. However creative thinking around practical goals has provided us success. This is where the ideas around flexibility and being very responsive come to play.
We have found very very high ROI around outsourced projects because they must be clearly defined within the Software Development Lifecycle (SDLC) and Sarbanes-Oxley Act of 2002 (SOX) compliance.
Those people who actually think out of the box are oftentimes not recognized by co-workers and management. Change is perceived as negative among full time staff. We seek to show support for both full time employees and consultants, and change this view and enhance their ability to communicate ideas. That is why our management keeps an open door policy. Unfortunately like any other policies the hazard is that individual managers must believe in our policies around openness and creativity; such self-selecting polices are impossible to enforce.
Our organization uses balanced scorecards, Six Sigma and other types of internally derived quantitative value measurement methods to measure the ROI or success of our IT investments.
The continued use of these methods we expect will substantially improve the management and measurement of our IT investments. Some of the metrics are at the discretion of the product or program manager, others are mandatory. In part we have some success- at issue is adopting metrics and measurement as well as Enterprise Architecture and engaging with open arms increased strategic thinking and planning.
Senior management must come together and present a unified strategy for the entire company – which is a top down management style but it must be embraced from the bottom up. This is within a framework of enforced change as we seek to achieve excellence in all of our business units, especially in core infrastructure – those units which either produce money, or cost money. Some of our key investments we know are lost leaders, but other research will more than make up for those. Enforced change in this context means business units receive minimum budget until they comply.
We are still feeling the effects of the changes the Web brings in enterprise directly and for our customers; we continue to learn from the effects of communities and communication via the Web. The opportunities for growth are so enormous that it is all the more important that we curb spending where it is not required and apply it as much as possible to grow in creative arenas which still have huge untapped profit potential. It is not just about money, among hard core technologists – those who really love it – money is secondary in many ways - it’s about the fun stuff technology can bring as well as the benefit to serve humanity that technology brings.
High tech, information technology, and software development have made some strides to maturity but we are still learning new things; it will be a learning industry, discovering and inventing stuff for a long time to come.
p.s.
Enforced Change is a radically different challenge, and promises different ways of looking at human-to-human, individual-to-corporation, corporate-to-corporate, human-to- computer interactions, etc, which I plan to cover in future articles, so stay tuned!
The skirt had heat and light pannels to feed the flowers, and some gutters to use the rain and water the ground. The legs are extensible so Tuli can feed the flowers giving the proper amount of light.
Nationaal Archief / Spaarnestad Photo / Het Leven / Fotograaf onbekend, SFA022818476.
Uitschuifbare caravan, gebouwd door een Franse ingenieur. Frankrijk, plaats onbekend, 1934.
Extensible caravan, built by a French engineer. France, location unknown, 1934.
Collectie Spaarnestad
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This guy apparently not happy being filmed.
Laced Woodpecker (Picus vittatus)
The laced woodpecker (Picus vittatus) is a species of bird in the Picidae family.
It is found in Cambodia, Indonesia, Laos, Malaysia, Myanmar, Singapore, Thailand, Vietnam and perhaps Bangladesh.
Its natural habitats are subtropical or tropical dry forests, subtropical or tropical moist lowland forests, subtropical or tropical mangrove forests, and subtropical or tropical moist montane forests.
Species: Laced Woodpecker Picus vittatus *
* The generic name stems from a Latin word: picus = woodpecker. (In Roman mythology, Picus, a brave warrior, was turned into a woodpecker by Circe, whose love he rejected. Seen as the god of agriculture, with the power of prophecy, he was widely worshipped in ancient Italy and was represented as a woodpecker, an important bird in augury.) In Latin, the species name vittatus = striped or banded.
Other common names: Bamboo Green Woodpecker, Laced Green Woodpecker, Small Scaly-bellied Woodpecker, Small Scaly-bellied Green Woodpecker.
Taxonomy: Picus vittatus Vieillot 1818, Java.
Sub-species & Distribution: The species ranges from S China down to Myanmar, Thailand, Malaysia, Singapore, Sumatra, Java and Bali. It is not found in Borneo. It is sometimes seen as being conspecific with the Streak-breasted Woodpecker Picus viridanus. Some authors consider it to be monotypic, while others recognise three sub-forms. The nominate form is found in Singapore and peninsular Malaysia, while another race, connectens, usually considered invalid, is found on Langkawi Island only.
Size: 10 to 11" (25.5 to 28.0 cm). Sexes slightly differ.
Description: Forehead and crown red, often finely streaked with black, extending onto the nape. Lores pale buffy-brown. A black patch above the lores, extending as a thin superciliary stripe along the sides of crown, with a fine white line below it starting just above the eye. Broad black moustachial streak from the base of lower mandible to the sides of the neck. Above it, a fine white streak starting from the base of upper mandible. Lower face grey, ear coverts darker, sides of nape and upper back bright greenish-brown. Mantle bright olive, the feathers edged yellowish-green, brighter on rump and uppertail coverts. Primaries brownish-black, with regular white bands on outer webs, secondaries similar with outer webs edged with bright olive, the white bands less distinct. Wing coverts dark olive tinged with metallic bronze, edged with greenish-yellow. The pointed tail feathers, stiffened by a strong central shaft except for the shorter outer pair, are blackish-brown, with whitish bars at regular intervals. Chin, throat and breast dull brownish-olive. Belly, lower abdomen and vent dark brownish-buff, the feathers being pale centrally and broadly edged with olive on both sides, producing a heavily striped appearance.
Females are very similar but have the top of the head entirely black. In immature birds, the green of the upperparts is duller than in adults, the face more greyish-brown and extending to the sides of the nape. The underparts are paler, the stripes much less distinct. Nestlings of both sexes have black crowns, the young males often acquiring red on the crown while still being fed by the parents.
Soft parts: Iris wine-red, dark brown in young birds, eye-ring greenish-grey. Tarsus greenish-horn. Upper mandible black, sometimes marked with yellow and paler at tip, lower mandible yellow at base, darker at tip.
Similar species: This species very closely resembles the Streak-breasted Woodpecker Picus viridanus which is not found in Singapore but does occur in peninsular Malaysia.
Picus vittatus: Chin, throat and upper breast dull brownish-olive, with no streaks. Lower breast dark brownish-buff with fine lacy marks.
Picus viridanus: Throat greener, lightly streaked. Entire breast green, with bold scaly streaks.
Status, Habitat & Behaviour: A coastal species found in the casuarinas and mangrove belt from Perak down to Johore and Singapore, it is common on both sides of the Johore Straits but is rarely found inland (Robinson & Chasen 1939). While Burknill & Chasen (1927) considered it unlikely to be found in gardens or near town, the degree of forest clearance since then may have changed things somewhat.
Medway & Wells (1976) found it in mangrove and adjacent secondary growth to, at the most, 24 km inland in coconut plantations and village gardens. Wells (1999) found it common near the coast, less so inland, but noted its landward expansion, particularly since 1970's, into oil palm and rubber plantations, nearby wooded gardens and parkland up to 30 km from the sea, but strictly at plains level.
Since the early 1900's, there has been much debate, and confusion, over its taxonomy, as well as its status and relationships to very similar birds, such as the Streak-breasted Woodpecker Picus viridanus and the Streak-throated Woodpecker Picus xanthopygaeus, found in peninsular Malaya, Thailand and Myanmar. This debate still continues, and further taxonomic migration can be anticipated. As a result, very little of the early data, on its habits and behaviour, can safely be ascribed to this species.
Found singly, in pairs or in small family parties, it is not a shy bird. Most often, it is seen on tree trunks, its tail depressed and partly fanned out to support it against the bark, climbing upwards, often going round and round the trunk in short jerky movements, sometimes hopping backwards for a pace or two. Every now and again, it stops and, with its head cocked to one side, peers very intently at the tree bark, possibly to listen for activity beneath the bark, occasionally tapping tentatively at the bark with its bill. Whenever it suspects the presence of its prey, it starts pecking furiously away, vigorously enough to send wood chips flying all around it, then inserts its tongue into the cavity to extract food.
The bird frequently finds its food on the fallen trunks of trees, in tall grass, and can regularly be seen feeding on the ground, the tail pressed against the ground, the body held upright. The underparts of several museum specimens were sullied with mud, suggesting that the birds had fed on the ground or on the roots of mangrove (Burknill & Chasen 1927). In Perak, they were seen searching for food among the fallen leaves in a rubber estate (Edgar 1933). A pair was seen feeding on the ground in Singapore too (Kwong 2011).
Occasionally, it can be seen perched on tree trunks or stumps, sunning itself with one or both wings partly outstretched. When disturbed, it flies a short distance to land on the lower branches of a nearby tree. Its flight is strong and undulating.
Food: Like all woodpeckers, it feeds mainly on termites, ants and other small insects, including the larvae and eggs of wood-boring insects, hidden in decaying wood or within the hollow stems of various plants. It finds its prey by chiselling into the rotting wood. Then, using its long and greatly extensible tongue, the barbed tip covered with glutinous saliva, it probes deep into the cavity to extract the prey. In Singapore, a bird was seen on the ground, apparently eating worms (Jane 2010).
There is very little by way of detailed information specific to its diet but it has been known to eat fruit and berries. A congeneric species, the Streak-throated Woodpecker Picus xanthopygaeus, takes the nectar of flowers from the Erythrina and Salmalia trees, and drinks juice from date palms tapped for toddy (Ali & Ripley 1970). From Singapore, there are reports of this bird feeding at a durian tree Durio zibethinus (Goh et al 2006), and on an oil palm tree Elaeis guineensis (Chow 2011) - whether the bird was actually eating the fruit, drinking the sap or feeding on insects remains unclear. Additionally, there is an early record, from 1989, of this bird being seen "pecking and gobbling the juicy flesh of rambutans" but the actual source of this citation, however, remains elusive.
Voice and Calls: Its call is a high-pitched and fairly loud kek, repeated about a dozen times, every two to three seconds or so.
Breeding: In Singapore, nest building has been recorded from December to April and June, brooding in April and May, chicks in June, and young birds were seen in June and August (Wang & Hails 2007). In Perak, West Malaysia, nests were found from March to April (Edgar 1933). Medway & Wells (1976) have recorded nests between February and June.
Like all woodpeckers, it nests in holes excavated into tree trunks. Their nests, situated 1 to 9 m (3 to 30 feet) above the ground level, have been found on an "api-api' tree (Avicennia spp.), dead coconut trees Cocos nucifera, on a hog-plum tree Spondias spp, a dead mango tree Mangifera spp (Edgar 1933) and on a casuarina tree (Madoc 1956). Though it appears to nest mainly on dead trunks, some nests have been excavated into living trees (Wells 1999).
The normal clutch consists of four eggs, pinkish-white, fairly glossy, the average size varying from 26.4 x 19.1 mm. to 27.4 x 21.1 mm. (Edgar 1933). Both sexes help excavate the nest, incubate the eggs and feed the young. Very little is known of its courtship behaviour or its breeding biology.
Moult: In Genus Picidae, the primaries moult descendantly and sequentially, the secondaries from two centres, ascendantly from S1 (starting after P5), ascendantly and descendantly from S8 (starting with P3). Tail moult is centrifugal. Post-nuptial is complete. Post-juvenile moult is partial, of primaries, tail and body but not the secondaries, primary coverts or tertials though, sometimes, one or two tertials may be replaced. Occasionally, the outer primary coverts are also moulted, with contrast between the new and old feathers showing (Baker 1993).
On 26th August, a family party of two adults and an immature bird was caught at Ulu Pandan in Singapore. The male, with an ill-defined brood patch, was in post-nuptial moult. Wing: P1 to P4 = 5, P5 = 3, P6 = 1, rest = 0, S1 = 4, S2 to S5 = 0, S6 to S8 = 5. Tail: T1 = 0, T2 = 2, T3 = 1, rest = 0. The female, with a distinct brood patch, was also in post-nuptial moult. Wing: P1 to P3 = 5, P4 = 4, P5 = 2, rest = 0. S1 to S6 = 0, S7 to S8 = 5. Tail: T1 = 0, T2 = 1, rest = 0. The immature bird, a female, was undergoing post-juvenile moult. Wing: P1 to P2 = 5, P3 = 4, P4 = missing, rest = 0 (Wang 1999).
Miscellaneous: Generally speaking, birds are said to have very little sense of smell or taste. Whether woodpeckers have an acute sense of hearing which enables them to detect the movements of prey items hidden within the wood or whether tapping at the wood with the bill enables them to locate any prey in hidden hollows beneath the surface of the wood, is not entirely clear.
The bone structure in a woodpecker's skull is part of an evolutionary adaptation that enables it to hammer away into tree trunks without suffering damage to its brain. Its tongue, too, often more than twice the length of the bird's skull, is just as specialised. More information about this can be obtained from the ON Nature magazine, or the Wild Birds Unlimited site.
To discover how the development of the woodpecker's skull has helped inspire the development of shock absorbers, please visit this page published in the New Scientist. The original paper it cites, a highly technical and detailed effort, A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems (Yoon & Park 2011), can be obtained at the IOPscience website.
Two adult birds ringed at Rantau Panjang were recaptured there 116 and 120 months later (Medway & Wells 1976).
[Credit: singaporebirds.net/]
This small fish grows up to 22 cm (8.7 in) long. Like other members of its family, it has a rounded, extensible body, and its soft skin is covered with irregularly-arranged dermal spinules resembling hairs. Its large mouth is forwardly extensible, allowing it to swallow prey as large as itself. The coloring of its body is extremely variable because individual fish tend to match their living environments. Frogfishes have the capacity to change coloration and pigment pattern, taking only a few weeks to adapt. The dominant coloration varies from yellow to brownish-orange, passing through a range of shades, but it can also be green, gray, brown, almost white, or even completely black without any pattern. Body and fins can be marked with roughly parallel dark stripes or elongated blotches, some with rays radiating outward from the eye. This one is angling for its food. Sabang, Puerto Galera, Mindoro Oriental, Philippines
Playable features of the crane include removable cab roof, scissor lift cab, chain winch, extensible boom, and the hinged cheese claw.
For more photos, see the full set.
Aston Martin DB5 1964
Échelle/Scale 1/24
Un autre modèle assemblé mais délabré trouvé au fond de mon rangement et qui a échappé de justesse à la casse. Ce kit reproduisait la célèbre monture de James Bond et comprenait tous ses gadgets : mitrailleuses sous les phares avant, blindage escamotable à l'arrière, plaques d'immatriculation interchangeables, déchiqueteuses extensibles dans les moyeux de roue et naturellement le siège passager pouvant éjecter son occupant (fonctionnant avec un ressort). Malheureusement (?) ces gadgets étaient soit perdus, soit brisés, et j'ai donc décidé de les mettre de côté et de refaire le modèle en version standard. Un problème plus embêtant est que je n'ai retrouvé que trois roues. Heureusement un autre modèle démoli dans la même boîte (une Toyota 2000GT) possédait des roues similaires et je les ai subtilisées. La seule différence est que les roues de la Toyota ont des écrous à 2 ailettes alors que la DB5 avait habituellement des écrous à 3 ailettes, mais on peut bien se permettre un peu de créativité, quoi. Mais que vais-je faire de la Toyota 2000GT? Avec un peu (beaucoup) de chance, je retrouverai d'ici là la roue manquante de l'Aston Martin...
/
Another already built model found in the back of my storage place and one that had escaped from the garbage can by a very slight margin. This was a kit of the James Bond's iconic car and was issued with all the gadgets of the original machine: guns behind the front lights, retractable rear window armour plate, alternative license plate changer, extending wheel spinners/shredders and of course actually working spring-loaded passenger ejector seat. Unfortunately (?) these gadgets were either lost or broken, so I decided to discard them and build a standard DB5. A more annoying problem was the loss of one wheel but fortunately I found a complete and almost similar set on another kit in the scrapyard box (a Toyota 2000GT). The only difference is that the Toyota wheels has two wings on the spinner while the DB5 usually has three, but hey, why not a little creativity there. What will I do if I decide to rebuild the Toyota 2000? Maybe I will be lucky and at that time I will possibly have found back the DB5 missing wheel...
François
Eruei wanted the ultimate assistant to have infinitely extensible limbs, so tried to develop a system in which most of the length of them would be stored in an alternative dimension. Didn't work, and the model he was using colapsed into the nothingness.
Or so it seemed, as Aigara and her friends would find parts of it around their travels. Will something happen if all its parts get reunited?
MOC nº: 036.
Creation order: ???.
Title: Doll Warper.
Nickname: "Womi" (by Aigara).
Color trait: Transparent Light Blue.
Functionality: Failure (originally Assistance).
Abilities: Interdimensional gates connecting its body parts.
Current state: Unknown.
Beaucoup de geckos australiens vivent dans des zones désertiques ou sur le littoral et sont donc très souvent exposés à la poussière ou au sable. La plupart utilisent donc la même technique afin de nettoyer leurs yeux : ils se servent de leur langue extensible comme « d’essuie-glace » à gauche, puis à droite.
Many Australian geckos live in desert or on the coastline and are therefore very often exposed to dust and sand. Most of them use the same technique to clean their eyes: They use their stretchy tongue as a "wiper" on the left, and then on the right.
This is the poster shot for my SHIPtember entry. Biography and data is included below.
Imsari Mar -ak Wvelest "Dreadnought"-class Starcrawler
The Imsari are a people of the stars. Their worlds have no atmospheres and significant gravity, making the vast beyond seem so much closer yet so much harder to reach. As a musical, magic-believing society, the beings were utterly astonished when a "hum star" landed on their isolated homeworld, and offered them the first opportunity for exploring the stars.
To the civilized galaxy-spanning government that discovered them, the natives were uncouth, uncivilized, ritual-chanting aboriginals. Such was the only message ever to leave this scout vessel, before it was systematically attacked and overrun by the "uncivilized" natives. Presented with technologies beyond their comprehension, they resorted to magic and music to decipher the secrets of the vehicle.
Within 200 years, the species was at a modern-age equivalent and manufacturing its own starships. Eventually, they took to the sky and achieved warp, the only technology they could not directly replicate from the vessel they commandeered. Although they could travel faster than light, the speed was much slower than conventional FTL travel, requiring a time of nearly three months to travel the 341 parsecs that distanced their most extreme colony planet from their homeworld.
If there is a people in the galaxy that is a symbol of possibility, tenacity, and victory, it is the Imsari. In little over 500 years, this culture first encountered space travel and replicated it for themselves, colonizing 5 star systems, and setting up a black-market commerce with the lead inhabitant population of the galaxy. Yet they are also a master of disguises and trickery, and no being has ever claimed to know the mysterious aliens' true identity. The only clue of their whereabouts, lifestyle, and culture lies in a hastily encoded message sent from a scout ship lost to time nearly half a millennium ago...
Data:
Length (real): 112.5 studs
Length (fictitious): 450 meters
Conversion rate: 1 stud = 4 meters
Weight: ~6.5 lbs
Purpose: Colony Defense and Transportation
Make: Dreadnought-class Starcrawler
Model: Mar -ak Wvelest #17
(Translation: Instrument of the Celestials, 17th produced)
Defense: 14 anti-vehicular turrets with 100° pan and 120° incline. Shielded docking/landing bay.
Offense: Quadruple "Metal-slicer" anti-establishment cannon on bow + "Death Ray" ionization beam emitter on bow.
Thrust: Triple fusion-reaction engines astern of the reactor core.
Central Power: Large, bulbous reactor core (studded).
Maneuverability: Minimal atmospheric maneuverability using 2 port and 2 starboard fins; these are also used to transform light into energy. In space, small guidance rockets are used.
Communications: Twin signal-boosting full-frequency-spectrum regulators and four individually-aligned satellite receivers.
Capacity: 4500 passengers; 800 crew and military personnel. One squadron (12 units) of starfighters; 6 docking tubes for bombers; 4 docking tubes for shuttles; 1 docking clamp for a transport.
Accessibility: 1 port and 1 starboard extensible docking tube, compatible with larger SHIPS such as superfreighters, used for restocking of supplies.
Crawlspace technology: 8 divisional drill focuses and a single governing drill. Can be operated independently of planetary drills.
Control Systems: Forward, ventral bridge control; docking bay control aft of docking bay.
Imbrium Lunokhod Industries Model VS-MU-333 'Lorikeet' is the next step in Imbrium Lunokhod Industries Frame System. This mass produced frame builds on the versatile and flexible mobile frame platform made popular by the VS-M/S-71 'Degei' (flic.kr/s/aHsm37uTTm) and the VS-MX-04 'Rangi' (flic.kr/s/aHsk4AUkEY). Developed for planetary surface operations and utility deployments, the Lorikeet will definitely not excel in zero-g environments, it's outclassed by more maneuverable specialty frames. But for deployments to planetary surfaces, the frame offers a more affordable (although less durable) alternative to the Varuna (flic.kr/s/aHsm89p5MW) the a more extensible (and repairable) alternative to the Krivlyaka (flic.kr/s/aHsm4d6e2v).
From a design perspective, the frame takes a ton of inspiration from both Malcolm Craig's MgN-333 (flic.kr/p/dEFocc) and Aardvark17's Budgie (flic.kr/p/2kgyyua) frames as well as my version of the HR-13 flic.kr/s/aHsmMLcB3m.
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Built for Mobile Frame Zero - a tabletop wargame.
Mobile Frame Hangar Nova (MFZ Community Forums).
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Jellyfish, also known sea jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.
Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle. The medusa is normally the sexual phase, which produces planula larvae; these then disperse widely and enter a sedentary polyp phase, before reaching sexual maturity.
Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the "true jellyfish") are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal group.
Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomeae order are pressed and salted to remove excess water. Australian researchers have described them as a "perfect food": sustainable and protein-rich but relatively low in food energy.
They are also used in research, where the green fluorescent protein used by some species to cause bioluminescence has been adapted as a fluorescent marker for genes inserted into other cells or organisms.
The stinging cells used by jellyfish to subdue their prey can injure humans. Thousands of swimmers worldwide are stung every year, with effects ranging from mild discomfort to serious injury or even death. When conditions are favourable, jellyfish can form vast swarms, which can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea.
Names
The name jellyfish, in use since 1796, has traditionally been applied to medusae and all similar animals including the comb jellies (ctenophores, another phylum). The term jellies or sea jellies is more recent, having been introduced by public aquaria in an effort to avoid use of the word "fish" with its modern connotation of an animal with a backbone, though shellfish, cuttlefish and starfish are not vertebrates either. In scientific literature, "jelly" and "jellyfish" have been used interchangeably. Many sources refer to only scyphozoans as "true jellyfish".
A group of jellyfish is called a "smack" or a "smuck".
Definition
The term jellyfish broadly corresponds to medusae, that is, a life-cycle stage in the Medusozoa. The American evolutionary biologist Paulyn Cartwright gives the following general definition:
Typically, medusozoan cnidarians have a pelagic, predatory jellyfish stage in their life cycle; staurozoans are the exceptions [as they are stalked].
The Merriam-Webster dictionary defines jellyfish as follows:
A free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells.
Given that jellyfish is a common name, its mapping to biological groups is inexact. Some authorities have called the comb jellies and certain salps jellyfish, though other authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa.
The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with on the following cladogram of the animal kingdom:
Jellyfish are not a clade, as they include most of the Medusozoa, barring some of the Hydrozoa. The medusozoan groups included by authorities are indicated on the following phylogenetic tree by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface; the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish.
Taxonomy
The subphylum Medusozoa includes all cnidarians with a medusa stage in their life cycle. The basic cycle is egg, planula larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, Scyphozoa (large jellyfish), Cubozoa (box jellyfish) and Hydrozoa (small jellyfish), and excludes Anthozoa (corals and sea anemones). This suggests that the medusa form evolved after the polyps. Medusozoans have tetramerous symmetry, with parts in fours or multiples of four.
The four major classes of medusozoan Cnidaria are:
Scyphozoa are sometimes called true jellyfish, though they are no more truly jellyfish than the others listed here. They have tetra-radial symmetry. Most have tentacles around the outer margin of the bowl-shaped bell, and long, oral arms around the mouth in the center of the subumbrella.
Cubozoa (box jellyfish) have a (rounded) box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to scyphozoan jellyfish than either are to the Hydrozoa.
Hydrozoa medusae also have tetra-radial symmetry, nearly always have a velum (diaphragm used in swimming) attached just inside the bell margin, do not have oral arms, but a much smaller central stalk-like structure, the manubrium, with terminal mouth opening, and are distinguished by the absence of cells in the mesoglea. Hydrozoa show great diversity of lifestyle; some species maintain the polyp form for their entire life and do not form medusae at all (such as Hydra, which is hence not considered a jellyfish), and a few are entirely medusal and have no polyp form.
Staurozoa (stalked jellyfish) are characterized by a medusa form that is generally sessile, oriented upside down and with a stalk emerging from the apex of the "calyx" (bell), which attaches to the substrate. At least some Staurozoa also have a polyp form that alternates with the medusoid portion of the life cycle. Until recently, Staurozoa were classified within the Scyphozoa.
There are over 200 species of Scyphozoa, about 50 species of Staurozoa, about 50 species of Cubozoa, and the Hydrozoa includes about 1000–1500 species that produce medusae, but many more species that do not.
Fossil history
Since jellyfish have no hard parts, fossils are rare. The oldest unambiguous fossil of a free-swimming medusa is Burgessomedusa from the mid Cambrian Burgess Shale of Canada, which is likely either a stem group of box jellyfish (Cubozoa) or Acraspeda (the clade including Staurozoa, Cubozoa, and Scyphozoa). Other claimed records from the Cambrian of China and Utah in the United States are uncertain, and possibly represent ctenophores instead.
Anatomy
The main feature of a true jellyfish is the umbrella-shaped bell. This is a hollow structure consisting of a mass of transparent jelly-like matter known as mesoglea, which forms the hydrostatic skeleton of the animal. 95% or more of the mesogloea consists of water, but it also contains collagen and other fibrous proteins, as well as wandering amoebocytes which can engulf debris and bacteria. The mesogloea is bordered by the epidermis on the outside and the gastrodermis on the inside. The edge of the bell is often divided into rounded lobes known as lappets, which allow the bell to flex. In the gaps or niches between the lappets are dangling rudimentary sense organs known as rhopalia, and the margin of the bell often bears tentacles.
Anatomy of a scyphozoan jellyfish
On the underside of the bell is the manubrium, a stalk-like structure hanging down from the centre, with the mouth, which also functions as the anus, at its tip. There are often four oral arms connected to the manubrium, streaming away into the water below. The mouth opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. This is subdivided by four thick septa into a central stomach and four gastric pockets. The four pairs of gonads are attached to the septa, and close to them four septal funnels open to the exterior, perhaps supplying good oxygenation to the gonads. Near the free edges of the septa, gastric filaments extend into the gastric cavity; these are armed with nematocysts and enzyme-producing cells and play a role in subduing and digesting the prey. In some scyphozoans, the gastric cavity is joined to radial canals which branch extensively and may join a marginal ring canal. Cilia in these canals circulate the fluid in a regular direction.
Discharge mechanism of a nematocyst
The box jellyfish is largely similar in structure. It has a squarish, box-like bell. A short pedalium or stalk hangs from each of the four lower corners. One or more long, slender tentacles are attached to each pedalium. The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates, allowing box jellyfish to swim faster than true jellyfish. Hydrozoans are also similar, usually with just four tentacles at the edge of the bell, although many hydrozoans are colonial and may not have a free-living medusal stage. In some species, a non-detachable bud known as a gonophore is formed that contains a gonad but is missing many other medusal features such as tentacles and rhopalia. Stalked jellyfish are attached to a solid surface by a basal disk, and resemble a polyp, the oral end of which has partially developed into a medusa with tentacle-bearing lobes and a central manubrium with four-sided mouth.
Most jellyfish do not have specialized systems for osmoregulation, respiration and circulation, and do not have a central nervous system. Nematocysts, which deliver the sting, are located mostly on the tentacles; true jellyfish also have them around the mouth and stomach. Jellyfish do not need a respiratory system because sufficient oxygen diffuses through the epidermis. They have limited control over their movement, but can navigate with the pulsations of the bell-like body; some species are active swimmers most of the time, while others largely drift. The rhopalia contain rudimentary sense organs which are able to detect light, water-borne vibrations, odour and orientation. A loose network of nerves called a "nerve net" is located in the epidermis. Although traditionally thought not to have a central nervous system, nerve net concentration and ganglion-like structures could be considered to constitute one in most species. A jellyfish detects stimuli, and transmits impulses both throughout the nerve net and around a circular nerve ring, to other nerve cells. The rhopalial ganglia contain pacemaker neurones which control swimming rate and direction.
In many species of jellyfish, the rhopalia include ocelli, light-sensitive organs able to tell light from dark. These are generally pigment spot ocelli, which have some of their cells pigmented. The rhopalia are suspended on stalks with heavy crystals at one end, acting like gyroscopes to orient the eyes skyward. Certain jellyfish look upward at the mangrove canopy while making a daily migration from mangrove swamps into the open lagoon, where they feed, and back again.
Box jellyfish have more advanced vision than the other groups. Each individual has 24 eyes, two of which are capable of seeing colour, and four parallel information processing areas that act in competition, supposedly making them one of the few kinds of animal to have a 360-degree view of its environment.
Box jellyfish eye
The study of jellyfish eye evolution is an intermediary to a better understanding of how visual systems evolved on Earth. Jellyfish exhibit immense variation in visual systems ranging from photoreceptive cell patches seen in simple photoreceptive systems to more derived complex eyes seen in box jellyfish. Major topics of jellyfish visual system research (with an emphasis on box jellyfish) include: the evolution of jellyfish vision from simple to complex visual systems), the eye morphology and molecular structures of box jellyfish (including comparisons to vertebrate eyes), and various uses of vision including task-guided behaviors and niche specialization.
Evolution
Experimental evidence for photosensitivity and photoreception in cnidarians antecedes the mid 1900s, and a rich body of research has since covered evolution of visual systems in jellyfish. Jellyfish visual systems range from simple photoreceptive cells to complex image-forming eyes. More ancestral visual systems incorporate extraocular vision (vision without eyes) that encompass numerous receptors dedicated to single-function behaviors. More derived visual systems comprise perception that is capable of multiple task-guided behaviors.
Although they lack a true brain, cnidarian jellyfish have a "ring" nervous system that plays a significant role in motor and sensory activity. This net of nerves is responsible for muscle contraction and movement and culminates the emergence of photosensitive structures. Across Cnidaria, there is large variation in the systems that underlie photosensitivity. Photosensitive structures range from non-specialized groups of cells, to more "conventional" eyes similar to those of vertebrates. The general evolutionary steps to develop complex vision include (from more ancestral to more derived states): non-directional photoreception, directional photoreception, low-resolution vision, and high-resolution vision. Increased habitat and task complexity has favored the high-resolution visual systems common in derived cnidarians such as box jellyfish.
Basal visual systems observed in various cnidarians exhibit photosensitivity representative of a single task or behavior. Extraocular photoreception (a form of non-directional photoreception), is the most basic form of light sensitivity and guides a variety of behaviors among cnidarians. It can function to regulate circadian rhythm (as seen in eyeless hydrozoans) and other light-guided behaviors responsive to the intensity and spectrum of light. Extraocular photoreception can function additionally in positive phototaxis (in planula larvae of hydrozoans), as well as in avoiding harmful amounts of UV radiation via negative phototaxis. Directional photoreception (the ability to perceive direction of incoming light) allows for more complex phototactic responses to light, and likely evolved by means of membrane stacking. The resulting behavioral responses can range from guided spawning events timed by moonlight to shadow responses for potential predator avoidance. Light-guided behaviors are observed in numerous scyphozoans including the common moon jelly, Aurelia aurita, which migrates in response to changes in ambient light and solar position even though they lack proper eyes.
The low-resolution visual system of box jellyfish is more derived than directional photoreception, and thus box jellyfish vision represents the most basic form of true vision in which multiple directional photoreceptors combine to create the first imaging and spatial resolution. This is different from the high-resolution vision that is observed in camera or compound eyes of vertebrates and cephalopods that rely on focusing optics. Critically, the visual systems of box jellyfish are responsible for guiding multiple tasks or behaviors in contrast to less derived visual systems in other jellyfish that guide single behavioral functions. These behaviors include phototaxis based on sunlight (positive) or shadows (negative), obstacle avoidance, and control of swim-pulse rate.
Box jellyfish possess "proper eyes" (similar to vertebrates) that allow them to inhabit environments that lesser derived medusae cannot. In fact, they are considered the only class in the clade Medusozoa that have behaviors necessitating spatial resolution and genuine vision. However, the lens in their eyes are more functionally similar to cup-eyes exhibited in low-resolution organisms, and have very little to no focusing capability. The lack of the ability to focus is due to the focal length exceeding the distance to the retina, thus generating unfocused images and limiting spatial resolution. The visual system is still sufficient for box jellyfish to produce an image to help with tasks such as object avoidance.
Utility as a model organism
Box jellyfish eyes are a visual system that is sophisticated in numerous ways. These intricacies include the considerable variation within the morphology of box jellyfishes' eyes (including their task/behavior specification), and the molecular makeup of their eyes including: photoreceptors, opsins, lenses, and synapses. The comparison of these attributes to more derived visual systems can allow for a further understanding of how the evolution of more derived visual systems may have occurred, and puts into perspective how box jellyfish can play the role as an evolutionary/developmental model for all visual systems.
Characteristics
Box jellyfish visual systems are both diverse and complex, comprising multiple photosystems. There is likely considerable variation in visual properties between species of box jellyfish given the significant inter-species morphological and physiological variation. Eyes tend to differ in size and shape, along with number of receptors (including opsins), and physiology across species of box jellyfish.
Box jellyfish have a series of intricate lensed eyes that are similar to those of more derived multicellular organisms such as vertebrates. Their 24 eyes fit into four different morphological categories. These categories consist of two large, morphologically different medial eyes (a lower and upper lensed eye) containing spherical lenses, a lateral pair of pigment slit eyes, and a lateral pair of pigment pit eyes. The eyes are situated on rhopalia (small sensory structures) which serve sensory functions of the box jellyfish and arise from the cavities of the exumbrella (the surface of the body) on the side of the bells of the jellyfish. The two large eyes are located on the mid-line of the club and are considered complex because they contain lenses. The four remaining eyes lie laterally on either side of each rhopalia and are considered simple. The simple eyes are observed as small invaginated cups of epithelium that have developed pigmentation. The larger of the complex eyes contains a cellular cornea created by a mono ciliated epithelium, cellular lens, homogenous capsule to the lens, vitreous body with prismatic elements, and a retina of pigmented cells. The smaller of the complex eyes is said to be slightly less complex given that it lacks a capsule but otherwise contains the same structure as the larger eye.
Box jellyfish have multiple photosystems that comprise different sets of eyes. Evidence includes immunocytochemical and molecular data that show photopigment differences among the different morphological eye types, and physiological experiments done on box jellyfish to suggest behavioral differences among photosystems. Each individual eye type constitutes photosystems that work collectively to control visually guided behaviors.
Box jellyfish eyes primarily use c-PRCs (ciliary photoreceptor cells) similar to that of vertebrate eyes. These cells undergo phototransduction cascades (process of light absorption by photoreceptors) that are triggered by c-opsins. Available opsin sequences suggest that there are two types of opsins possessed by all cnidarians including an ancient phylogenetic opsin, and a sister ciliary opsin to the c-opsins group. Box jellyfish could have both ciliary and cnidops (cnidarian opsins), which is something not previously believed to appear in the same retina. Nevertheless, it is not entirely evident whether cnidarians possess multiple opsins that are capable of having distinctive spectral sensitivities.
Comparison with other organisms
Comparative research on genetic and molecular makeup of box jellyfishes' eyes versus more derived eyes seen in vertebrates and cephalopods focuses on: lenses and crystallin composition, synapses, and Pax genes and their implied evidence for shared primordial (ancestral) genes in eye evolution.
Box jellyfish eyes are said to be an evolutionary/developmental model of all eyes based on their evolutionary recruitment of crystallins and Pax genes. Research done on box jellyfish including Tripedalia cystophora has suggested that they possess a single Pax gene, PaxB. PaxB functions by binding to crystallin promoters and activating them. PaxB in situ hybridization resulted in PaxB expression in the lens, retina, and statocysts. These results and the rejection of the prior hypothesis that Pax6 was an ancestral Pax gene in eyes has led to the conclusion that PaxB was a primordial gene in eye evolution, and that the eyes of all organisms likely share a common ancestor.
The lens structure of box jellyfish appears very similar to those of other organisms, but the crystallins are distinct in both function and appearance. Weak reactions were seen within the sera and there were very weak sequence similarities within the crystallins among vertebrate and invertebrate lenses. This is likely due to differences in lower molecular weight proteins and the subsequent lack of immunological reactions with antisera that other organisms' lenses exhibit.
All four of the visual systems of box jellyfish species investigated with detail (Carybdea marsupialis, Chiropsalmus quadrumanus, Tamoya haplonema and Tripedalia cystophora) have invaginated synapses, but only in the upper and lower lensed eyes. Different densities were found between the upper and lower lenses, and between species. Four types of chemical synapses have been discovered within the rhopalia which could help in understanding neural organization including: clear unidirectional, dense-core unidirectional, clear bidirectional, and clear and dense-core bidirectional. The synapses of the lensed eyes could be useful as markers to learn more about the neural circuit in box jellyfish retinal areas.
Evolution as a response to natural stimuli
The primary adaptive responses to environmental variation observed in box jellyfish eyes include pupillary constriction speeds in response to light environments, as well as photoreceptor tuning and lens adaptations to better respond to shifts between light environments and darkness. Interestingly, some box jellyfish species' eyes appear to have evolved more focused vision in response to their habitat.
Pupillary contraction appears to have evolved in response to variation in the light environment across ecological niches across three species of box jellyfish (Chironex fleckeri, Chiropsella bronzie, and Carukia barnesi). Behavioral studies suggest that faster pupil contraction rates allow for greater object avoidance, and in fact, species with more complex habitats exhibit faster rates. Ch. bronzie inhabit shallow beach fronts that have low visibility and very few obstacles, thus, faster pupil contraction in response to objects in their environment is not important. Ca. barnesi and Ch. fleckeri are found in more three-dimensionally complex environments like mangroves with an abundance of natural obstacles, where faster pupil contraction is more adaptive. Behavioral studies support the idea that faster pupillary contraction rates assist with obstacle avoidance as well as depth adjustments in response to differing light intensities.
Light/dark adaptation via pupillary light reflexes is an additional form of an evolutionary response to the light environment. This relates to the pupil's response to shifts between light intensity (generally from sunlight to darkness). In the process of light/dark adaptation, the upper and lower lens eyes of different box jellyfish species vary in specific function. The lower lens-eyes contain pigmented photoreceptors and long pigment cells with dark pigments that migrate on light/dark adaptation, while the upper-lens eyes play a concentrated role in light direction and phototaxis given that they face upward towards the water surface (towards the sun or moon). The upper lens of Ch. bronzie does not exhibit any considerable optical power while Tr. cystophora (a box jellyfish species that tends to live in mangroves) does. The ability to use light to visually guide behavior is not of as much importance to Ch. bronzie as it is to species in more obstacle-filled environments. Differences in visually guided behavior serve as evidence that species that share the same number and structure of eyes can exhibit differences in how they control behavior.
Largest and smallest
Jellyfish range from about one millimeter in bell height and diameter, to nearly 2 metres (6+1⁄2 ft) in bell height and diameter; the tentacles and mouth parts usually extend beyond this bell dimension.
The smallest jellyfish are the peculiar creeping jellyfish in the genera Staurocladia and Eleutheria, which have bell disks from 0.5 millimetres (1⁄32 in) to a few millimeters in diameter, with short tentacles that extend out beyond this, which these jellyfish use to move across the surface of seaweed or the bottoms of rocky pools; many of these tiny creeping jellyfish cannot be seen in the field without a hand lens or microscope. They can reproduce asexually by fission (splitting in half). Other very small jellyfish, which have bells about one millimeter, are the hydromedusae of many species that have just been released from their parent polyps; some of these live only a few minutes before shedding their gametes in the plankton and then dying, while others will grow in the plankton for weeks or months. The hydromedusae Cladonema radiatum and Cladonema californicum are also very small, living for months, yet never growing beyond a few mm in bell height and diameter.
The lion's mane jellyfish, Cyanea capillata, was long-cited as the largest jellyfish, and arguably the longest animal in the world, with fine, thread-like tentacles that may extend up to 36.5 m (119 ft 9 in) long (though most are nowhere near that large). They have a moderately painful, but rarely fatal, sting. The increasingly common giant Nomura's jellyfish, Nemopilema nomurai, found in some, but not all years in the waters of Japan, Korea and China in summer and autumn is another candidate for "largest jellyfish", in terms of diameter and weight, since the largest Nomura's jellyfish in late autumn can reach 2 m (6 ft 7 in) in bell (body) diameter and about 200 kg (440 lb) in weight, with average specimens frequently reaching 0.9 m (2 ft 11 in) in bell diameter and about 150 kg (330 lb) in weight. The large bell mass of the giant Nomura's jellyfish can dwarf a diver and is nearly always much greater than the Lion's Mane, whose bell diameter can reach 1 m (3 ft 3 in).
The rarely encountered deep-sea jellyfish Stygiomedusa gigantea is another candidate for "largest jellyfish", with its thick, massive bell up to 100 cm (3 ft 3 in) wide, and four thick, "strap-like" oral arms extending up to 6 m (19+1⁄2 ft) in length, very different from the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane.
Desmonema glaciale, which lives in the Antarctic region, can reach a very large size (several meters). Purple-striped jelly (Chrysaora colorata) can also be extremely long (up to 15 feet).
Life history and behavior
Life cycle
Jellyfish have a complex life cycle which includes both sexual and asexual phases, with the medusa being the sexual stage in most instances. Sperm fertilize eggs, which develop into larval planulae, become polyps, bud into ephyrae and then transform into adult medusae. In some species certain stages may be skipped.
Upon reaching adult size, jellyfish spawn regularly if there is a sufficient supply of food. In most species, spawning is controlled by light, with all individuals spawning at about the same time of day; in many instances this is at dawn or dusk. Jellyfish are usually either male or female (with occasional hermaphrodites). In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae. In a few species, the sperm swim into the female's mouth, fertilizing the eggs within her body, where they remain during early development stages. In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae.
The planula is a small larva covered with cilia. When sufficiently developed, it settles onto a firm surface and develops into a polyp. The polyp generally consists of a small stalk topped by a mouth that is ringed by upward-facing tentacles. The polyps resemble those of closely related anthozoans, such as sea anemones and corals. The jellyfish polyp may be sessile, living on the bottom, boat hulls or other substrates, or it may be free-floating or attached to tiny bits of free-living plankton or rarely, fish or other invertebrates. Polyps may be solitary or colonial. Most polyps are only millimetres in diameter and feed continuously. The polyp stage may last for years.
After an interval and stimulated by seasonal or hormonal changes, the polyp may begin reproducing asexually by budding and, in the Scyphozoa, is called a segmenting polyp, or a scyphistoma. Budding produces more scyphistomae and also ephyrae. Budding sites vary by species; from the tentacle bulbs, the manubrium (above the mouth), or the gonads of hydromedusae. In a process known as strobilation, the polyp's tentacles are reabsorbed and the body starts to narrow, forming transverse constrictions, in several places near the upper extremity of the polyp. These deepen as the constriction sites migrate down the body, and separate segments known as ephyra detach. These are free-swimming precursors of the adult medusa stage, which is the life stage that is typically identified as a jellyfish. The ephyrae, usually only a millimeter or two across initially, swim away from the polyp and grow. Limnomedusae polyps can asexually produce a creeping frustule larval form, which crawls away before developing into another polyp. A few species can produce new medusae by budding directly from the medusan stage. Some hydromedusae reproduce by fission.
Lifespan
Little is known of the life histories of many jellyfish as the places on the seabed where the benthic forms of those species live have not been found. However, an asexually reproducing strobila form can sometimes live for several years, producing new medusae (ephyra larvae) each year.
An unusual species, Turritopsis dohrnii, formerly classified as Turritopsis nutricula, might be effectively immortal because of its ability under certain circumstances to transform from medusa back to the polyp stage, thereby escaping the death that typically awaits medusae post-reproduction if they have not otherwise been eaten by some other organism. So far this reversal has been observed only in the laboratory.
Locomotion
Jellyfish locomotion is highly efficient. Muscles in the jellylike bell contract, setting up a start vortex and propelling the animal. When the contraction ends, the bell recoils elastically, creating a stop vortex with no extra energy input.
Using the moon jelly Aurelia aurita as an example, jellyfish have been shown to be the most energy-efficient swimmers of all animals. They move through the water by radially expanding and contracting their bell-shaped bodies to push water behind them. They pause between the contraction and expansion phases to create two vortex rings. Muscles are used for the contraction of the body, which creates the first vortex and pushes the animal forward, but the mesoglea is so elastic that the expansion is powered exclusively by relaxing the bell, which releases the energy stored from the contraction. Meanwhile, the second vortex ring starts to spin faster, sucking water into the bell and pushing against the centre of the body, giving a secondary and "free" boost forward. The mechanism, called passive energy recapture, only works in relatively small jellyfish moving at low speeds, allowing the animal to travel 30 percent farther on each swimming cycle. Jellyfish achieved a 48 percent lower cost of transport (food and oxygen intake versus energy spent in movement) than other animals in similar studies. One reason for this is that most of the gelatinous tissue of the bell is inactive, using no energy during swimming.
Ecology
Diet
Jellyfish are, like other cnidarians, generally carnivorous (or parasitic), feeding on planktonic organisms, crustaceans, small fish, fish eggs and larvae, and other jellyfish, ingesting food and voiding undigested waste through the mouth. They hunt passively using their tentacles as drift lines, or sink through the water with their tentacles spread widely; the tentacles, which contain nematocysts to stun or kill the prey, may then flex to help bring it to the mouth. Their swimming technique also helps them to capture prey; when their bell expands it sucks in water which brings more potential prey within reach of the tentacles.
A few species such as Aglaura hemistoma are omnivorous, feeding on microplankton which is a mixture of zooplankton and phytoplankton (microscopic plants) such as dinoflagellates. Others harbour mutualistic algae (Zooxanthellae) in their tissues; the spotted jellyfish (Mastigias papua) is typical of these, deriving part of its nutrition from the products of photosynthesis, and part from captured zooplankton. The upside-down jellyfish (Cassiopea andromeda) also has a symbiotic relationship with microalgae, but captures tiny animals to supplement their diet. This is done by releasing tiny balls of living cells composed of mesoglea. These use cilia to drive them through water and stinging cells which stun the prey. The blobs also seems to have digestive capabilities.
Predation
Other species of jellyfish are among the most common and important jellyfish predators. Sea anemones may eat jellyfish that drift into their range. Other predators include tunas, sharks, swordfish, sea turtles and penguins. Jellyfish washed up on the beach are consumed by foxes, other terrestrial mammals and birds. In general however, few animals prey on jellyfish; they can broadly be considered to be top predators in the food chain. Once jellyfish have become dominant in an ecosystem, for example through overfishing which removes predators of jellyfish larvae, there may be no obvious way for the previous balance to be restored: they eat fish eggs and juvenile fish, and compete with fish for food, preventing fish stocks from recovering.
Symbiosis
Some small fish are immune to the stings of the jellyfish and live among the tentacles, serving as bait in a fish trap; they are safe from potential predators and are able to share the fish caught by the jellyfish. The cannonball jellyfish has a symbiotic relationship with ten different species of fish, and with the longnose spider crab, which lives inside the bell, sharing the jellyfish's food and nibbling its tissues.
Main article: Jellyfish bloom
Jellyfish form large masses or blooms in certain environmental conditions of ocean currents, nutrients, sunshine, temperature, season, prey availability, reduced predation and oxygen concentration. Currents collect jellyfish together, especially in years with unusually high populations. Jellyfish can detect marine currents and swim against the current to congregate in blooms. Jellyfish are better able to survive in nutrient-rich, oxygen-poor water than competitors, and thus can feast on plankton without competition. Jellyfish may also benefit from saltier waters, as saltier waters contain more iodine, which is necessary for polyps to turn into jellyfish. Rising sea temperatures caused by climate change may also contribute to jellyfish blooms, because many species of jellyfish are able to survive in warmer waters. Increased nutrients from agricultural or urban runoff with nutrients including nitrogen and phosphorus compounds increase the growth of phytoplankton, causing eutrophication and algal blooms. When the phytoplankton die, they may create dead zones, so-called because they are hypoxic (low in oxygen). This in turn kills fish and other animals, but not jellyfish, allowing them to bloom. Jellyfish populations may be expanding globally as a result of land runoff and overfishing of their natural predators. Jellyfish are well placed to benefit from disturbance of marine ecosystems. They reproduce rapidly; they prey upon many species, while few species prey on them; and they feed via touch rather than visually, so they can feed effectively at night and in turbid waters. It may be difficult for fish stocks to re-establish themselves in marine ecosystems once they have become dominated by jellyfish, because jellyfish feed on plankton, which includes fish eggs and larvae.
As suspected at the turn of this century, jellyfish blooms are increasing in frequency. Between 2013 and 2020 the Mediterranean Science Commission monitored on a weekly basis the frequency of such outbreaks in coastal waters from Morocco to the Black Sea, revealing a relatively high frequency of these blooms nearly all year round, with peaks observed from March to July and often again in the autumn. The blooms are caused by different jellyfish species, depending on their localisation within the Basin: one observes a clear dominance of Pelagia noctiluca and Velella velella outbreaks in the western Mediterranean, of Rhizostoma pulmo and Rhopilema nomadica outbreaks in the eastern Mediterranean, and of Aurelia aurita and Mnemiopsis leidyi outbreaks in the Black Sea.
Some jellyfish populations that have shown clear increases in the past few decades are invasive species, newly arrived from other habitats: examples include the Black Sea, Caspian Sea, Baltic Sea, central and eastern Mediterranean, Hawaii, and tropical and subtropical parts of the West Atlantic (including the Caribbean, Gulf of Mexico and Brazil).
Jellyfish blooms can have significant impact on community structure. Some carnivorous jellyfish species prey on zooplankton while others graze on primary producers. Reductions in zooplankton and ichthyoplankton due to a jellyfish bloom can ripple through the trophic levels. High-density jellyfish populations can outcompete other predators and reduce fish recruitment. Increased grazing on primary producers by jellyfish can also interrupt energy transfer to higher trophic levels.
During blooms, jellyfish significantly alter the nutrient availability in their environment. Blooms require large amounts of available organic nutrients in the water column to grow, limiting availability for other organisms. Some jellyfish have a symbiotic relationship with single-celled dinoflagellates, allowing them to assimilate inorganic carbon, phosphorus, and nitrogen creating competition for phytoplankton. Their large biomass makes them an important source of dissolved and particulate organic matter for microbial communities through excretion, mucus production, and decomposition. The microbes break down the organic matter into inorganic ammonium and phosphate. However, the low carbon availability shifts the process from production to respiration creating low oxygen areas making the dissolved inorganic nitrogen and phosphorus largely unavailable for primary production.
These blooms have very real impacts on industries. Jellyfish can outcompete fish by utilizing open niches in over-fished fisheries. Catch of jellyfish can strain fishing gear and lead to expenses relating to damaged gear. Power plants have been shut down due to jellyfish blocking the flow of cooling water. Blooms have also been harmful for tourism, causing a rise in stings and sometimes the closure of beaches.
Jellyfish form a component of jelly-falls, events where gelatinous zooplankton fall to the seafloor, providing food for the benthic organisms there. In temperate and subpolar regions, jelly-falls usually follow immediately after a bloom.
Habitats
Most jellyfish are marine animals, although a few hydromedusae inhabit freshwater. The best known freshwater example is the cosmopolitan hydrozoan jellyfish, Craspedacusta sowerbii. It is less than an inch (2.5 cm) in diameter, colorless and does not sting. Some jellyfish populations have become restricted to coastal saltwater lakes, such as Jellyfish Lake in Palau. Jellyfish Lake is a marine lake where millions of golden jellyfish (Mastigias spp.) migrate horizontally across the lake daily.
Although most jellyfish live well off the ocean floor and form part of the plankton, a few species are closely associated with the bottom for much of their lives and can be considered benthic. The upside-down jellyfish in the genus Cassiopea typically lie on the bottom of shallow lagoons where they sometimes pulsate gently with their umbrella top facing down. Even some deep-sea species of hydromedusae and scyphomedusae are usually collected on or near the bottom. All of the stauromedusae are found attached to either seaweed or rocky or other firm material on the bottom.
Some species explicitly adapt to tidal flux. In Roscoe Bay, jellyfish ride the current at ebb tide until they hit a gravel bar, and then descend below the current. They remain in still waters until the tide rises, ascending and allowing it to sweep them back into the bay. They also actively avoid fresh water from mountain snowmelt, diving until they find enough salt.
Parasites
Jellyfish are hosts to a wide variety of parasitic organisms. They act as intermediate hosts of endoparasitic helminths, with the infection being transferred to the definitive host fish after predation. Some digenean trematodes, especially species in the family Lepocreadiidae, use jellyfish as their second intermediate hosts. Fish become infected by the trematodes when they feed on infected jellyfish.
Relation to humans
Jellyfish have long been eaten in some parts of the world. Fisheries have begun harvesting the American cannonball jellyfish, Stomolophus meleagris, along the southern Atlantic coast of the United States and in the Gulf of Mexico for export to Asia.
Jellyfish are also harvested for their collagen, which is being investigated for use in a variety of applications including the treatment of rheumatoid arthritis.
Aquaculture and fisheries of other species often suffer severe losses – and so losses of productivity – due to jellyfish.
Products
Main article: Jellyfish as food
In some countries, including China, Japan, and Korea, jellyfish are a delicacy. The jellyfish is dried to prevent spoiling. Only some 12 species of scyphozoan jellyfish belonging to the order Rhizostomeae are harvested for food, mostly in southeast Asia. Rhizostomes, especially Rhopilema esculentum in China (海蜇 hǎizhé, 'sea stingers') and Stomolophus meleagris (cannonball jellyfish) in the United States, are favored because of their larger and more rigid bodies and because their toxins are harmless to humans.
Traditional processing methods, carried out by a jellyfish master, involve a 20- to 40-day multi-phase procedure in which, after removing the gonads and mucous membranes, the umbrella and oral arms are treated with a mixture of table salt and alum, and compressed. Processing makes the jellyfish drier and more acidic, producing a crisp texture. Jellyfish prepared this way retain 7–10% of their original weight, and the processed product consists of approximately 94% water and 6% protein. Freshly processed jellyfish has a white, creamy color and turns yellow or brown during prolonged storage.
In China, processed jellyfish are desalted by soaking in water overnight and eaten cooked or raw. The dish is often served shredded with a dressing of oil, soy sauce, vinegar and sugar, or as a salad with vegetables. In Japan, cured jellyfish are rinsed, cut into strips and served with vinegar as an appetizer. Desalted, ready-to-eat products are also available.
Biotechnology
The hydromedusa Aequorea victoria was the source of green fluorescent protein, studied for its role in bioluminescence and later for use as a marker in genetic engineering.
Pliny the Elder reported in his Natural History that the slime of the jellyfish "Pulmo marinus" produced light when rubbed on a walking stick.
In 1961, Osamu Shimomura extracted green fluorescent protein (GFP) and another bioluminescent protein, called aequorin, from the large and abundant hydromedusa Aequorea victoria, while studying photoproteins that cause bioluminescence in this species. Three decades later, Douglas Prasher sequenced and cloned the gene for GFP. Martin Chalfie figured out how to use GFP as a fluorescent marker of genes inserted into other cells or organisms. Roger Tsien later chemically manipulated GFP to produce other fluorescent colors to use as markers. In 2008, Shimomura, Chalfie and Tsien won the Nobel Prize in Chemistry for their work with GFP. Man-made GFP became widely used as a fluorescent tag to show which cells or tissues express specific genes. The genetic engineering technique fuses the gene of interest to the GFP gene. The fused DNA is then put into a cell, to generate either a cell line or (via IVF techniques) an entire animal bearing the gene. In the cell or animal, the artificial gene turns on in the same tissues and the same time as the normal gene, making a fusion of the normal protein with GFP attached to the end, illuminating the animal or cell reveals what tissues express that protein—or at what stage of development. The fluorescence shows where the gene is expressed.
Aquarium display
Jellyfish are displayed in many public aquariums. Often the tank's background is blue and the animals are illuminated by side light, increasing the contrast between the animal and the background. In natural conditions, many jellies are so transparent that they are nearly invisible. Jellyfish are not adapted to closed spaces. They depend on currents to transport them from place to place. Professional exhibits as in the Monterey Bay Aquarium feature precise water flows, typically in circular tanks to avoid trapping specimens in corners. The outflow is spread out over a large surface area and the inflow enters as a sheet of water in front of the outflow, so the jellyfish do not get sucked into it. As of 2009, jellyfish were becoming popular in home aquariums, where they require similar equipment.
Stings
Jellyfish are armed with nematocysts, a type of specialized stinging cell. Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom, but only some species' venom causes an adverse reaction in humans. In a study published in Communications Biology, researchers found a jellyfish species called Cassiopea xamachana which when triggered will release tiny balls of cells that swim around the jellyfish stinging everything in their path. Researchers described these as "self-propelling microscopic grenades" and named them cassiosomes.
The effects of stings range from mild discomfort to extreme pain and death. Most jellyfish stings are not deadly, but stings of some box jellyfish (Irukandji jellyfish), such as the sea wasp, can be deadly. Stings may cause anaphylaxis (a form of shock), which can be fatal. Jellyfish kill 20 to 40 people a year in the Philippines alone. In 2006 the Spanish Red Cross treated 19,000 stung swimmers along the Costa Brava.
Vinegar (3–10% aqueous acetic acid) may help with box jellyfish stings but not the stings of the Portuguese man o' war. Clearing the area of jelly and tentacles reduces nematocyst firing. Scraping the affected skin, such as with the edge of a credit card, may remove remaining nematocysts. Once the skin has been cleaned of nematocysts, hydrocortisone cream applied locally reduces pain and inflammation. Antihistamines may help to control itching. Immunobased antivenins are used for serious box jellyfish stings.
In Elba Island and Corsica dittrichia viscosa is now used by residents and tourists to heal stings from jellyfish, bees and wasps pressing fresh leaves on the skin with quick results.
Mechanical issues
Jellyfish in large quantities can fill and split fishing nets and crush captured fish. They can clog cooling equipment, having disabled power stations in several countries; jellyfish caused a cascading blackout in the Philippines in 1999, as well as damaging the Diablo Canyon Power Plant in California in 2008. They can also stop desalination plants and ships' engines.
Crawler crane built in minifig scale. Extensible chassis and pneumatically raised boom.
For more pictures visit my MOCPages page.
See also how it works on YouTube.
The plane is at 1:48 as usual, but it is noticeably larger than the earlier WWII planes. This allowed me to add a bunch of features, like the extensible dive brakes which show the dive / torpedo bomber origin of the plane.
A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος anisos, "unequal" and πτερόν pteron, "wing", because the hindwing is broader than the forewing). Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Dragonflies can be mistaken for the related group, damselflies (Zygoptera), which are similar in structure, though usually lighter in build; however, the wings of most dragonflies are held flat and away from the body, while damselflies hold their wings folded at rest, along or above the abdomen. Dragonflies are agile fliers, while damselflies have a weaker, fluttery flight. Many dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. An adult dragonfly's compound eyes have nearly 24,000 ommatidia each.
Fossils of very large dragonfly-like insects, sometimes called griffinflies, are found from 325 million years ago (Mya) in Upper Carboniferous rocks; these had wingspans up to about 750 mm (30 in), but were only distant ancestors, not true dragonflies. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threatens dragonfly populations around the world.
Dragonflies are predators, both in their aquatic nymphs stage (also known as naiads) and as adults. In some species, the nymphal stage lasts for up to five years, and the adult stage may be as long as ten weeks, but most species have an adult lifespan in the order of five weeks or less, and some survive for only a few days. They are fast, agile fliers, sometimes migrating across oceans, and often live near water. They have a uniquely complex mode of reproduction involving indirect insemination, delayed fertilization, and sperm competition. During mating, the male grasps the female at the back of the head, and the female curls her abdomen under her body to pick up sperm from the male's secondary genitalia at the front of his abdomen, forming the "heart" or "wheel" posture.
Dragonflies are represented in human culture on artefacts such as pottery, rock paintings, statues and Art Nouveau jewellery. They are used in traditional medicine in Japan and China, and caught for food in Indonesia. They are symbols of courage, strength, and happiness in Japan, but seen as sinister in European folklore. Their bright colours and agile flight are admired in the poetry of Lord Tennyson and the prose of H. E. Bates.
Evolution
Dragonflies and their relatives are similar in structure to an ancient group, meganisoptera, from the 325 Mya Upper Carboniferous of Europe, a group that included the largest insect that ever lived, Meganeuropsis permiana from the Early Permian, with a wingspan around 750 mm (30 in);. Known informally as "griffinflies", their fossil record ends with the Permian–Triassic extinction event (about 247 Mya). The Protanisoptera, another ancestral group that lacks certain wing vein characters found in modern Odonata, lived from the Early to Late Permian age until the end Permian event, and are known from fossil wings from current-day United States, Russia, and Australia, suggesting they might have been cosmopolitan in distribution. While both of those groups are sometimes referred to as "giant dragonflies", in fact true dragonflies/odonata are more modern insects that had not evolved yet.
Modern dragonflies do retain some traits of their distant predecessors, and are in a group known as palaeoptera, ancient-winged. They, like the gigantic pre-dinosaur griffinflies, lack the ability to fold their wings up against their bodies in the way modern insects do, although some evolved their own different way to do so. The forerunners of modern Odonata are included in a clade called the Panodonata, which include the basal Zygoptera (damselflies) and the Anisoptera (true dragonflies). Today, some 3,000 species are extant around the world.
The relationships of anisopteran families are not fully resolved as of 2013, but all the families are monophyletic except the Corduliidae; the Gomphidae are a sister taxon to all other Anisoptera, the Austropetaliidae are sister to the Aeshnoidea, and the Chlorogomphidae are sister to a clade that includes the Synthemistidae and Libellulidae. On the cladogram, dashed lines indicate unresolved relationships; English names are given (in parentheses)
Distribution and diversity
About 3,012 species of dragonflies were known in 2010; these are classified into 348 genera in 11 families. The distribution of diversity within the biogeographical regions are summarized below (the world numbers are not ordinary totals, as overlaps in species occur).
Dragonflies live on every continent except Antarctica. In contrast to the damselflies (Zygoptera), which tend to have restricted distributions, some genera and species are spread across continents. For example, the blue-eyed darner Rhionaeschna multicolor lives all across North America, and in Central America; emperors Anax live throughout the Americas from as far north as Newfoundland to as far south as Bahia Blanca in Argentina, across Europe to central Asia, North Africa, and the Middle East. The globe skimmer Pantala flavescens is probably the most widespread dragonfly species in the world; it is cosmopolitan, occurring on all continents in the warmer regions. Most Anisoptera species are tropical, with far fewer species in temperate regions.
Some dragonflies, including libellulids and aeshnids, live in desert pools, for example in the Mojave Desert, where they are active in shade temperatures between 18 and 45 °C (64.4 to 113 °F); these insects were able to survive body temperatures above the thermal death point of insects of the same species in cooler places.
Dragonflies live from sea level up to the mountains, decreasing in species diversity with altitude. Their altitudinal limit is about 3700 m, represented by a species of Aeshna in the Pamirs.
Dragonflies become scarce at higher latitudes. They are not native to Iceland, but individuals are occasionally swept in by strong winds, including a Hemianax ephippiger native to North Africa, and an unidentified darter species. In Kamchatka, only a few species of dragonfly including the treeline emerald Somatochlora arctica and some aeshnids such as Aeshna subarctica are found, possibly because of the low temperature of the lakes there. The treeline emerald also lives in northern Alaska, within the Arctic Circle, making it the most northerly of all dragonflies.
General description
Dragonflies (suborder Anisoptera) are heavy-bodied, strong-flying insects that hold their wings horizontally both in flight and at rest. By contrast, damselflies (suborder Zygoptera) have slender bodies and fly more weakly; most species fold their wings over the abdomen when stationary, and the eyes are well separated on the sides of the head.
An adult dragonfly has three distinct segments, the head, thorax, and abdomen, as in all insects. It has a chitinous exoskeleton of hard plates held together with flexible membranes. The head is large with very short antennae. It is dominated by the two compound eyes, which cover most of its surface. The compound eyes are made up of ommatidia, the numbers being greater in the larger species. Aeshna interrupta has 22650 ommatidia of two varying sizes, 4500 being large. The facets facing downward tend to be smaller. Petalura gigantea has 23890 ommatidia of just one size. These facets provide complete vision in the frontal hemisphere of the dragonfly. The compound eyes meet at the top of the head (except in the Petaluridae and Gomphidae, as also in the genus Epiophlebia). Also, they have three simple eyes or ocelli. The mouthparts are adapted for biting with a toothed jaw; the flap-like labrum, at the front of the mouth, can be shot rapidly forward to catch prey. The head has a system for locking it in place that consists of muscles and small hairs on the back of the head that grip structures on the front of the first thoracic segment. This arrester system is unique to the Odonata, and is activated when feeding and during tandem flight.
The thorax consists of three segments as in all insects. The prothorax is small and is flattened dorsally into a shield-like disc, which has two transverse ridges. The mesothorax and metathorax are fused into a rigid, box-like structure with internal bracing, and provide a robust attachment for the powerful wing muscles inside. The thorax bears two pairs of wings and three pairs of legs. The wings are long, veined, and membranous, narrower at the tip and wider at the base. The hindwings are broader than the forewings and the venation is different at the base. The veins carry haemolymph, which is analogous to blood in vertebrates, and carries out many similar functions, but which also serves a hydraulic function to expand the body between nymphal stages (instars) and to expand and stiffen the wings after the adult emerges from the final nymphal stage. The leading edge of each wing has a node where other veins join the marginal vein, and the wing is able to flex at this point. In most large species of dragonflies, the wings of females are shorter and broader than those of males. The legs are rarely used for walking, but are used to catch and hold prey, for perching, and for climbing on plants. Each has two short basal joints, two long joints, and a three-jointed foot, armed with a pair of claws. The long leg joints bear rows of spines, and in males, one row of spines on each front leg is modified to form an "eyebrush", for cleaning the surface of the compound eye.
The abdomen is long and slender and consists of 10 segments. Three terminal appendages are on segment 10; a pair of superiors (claspers) and an inferior. The second and third segments are enlarged, and in males, on the underside of the second segment has a cleft, forming the secondary genitalia consisting of the lamina, hamule, genital lobe, and penis. There are remarkable variations in the presence and the form of the penis and the related structures, the flagellum, cornua, and genital lobes. Sperm is produced at the 9th segment, and is transferred to the secondary genitalia prior to mating. The male holds the female behind the head using a pair of claspers on the terminal segment. In females, the genital opening is on the underside of the eighth segment, and is covered by a simple flap (vulvar lamina) or an ovipositor, depending on species and the method of egg-laying. Dragonflies having simple flaps shed the eggs in water, mostly in flight. Dragonflies having ovipositors use them to puncture soft tissues of plants and place the eggs singly in each puncture they make.
Dragonfly nymphs vary in form with species, and are loosely classed into claspers, sprawlers, hiders, and burrowers. The first instar is known as a prolarva, a relatively inactive stage from which it quickly moults into the more active nymphal form. The general body plan is similar to that of an adult, but the nymph lacks wings and reproductive organs. The lower jaw has a huge, extensible labium, armed with hooks and spines, which is used for catching prey. This labium is folded under the body at rest and struck out at great speed by hydraulic pressure created by the abdominal muscles. Whereas damselfly nymphs have three feathery external gills, dragonfly nymphs have internal gills, located around the fourth and fifth abdominal segments. Water is pumped in and out of the abdomen through an opening at the tip. The naiads of some clubtails (Gomphidae) that burrow into the sediment, have a snorkel-like tube at the end of the abdomen enabling them to draw in clean water while they are buried in mud. Naiads can forcefully expel a jet of water to propel themselves with great rapidity.
Colouration
Many adult dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. Their overall colouration is often a combination of yellow, red, brown, and black pigments, with structural colours. Blues are typically created by microstructures in the cuticle that reflect blue light. Greens often combine a structural blue with a yellow pigment. Freshly emerged adults, known as tenerals, are often pale-coloured and obtain their typical colours after a few days, some have their bodies covered with a pale blue, waxy powderiness called pruinosity; it wears off when scraped during mating, leaving darker areas.
Some dragonflies, such as the green darner, Anax junius, have a noniridescent blue that is produced structurally by scatter from arrays of tiny spheres in the endoplasmic reticulum of epidermal cells underneath the cuticle.
The wings of dragonflies are generally clear, apart from the dark veins and pterostigmata. In the chasers (Libellulidae), however, many genera have areas of colour on the wings: for example, groundlings (Brachythemis) have brown bands on all four wings, while some scarlets (Crocothemis) and dropwings (Trithemis) have bright orange patches at the wing bases. Some aeshnids such as the brown hawker (Aeshna grandis) have translucent, pale yellow wings.
Dragonfly nymphs are usually a well-camouflaged blend of dull brown, green, and grey.
Biology
Ecology
Dragonflies and damselflies are predatory both in the aquatic nymphal and adult stages. Nymphs feed on a range of freshwater invertebrates and larger ones can prey on tadpoles and small fish. Adults capture insect prey in the air, making use of their acute vision and highly controlled flight. The mating system of dragonflies is complex, and they are among the few insect groups that have a system of indirect sperm transfer along with sperm storage, delayed fertilization, and sperm competition.
Adult males vigorously defend territories near water; these areas provide suitable habitat for the nymphs to develop, and for females to lay their eggs. Swarms of feeding adults aggregate to prey on swarming prey such as emerging flying ants or termites.
Dragonflies as a group occupy a considerable variety of habitats, but many species, and some families, have their own specific environmental requirements. Some species prefer flowing waters, while others prefer standing water. For example, the Gomphidae (clubtails) live in running water, and the Libellulidae (skimmers) live in still water. Some species live in temporary water pools and are capable of tolerating changes in water level, desiccation, and the resulting variations in temperature, but some genera such as Sympetrum (darters) have eggs and nymphs that can resist drought and are stimulated to grow rapidly in warm, shallow pools, also often benefiting from the absence of predators there. Vegetation and its characteristics including submerged, floating, emergent, or waterside are also important. Adults may require emergent or waterside plants to use as perches; others may need specific submerged or floating plants on which to lay eggs. Requirements may be highly specific, as in Aeshna viridis (green hawker), which lives in swamps with the water-soldier, Stratiotes aloides. The chemistry of the water, including its trophic status (degree of enrichment with nutrients) and pH can also affect its use by dragonflies. Most species need moderate conditions, not too eutrophic, not too acidic; a few species such as Sympetrum danae (black darter) and Libellula quadrimaculata (four-spotted chaser) prefer acidic waters such as peat bogs, while others such as Libellula fulva (scarce chaser) need slow-moving, eutrophic waters with reeds or similar waterside plants.
Behaviour
Many dragonflies, particularly males, are territorial. Some defend a territory against others of their own species, some against other species of dragonfly and a few against insects in unrelated groups. A particular perch may give a dragonfly a good view over an insect-rich feeding ground; males of many species such as the Pachydiplax longipennis (blue dasher) jostle other dragonflies to maintain the right to alight there. Defending a breeding territory is common among male dragonflies, especially in species that congregate around ponds. The territory contains desirable features such as a sunlit stretch of shallow water, a special plant species, or the preferred substrate for egg-laying. The territory may be small or large, depending on its quality, the time of day, and the number of competitors, and may be held for a few minutes or several hours. Dragonflies including Tramea lacerata (black saddlebags) may notice landmarks that assist in defining the boundaries of the territory. Landmarks may reduce the costs of territory establishment, or might serve as a spatial reference. Some dragonflies signal ownership with striking colours on the face, abdomen, legs, or wings. The Plathemis lydia (common whitetail) dashes towards an intruder holding its white abdomen aloft like a flag. Other dragonflies engage in aerial dogfights or high-speed chases. A female must mate with the territory holder before laying her eggs. There is also conflict between the males and females. Females may sometimes be harassed by males to the extent that it affects their normal activities including foraging and in some dimorphic species females have evolved multiple forms with some forms appearing deceptively like males. In some species females have evolved behavioural responses such as feigning death to escape the attention of males. Similarly, selection of habitat by adult dragonflies is not random, and terrestrial habitat patches may be held for up to 3 months. A species tightly linked to its birth site utilises a foraging area that is several orders of magnitude larger than the birth site.
Reproduction
Mating in dragonflies is a complex, precisely choreographed process. First, the male has to attract a female to his territory, continually driving off rival males. When he is ready to mate, he transfers a packet of sperm from his primary genital opening on segment 9, near the end of his abdomen, to his secondary genitalia on segments 2–3, near the base of his abdomen. The male then grasps the female by the head with the claspers at the end of his abdomen; the structure of the claspers varies between species, and may help to prevent interspecific mating. The pair flies in tandem with the male in front, typically perching on a twig or plant stem. The female then curls her abdomen downwards and forwards under her body to pick up the sperm from the male's secondary genitalia, while the male uses his "tail" claspers to grip the female behind the head: this distinctive posture is called the "heart" or "wheel"; the pair may also be described as being "in cop".
Egg-laying (ovipositing) involves not only the female darting over floating or waterside vegetation to deposit eggs on a suitable substrate, but also the male hovering above her or continuing to clasp her and flying in tandem. The male attempts to prevent rivals from removing his sperm and inserting their own, something made possible by delayed fertilisation and driven by sexual selection. If successful, a rival male uses his penis to compress or scrape out the sperm inserted previously; this activity takes up much of the time that a copulating pair remains in the heart posture. Flying in tandem has the advantage that less effort is needed by the female for flight and more can be expended on egg-laying, and when the female submerges to deposit eggs, the male may help to pull her out of the water.
Egg-laying takes two different forms depending on the species. The female in some families has a sharp-edged ovipositor with which she slits open a stem or leaf of a plant on or near the water, so she can push her eggs inside. In other families such as clubtails (Gomphidae), cruisers (Macromiidae), emeralds (Corduliidae), and skimmers (Libellulidae), the female lays eggs by tapping the surface of the water repeatedly with her abdomen, by shaking the eggs out of her abdomen as she flies along, or by placing the eggs on vegetation. In a few species, the eggs are laid on emergent plants above the water, and development is delayed until these have withered and become immersed.
Life cycle
Dragonflies are hemimetabolous insects; they do not have a pupal stage and undergo an incomplete metamorphosis with a series of nymphal stages from which the adult emerges. Eggs laid inside plant tissues are usually shaped like grains of rice, while other eggs are the size of a pinhead, ellipsoidal, or nearly spherical. A clutch may have as many as 1500 eggs, and they take about a week to hatch into aquatic nymphs or naiads which moult between six and 15 times (depending on species) as they grow. Most of a dragonfly's life is spent as a nymph, beneath the water's surface. The nymph extends its hinged labium (a toothed mouthpart similar to a lower mandible, which is sometimes termed as a "mask" as it is normally folded and held before the face) that can extend forward and retract rapidly to capture prey such as mosquito larvae, tadpoles, and small fish. They breathe through gills in their rectum, and can rapidly propel themselves by suddenly expelling water through the anus. Some naiads, such as the later stages of Antipodophlebia asthenes, hunt on land.
The nymph stage of dragonflies lasts up to five years in large species, and between two months and three years in smaller species. When the naiad is ready to metamorphose into an adult, it stops feeding and makes its way to the surface, generally at night. It remains stationary with its head out of the water, while its respiration system adapts to breathing air, then climbs up a reed or other emergent plant, and moults (ecdysis). Anchoring itself firmly in a vertical position with its claws, its skin begins to split at a weak spot behind the head. The adult dragonfly crawls out of its nymph skin, the exuvia, arching backwards when all but the tip of its abdomen is free, to allow its exoskeleton to harden. Curling back upwards, it completes its emergence, swallowing air, which plumps out its body, and pumping haemolymph into its wings, which causes them to expand to their full extent.
Dragonflies in temperate areas can be categorized into two groups, an early group and a later one. In any one area, individuals of a particular "spring species" emerge within a few days of each other. The springtime darner (Basiaeschna janata), for example, is suddenly very common in the spring, but disappears a few weeks later and is not seen again until the following year. By contrast, a "summer species" emerges over a period of weeks or months, later in the year. They may be seen on the wing for several months, but this may represent a whole series of individuals, with new adults hatching out as earlier ones complete their lifespans.
Sex ratios
The sex ratio of male to female dragonflies varies both temporally and spatially. Adult dragonflies have a high male-biased ratio at breeding habitats. The male-bias ratio has contributed partially to the females using different habitats to avoid male harassment. As seen in Hine's emerald dragonfly (Somatochlora hineana), male populations use wetland habitats, while females use dry meadows and marginal breeding habitats, only migrating to the wetlands to lay their eggs or to find mating partners. Unwanted mating is energetically costly for females because it affects the amount of time that they are able to spend foraging.
Flight
Dragonflies are powerful and agile fliers, capable of migrating across the sea, moving in any direction, and changing direction suddenly. In flight, the adult dragonfly can propel itself in six directions: upward, downward, forward, backward, to left and to right. They have four different styles of flight: A number of flying modes are used that include counter-stroking, with forewings beating 180° out of phase with the hindwings, is used for hovering and slow flight. This style is efficient and generates a large amount of lift; phased-stroking, with the hindwings beating 90° ahead of the forewings, is used for fast flight. This style creates more thrust, but less lift than counter-stroking; synchronised-stroking, with forewings and hindwings beating together, is used when changing direction rapidly, as it maximises thrust; and gliding, with the wings held out, is used in three situations: free gliding, for a few seconds in between bursts of powered flight; gliding in the updraft at the crest of a hill, effectively hovering by falling at the same speed as the updraft; and in certain dragonflies such as darters, when "in cop" with a male, the female sometimes simply glides while the male pulls the pair along by beating his wings.
The wings are powered directly, unlike most families of insects, with the flight muscles attached to the wing bases. Dragonflies have a high power/weight ratio, and have been documented accelerating at 4 G linearly and 9 G in sharp turns while pursuing prey.
Dragonflies generate lift in at least four ways at different times, including classical lift like an aircraft wing; supercritical lift with the wing above the critical angle, generating high lift and using very short strokes to avoid stalling; and creating and shedding vortices. Some families appear to use special mechanisms, as for example the Libellulidae which take off rapidly, their wings beginning pointed far forward and twisted almost vertically. Dragonfly wings behave highly dynamically during flight, flexing and twisting during each beat. Among the variables are wing curvature, length and speed of stroke, angle of attack, forward/back position of wing, and phase relative to the other wings.
Flight speed
Old and unreliable claims are made that dragonflies such as the southern giant darner can fly up to 97 km/h (60 mph). However, the greatest reliable flight speed records are for other types of insects. In general, large dragonflies like the hawkers have a maximum speed of 36–54 km/h (22–34 mph) with average cruising speed of about 16 km/h (9.9 mph). Dragonflies can travel at 100 body-lengths per second in forward flight, and three lengths per second backwards.
Motion camouflage
n high-speed territorial battles between male Australian emperors (Hemianax papuensis), the fighting dragonflies adjust their flight paths to appear stationary to their rivals, minimizing the chance of being detected as they approach.[a] To achieve the effect, the attacking dragonfly flies towards his rival, choosing his path to remain on a line between the rival and the start of his attack path. The attacker thus looms larger as he closes on the rival, but does not otherwise appear to move. Researchers found that six of 15 encounters involved motion camouflage.
Temperature control
The flight muscles need to be kept at a suitable temperature for the dragonfly to be able to fly. Being cold-blooded, they can raise their temperature by basking in the sun. Early in the morning, they may choose to perch in a vertical position with the wings outstretched, while in the middle of the day, a horizontal stance may be chosen. Another method of warming up used by some larger dragonflies is wing-whirring, a rapid vibration of the wings that causes heat to be generated in the flight muscles. The green darner (Anax junius) is known for its long-distance migrations, and often resorts to wing-whirring before dawn to enable it to make an early start.
Becoming too hot is another hazard, and a sunny or shady position for perching can be selected according to the ambient temperature. Some species have dark patches on the wings which can provide shade for the body, and a few use the obelisk posture to avoid overheating. This behaviour involves doing a "handstand", perching with the body raised and the abdomen pointing towards the sun, thus minimising the amount of solar radiation received. On a hot day, dragonflies sometimes adjust their body temperature by skimming over a water surface and briefly touching it, often three times in quick succession. This may also help to avoid desiccation.
Feeding
Adult dragonflies hunt on the wing using their exceptionally acute eyesight and strong, agile flight. They are almost exclusively carnivorous, eating a wide variety of insects ranging from small midges and mosquitoes to butterflies, moths, damselflies, and smaller dragonflies. A large prey item is subdued by being bitten on the head and is carried by the legs to a perch. Here, the wings are discarded and the prey usually ingested head first. A dragonfly may consume as much as a fifth of its body weight in prey per day. Dragonflies are also some of the insect world's most efficient hunters, catching up to 95% of the prey they pursue.
The nymphs are voracious predators, eating most living things that are smaller than they are. Their staple diet is mostly bloodworms and other insect larvae, but they also feed on tadpoles and small fish. A few species, especially those that live in temporary waters, are likely to leave the water to feed. Nymphs of Cordulegaster bidentata sometimes hunt small arthropods on the ground at night, while some species in the Anax genus have even been observed leaping out of the water to attack and kill full-grown tree frogs.
Eyesight
Dragonfly vision is thought to be like slow motion for humans. Dragonflies see faster than we do; they see around 200 images per second. A dragonfly can see in 360 degrees, and nearly 80 percent of the insect's brain is dedicated to its sight.
Predators
Although dragonflies are swift and agile fliers, some predators are fast enough to catch them. These include falcons such as the American kestrel, the merlin, and the hobby; nighthawks, swifts, flycatchers and swallows also take some adults; some species of wasps, too, prey on dragonflies, using them to provision their nests, laying an egg on each captured insect. In the water, various species of ducks and herons eat dragonfly nymphs and they are also preyed on by newts, frogs, fish, and water spiders. Amur falcons, which migrate over the Indian Ocean at a period that coincides with the migration of the globe skimmer dragonfly, Pantala flavescens, may actually be feeding on them while on the wing.
Parasites
Dragonflies are affected by three major groups of parasites: water mites, gregarine protozoa, and trematode flatworms (flukes). Water mites, Hydracarina, can kill smaller dragonfly nymphs, and may also be seen on adults. Gregarines infect the gut and may cause blockage and secondary infection. Trematodes are parasites of vertebrates such as frogs, with complex life cycles often involving a period as a stage called a cercaria in a secondary host, a snail. Dragonfly nymphs may swallow cercariae, or these may tunnel through a nymph's body wall; they then enter the gut and form a cyst or metacercaria, which remains in the nymph for the whole of its development. If the nymph is eaten by a frog, the amphibian becomes infected by the adult or fluke stage of the trematode.
Dragonflies and humans
Conservation
Most odonatologists live in temperate areas and the dragonflies of North America and Europe have been the subject of much research. However, the majority of species live in tropical areas and have been little studied. With the destruction of rainforest habitats, many of these species are in danger of becoming extinct before they have even been named. The greatest cause of decline is forest clearance with the consequent drying up of streams and pools which become clogged with silt. The damming of rivers for hydroelectric schemes and the drainage of low-lying land has reduced suitable habitat, as has pollution and the introduction of alien species.
In 1997, the International Union for Conservation of Nature set up a status survey and conservation action plan for dragonflies. This proposes the establishment of protected areas around the world and the management of these areas to provide suitable habitat for dragonflies. Outside these areas, encouragement should be given to modify forestry, agricultural, and industrial practices to enhance conservation. At the same time, more research into dragonflies needs to be done, consideration should be given to pollution control and the public should be educated about the importance of biodiversity.
Habitat degradation has reduced dragonfly populations across the world, for example in Japan. Over 60% of Japan's wetlands were lost in the 20th century, so its dragonflies now depend largely on rice fields, ponds, and creeks. Dragonflies feed on pest insects in rice, acting as a natural pest control. Dragonflies are steadily declining in Africa, and represent a conservation priority.
The dragonfly's long lifespan and low population density makes it vulnerable to disturbance, such as from collisions with vehicles on roads built near wetlands. Species that fly low and slow may be most at risk.
Dragonflies are attracted to shiny surfaces that produce polarization which they can mistake for water, and they have been known to aggregate close to polished gravestones, solar panels, automobiles, and other such structures on which they attempt to lay eggs. These can have a local impact on dragonfly populations; methods of reducing the attractiveness of structures such as solar panels are under experimentation.
In culture
A blue-glazed faience dragonfly amulet was found by Flinders Petrie at Lahun, from the Late Middle Kingdom of ancient Egypt.
Many Native American tribes consider dragonflies to be medicine animals that had special powers. For example, the southwestern tribes, including the Pueblo, Hopi, and Zuni, associated dragonflies with transformation. They referred to dragonflies as "snake doctors" because they believed dragonflies followed snakes into the ground and healed them if they were injured. For the Navajo, dragonflies symbolize pure water. Often stylized in a double-barred cross design, dragonflies are a common motif in Zuni pottery, as well as Hopi rock art and Pueblo necklaces.: 20–26
As a seasonal symbol in Japan, the dragonflies are associated with season of autumn. In Japan, they are symbols of rebirth, courage, strength, and happiness. They are also depicted frequently in Japanese art and literature, especially haiku poetry. Japanese children catch large dragonflies as a game, using a hair with a small pebble tied to each end, which they throw into the air. The dragonfly mistakes the pebbles for prey, gets tangled in the hair, and is dragged to the ground by the weight.: 38
In Chinese culture, dragonflies symbolize both change and instability. They are also symbols in the Chinese practices of Feng Shui, where placements of dragonfly statues and artwork in parts of a home or office are believed to bring new insights and positive changes.
In both China and Japan, dragonflies have been used in traditional medicine. In Indonesia, adult dragonflies are caught on poles made sticky with birdlime, then fried in oil as a delicacy.
Images of dragonflies are common in Art Nouveau, especially in jewellery designs. They have also been used as a decorative motif on fabrics and home furnishings. Douglas, a British motorcycle manufacturer based in Bristol, named its innovatively designed postwar 350-cc flat-twin model the Dragonfly.
Among the classical names of Japan are Akitsukuni (秋津国), Akitsushima (秋津島), Toyo-akitsushima (豊秋津島). Akitsu is an old word for dragonfly, so one interpretation of Akitsushima is "Dragonfly Island". This is attributed to a legend in which Japan's mythical founder, Emperor Jimmu, was bitten by a mosquito, which was then eaten by a dragonfly.
In Europe, dragonflies have often been seen as sinister. Some English vernacular names, such as "horse-stinger", "devil's darning needle", and "ear cutter", link them with evil or injury. Swedish folklore holds that the devil uses dragonflies to weigh people's souls.: 25–27 The Norwegian name for dragonflies is Øyenstikker ("eye-poker"), and in Portugal, they are sometimes called tira-olhos ("eyes-snatcher"). They are often associated with snakes, as in the Welsh name gwas-y-neidr, "adder's servant". The Southern United States terms "snake doctor" and "snake feeder" refer to a folk belief that dragonflies catch insects for snakes or follow snakes around and stitch them back together if they are injured. Interestingly, the Hungarian name for dragonfly is szitakötő ("sieve-knitter").
The watercolourist Moses Harris (1731–1785), known for his The Aurelian or natural history of English insects (1766), published in 1780, the first scientific descriptions of several Odonata including the banded demoiselle, Calopteryx splendens. He was the first English artist to make illustrations of dragonflies accurate enough to be identified to species (Aeshna grandis at top left of plate illustrated), though his rough drawing of a nymph (at lower left) with the mask extended appears to be plagiarised.[b]
More recently, dragonfly watching has become popular in America as some birdwatchers seek new groups to observe.
In heraldry, like other winged insects, the dragonfly is typically depicted tergiant (with its back facing the viewer), with its head to chief.
In poetry and literature
Lafcadio Hearn wrote in his 1901 book A Japanese Miscellany that Japanese poets had created dragonfly haiku "almost as numerous as are the dragonflies themselves in the early autumn." The poet Matsuo Bashō (1644–1694) wrote haiku such as "Crimson pepper pod / add two pairs of wings, and look / darting dragonfly", relating the autumn season to the dragonfly. Hori Bakusui (1718–1783) similarly wrote "Dyed he is with the / Colour of autumnal days, / O red dragonfly."
The poet Lord Tennyson, described a dragonfly splitting its old skin and emerging shining metallic blue like "sapphire mail" in his 1842 poem "The Two Voices", with the lines "An inner impulse rent the veil / Of his old husk: from head to tail / Came out clear plates of sapphire mail."
The novelist H. E. Bates described the rapid, agile flight of dragonflies in his 1937 nonfiction book Down the River:
I saw, once, an endless procession, just over an area of water-lilies, of small sapphire dragonflies, a continuous play of blue gauze over the snowy flowers above the sun-glassy water. It was all confined, in true dragonfly fashion, to one small space. It was a continuous turning and returning, an endless darting, poising, striking and hovering, so swift that it was often lost in sunlight.
In technology
A dragonfly has been genetically modified with light-sensitive "steering neurons" in its nerve cord to create a cyborg-like "DragonflEye". The neurons contain genes like those in the eye to make them sensitive to light. Miniature sensors, a computer chip and a solar panel were fitted in a "backpack" over the insect's thorax in front of its wings. Light is sent down flexible light-pipes named optrodes[c] from the backpack into the nerve cord to give steering commands to the insect. The result is a "micro-aerial vehicle that's smaller, lighter and stealthier than anything else that's manmade".
[Credit: en.wikipedia.org/]
IN ENGLISH BELOW THE LINE
La Ernemann Erni es una càmera de plaques petites i molt senzilla. És de format 4,5x6 cm, tipus caixa i amb un visor de marc extensible. Fou fabricada entre 1924 i 1926.
camerapedia.fandom.com/wiki/Ernemann_Erni
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The Ernemann Erni is a small and very simple plate camera. It is 4.5x6 cm in size, box type and with an extendable frame viewfinder. It was manufactured between 1924 and 1926.
Jellyfish, also known sea jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.
Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle. The medusa is normally the sexual phase, which produces planula larvae; these then disperse widely and enter a sedentary polyp phase, before reaching sexual maturity.
Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the "true jellyfish") are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal group.
Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomeae order are pressed and salted to remove excess water. Australian researchers have described them as a "perfect food": sustainable and protein-rich but relatively low in food energy.
They are also used in research, where the green fluorescent protein used by some species to cause bioluminescence has been adapted as a fluorescent marker for genes inserted into other cells or organisms.
The stinging cells used by jellyfish to subdue their prey can injure humans. Thousands of swimmers worldwide are stung every year, with effects ranging from mild discomfort to serious injury or even death. When conditions are favourable, jellyfish can form vast swarms, which can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea.
Names
The name jellyfish, in use since 1796, has traditionally been applied to medusae and all similar animals including the comb jellies (ctenophores, another phylum). The term jellies or sea jellies is more recent, having been introduced by public aquaria in an effort to avoid use of the word "fish" with its modern connotation of an animal with a backbone, though shellfish, cuttlefish and starfish are not vertebrates either. In scientific literature, "jelly" and "jellyfish" have been used interchangeably. Many sources refer to only scyphozoans as "true jellyfish".
A group of jellyfish is called a "smack" or a "smuck".
Definition
The term jellyfish broadly corresponds to medusae, that is, a life-cycle stage in the Medusozoa. The American evolutionary biologist Paulyn Cartwright gives the following general definition:
Typically, medusozoan cnidarians have a pelagic, predatory jellyfish stage in their life cycle; staurozoans are the exceptions [as they are stalked].
The Merriam-Webster dictionary defines jellyfish as follows:
A free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells.
Given that jellyfish is a common name, its mapping to biological groups is inexact. Some authorities have called the comb jellies and certain salps jellyfish, though other authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa.
The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with on the following cladogram of the animal kingdom:
Jellyfish are not a clade, as they include most of the Medusozoa, barring some of the Hydrozoa. The medusozoan groups included by authorities are indicated on the following phylogenetic tree by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface; the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish.
Taxonomy
The subphylum Medusozoa includes all cnidarians with a medusa stage in their life cycle. The basic cycle is egg, planula larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, Scyphozoa (large jellyfish), Cubozoa (box jellyfish) and Hydrozoa (small jellyfish), and excludes Anthozoa (corals and sea anemones). This suggests that the medusa form evolved after the polyps. Medusozoans have tetramerous symmetry, with parts in fours or multiples of four.
The four major classes of medusozoan Cnidaria are:
Scyphozoa are sometimes called true jellyfish, though they are no more truly jellyfish than the others listed here. They have tetra-radial symmetry. Most have tentacles around the outer margin of the bowl-shaped bell, and long, oral arms around the mouth in the center of the subumbrella.
Cubozoa (box jellyfish) have a (rounded) box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to scyphozoan jellyfish than either are to the Hydrozoa.
Hydrozoa medusae also have tetra-radial symmetry, nearly always have a velum (diaphragm used in swimming) attached just inside the bell margin, do not have oral arms, but a much smaller central stalk-like structure, the manubrium, with terminal mouth opening, and are distinguished by the absence of cells in the mesoglea. Hydrozoa show great diversity of lifestyle; some species maintain the polyp form for their entire life and do not form medusae at all (such as Hydra, which is hence not considered a jellyfish), and a few are entirely medusal and have no polyp form.
Staurozoa (stalked jellyfish) are characterized by a medusa form that is generally sessile, oriented upside down and with a stalk emerging from the apex of the "calyx" (bell), which attaches to the substrate. At least some Staurozoa also have a polyp form that alternates with the medusoid portion of the life cycle. Until recently, Staurozoa were classified within the Scyphozoa.
There are over 200 species of Scyphozoa, about 50 species of Staurozoa, about 50 species of Cubozoa, and the Hydrozoa includes about 1000–1500 species that produce medusae, but many more species that do not.
Fossil history
Since jellyfish have no hard parts, fossils are rare. The oldest unambiguous fossil of a free-swimming medusa is Burgessomedusa from the mid Cambrian Burgess Shale of Canada, which is likely either a stem group of box jellyfish (Cubozoa) or Acraspeda (the clade including Staurozoa, Cubozoa, and Scyphozoa). Other claimed records from the Cambrian of China and Utah in the United States are uncertain, and possibly represent ctenophores instead.
Anatomy
The main feature of a true jellyfish is the umbrella-shaped bell. This is a hollow structure consisting of a mass of transparent jelly-like matter known as mesoglea, which forms the hydrostatic skeleton of the animal. 95% or more of the mesogloea consists of water, but it also contains collagen and other fibrous proteins, as well as wandering amoebocytes which can engulf debris and bacteria. The mesogloea is bordered by the epidermis on the outside and the gastrodermis on the inside. The edge of the bell is often divided into rounded lobes known as lappets, which allow the bell to flex. In the gaps or niches between the lappets are dangling rudimentary sense organs known as rhopalia, and the margin of the bell often bears tentacles.
Anatomy of a scyphozoan jellyfish
On the underside of the bell is the manubrium, a stalk-like structure hanging down from the centre, with the mouth, which also functions as the anus, at its tip. There are often four oral arms connected to the manubrium, streaming away into the water below. The mouth opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. This is subdivided by four thick septa into a central stomach and four gastric pockets. The four pairs of gonads are attached to the septa, and close to them four septal funnels open to the exterior, perhaps supplying good oxygenation to the gonads. Near the free edges of the septa, gastric filaments extend into the gastric cavity; these are armed with nematocysts and enzyme-producing cells and play a role in subduing and digesting the prey. In some scyphozoans, the gastric cavity is joined to radial canals which branch extensively and may join a marginal ring canal. Cilia in these canals circulate the fluid in a regular direction.
Discharge mechanism of a nematocyst
The box jellyfish is largely similar in structure. It has a squarish, box-like bell. A short pedalium or stalk hangs from each of the four lower corners. One or more long, slender tentacles are attached to each pedalium. The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates, allowing box jellyfish to swim faster than true jellyfish. Hydrozoans are also similar, usually with just four tentacles at the edge of the bell, although many hydrozoans are colonial and may not have a free-living medusal stage. In some species, a non-detachable bud known as a gonophore is formed that contains a gonad but is missing many other medusal features such as tentacles and rhopalia. Stalked jellyfish are attached to a solid surface by a basal disk, and resemble a polyp, the oral end of which has partially developed into a medusa with tentacle-bearing lobes and a central manubrium with four-sided mouth.
Most jellyfish do not have specialized systems for osmoregulation, respiration and circulation, and do not have a central nervous system. Nematocysts, which deliver the sting, are located mostly on the tentacles; true jellyfish also have them around the mouth and stomach. Jellyfish do not need a respiratory system because sufficient oxygen diffuses through the epidermis. They have limited control over their movement, but can navigate with the pulsations of the bell-like body; some species are active swimmers most of the time, while others largely drift. The rhopalia contain rudimentary sense organs which are able to detect light, water-borne vibrations, odour and orientation. A loose network of nerves called a "nerve net" is located in the epidermis. Although traditionally thought not to have a central nervous system, nerve net concentration and ganglion-like structures could be considered to constitute one in most species. A jellyfish detects stimuli, and transmits impulses both throughout the nerve net and around a circular nerve ring, to other nerve cells. The rhopalial ganglia contain pacemaker neurones which control swimming rate and direction.
In many species of jellyfish, the rhopalia include ocelli, light-sensitive organs able to tell light from dark. These are generally pigment spot ocelli, which have some of their cells pigmented. The rhopalia are suspended on stalks with heavy crystals at one end, acting like gyroscopes to orient the eyes skyward. Certain jellyfish look upward at the mangrove canopy while making a daily migration from mangrove swamps into the open lagoon, where they feed, and back again.
Box jellyfish have more advanced vision than the other groups. Each individual has 24 eyes, two of which are capable of seeing colour, and four parallel information processing areas that act in competition, supposedly making them one of the few kinds of animal to have a 360-degree view of its environment.
Box jellyfish eye
The study of jellyfish eye evolution is an intermediary to a better understanding of how visual systems evolved on Earth. Jellyfish exhibit immense variation in visual systems ranging from photoreceptive cell patches seen in simple photoreceptive systems to more derived complex eyes seen in box jellyfish. Major topics of jellyfish visual system research (with an emphasis on box jellyfish) include: the evolution of jellyfish vision from simple to complex visual systems), the eye morphology and molecular structures of box jellyfish (including comparisons to vertebrate eyes), and various uses of vision including task-guided behaviors and niche specialization.
Evolution
Experimental evidence for photosensitivity and photoreception in cnidarians antecedes the mid 1900s, and a rich body of research has since covered evolution of visual systems in jellyfish. Jellyfish visual systems range from simple photoreceptive cells to complex image-forming eyes. More ancestral visual systems incorporate extraocular vision (vision without eyes) that encompass numerous receptors dedicated to single-function behaviors. More derived visual systems comprise perception that is capable of multiple task-guided behaviors.
Although they lack a true brain, cnidarian jellyfish have a "ring" nervous system that plays a significant role in motor and sensory activity. This net of nerves is responsible for muscle contraction and movement and culminates the emergence of photosensitive structures. Across Cnidaria, there is large variation in the systems that underlie photosensitivity. Photosensitive structures range from non-specialized groups of cells, to more "conventional" eyes similar to those of vertebrates. The general evolutionary steps to develop complex vision include (from more ancestral to more derived states): non-directional photoreception, directional photoreception, low-resolution vision, and high-resolution vision. Increased habitat and task complexity has favored the high-resolution visual systems common in derived cnidarians such as box jellyfish.
Basal visual systems observed in various cnidarians exhibit photosensitivity representative of a single task or behavior. Extraocular photoreception (a form of non-directional photoreception), is the most basic form of light sensitivity and guides a variety of behaviors among cnidarians. It can function to regulate circadian rhythm (as seen in eyeless hydrozoans) and other light-guided behaviors responsive to the intensity and spectrum of light. Extraocular photoreception can function additionally in positive phototaxis (in planula larvae of hydrozoans), as well as in avoiding harmful amounts of UV radiation via negative phototaxis. Directional photoreception (the ability to perceive direction of incoming light) allows for more complex phototactic responses to light, and likely evolved by means of membrane stacking. The resulting behavioral responses can range from guided spawning events timed by moonlight to shadow responses for potential predator avoidance. Light-guided behaviors are observed in numerous scyphozoans including the common moon jelly, Aurelia aurita, which migrates in response to changes in ambient light and solar position even though they lack proper eyes.
The low-resolution visual system of box jellyfish is more derived than directional photoreception, and thus box jellyfish vision represents the most basic form of true vision in which multiple directional photoreceptors combine to create the first imaging and spatial resolution. This is different from the high-resolution vision that is observed in camera or compound eyes of vertebrates and cephalopods that rely on focusing optics. Critically, the visual systems of box jellyfish are responsible for guiding multiple tasks or behaviors in contrast to less derived visual systems in other jellyfish that guide single behavioral functions. These behaviors include phototaxis based on sunlight (positive) or shadows (negative), obstacle avoidance, and control of swim-pulse rate.
Box jellyfish possess "proper eyes" (similar to vertebrates) that allow them to inhabit environments that lesser derived medusae cannot. In fact, they are considered the only class in the clade Medusozoa that have behaviors necessitating spatial resolution and genuine vision. However, the lens in their eyes are more functionally similar to cup-eyes exhibited in low-resolution organisms, and have very little to no focusing capability. The lack of the ability to focus is due to the focal length exceeding the distance to the retina, thus generating unfocused images and limiting spatial resolution. The visual system is still sufficient for box jellyfish to produce an image to help with tasks such as object avoidance.
Utility as a model organism
Box jellyfish eyes are a visual system that is sophisticated in numerous ways. These intricacies include the considerable variation within the morphology of box jellyfishes' eyes (including their task/behavior specification), and the molecular makeup of their eyes including: photoreceptors, opsins, lenses, and synapses. The comparison of these attributes to more derived visual systems can allow for a further understanding of how the evolution of more derived visual systems may have occurred, and puts into perspective how box jellyfish can play the role as an evolutionary/developmental model for all visual systems.
Characteristics
Box jellyfish visual systems are both diverse and complex, comprising multiple photosystems. There is likely considerable variation in visual properties between species of box jellyfish given the significant inter-species morphological and physiological variation. Eyes tend to differ in size and shape, along with number of receptors (including opsins), and physiology across species of box jellyfish.
Box jellyfish have a series of intricate lensed eyes that are similar to those of more derived multicellular organisms such as vertebrates. Their 24 eyes fit into four different morphological categories. These categories consist of two large, morphologically different medial eyes (a lower and upper lensed eye) containing spherical lenses, a lateral pair of pigment slit eyes, and a lateral pair of pigment pit eyes. The eyes are situated on rhopalia (small sensory structures) which serve sensory functions of the box jellyfish and arise from the cavities of the exumbrella (the surface of the body) on the side of the bells of the jellyfish. The two large eyes are located on the mid-line of the club and are considered complex because they contain lenses. The four remaining eyes lie laterally on either side of each rhopalia and are considered simple. The simple eyes are observed as small invaginated cups of epithelium that have developed pigmentation. The larger of the complex eyes contains a cellular cornea created by a mono ciliated epithelium, cellular lens, homogenous capsule to the lens, vitreous body with prismatic elements, and a retina of pigmented cells. The smaller of the complex eyes is said to be slightly less complex given that it lacks a capsule but otherwise contains the same structure as the larger eye.
Box jellyfish have multiple photosystems that comprise different sets of eyes. Evidence includes immunocytochemical and molecular data that show photopigment differences among the different morphological eye types, and physiological experiments done on box jellyfish to suggest behavioral differences among photosystems. Each individual eye type constitutes photosystems that work collectively to control visually guided behaviors.
Box jellyfish eyes primarily use c-PRCs (ciliary photoreceptor cells) similar to that of vertebrate eyes. These cells undergo phototransduction cascades (process of light absorption by photoreceptors) that are triggered by c-opsins. Available opsin sequences suggest that there are two types of opsins possessed by all cnidarians including an ancient phylogenetic opsin, and a sister ciliary opsin to the c-opsins group. Box jellyfish could have both ciliary and cnidops (cnidarian opsins), which is something not previously believed to appear in the same retina. Nevertheless, it is not entirely evident whether cnidarians possess multiple opsins that are capable of having distinctive spectral sensitivities.
Comparison with other organisms
Comparative research on genetic and molecular makeup of box jellyfishes' eyes versus more derived eyes seen in vertebrates and cephalopods focuses on: lenses and crystallin composition, synapses, and Pax genes and their implied evidence for shared primordial (ancestral) genes in eye evolution.
Box jellyfish eyes are said to be an evolutionary/developmental model of all eyes based on their evolutionary recruitment of crystallins and Pax genes. Research done on box jellyfish including Tripedalia cystophora has suggested that they possess a single Pax gene, PaxB. PaxB functions by binding to crystallin promoters and activating them. PaxB in situ hybridization resulted in PaxB expression in the lens, retina, and statocysts. These results and the rejection of the prior hypothesis that Pax6 was an ancestral Pax gene in eyes has led to the conclusion that PaxB was a primordial gene in eye evolution, and that the eyes of all organisms likely share a common ancestor.
The lens structure of box jellyfish appears very similar to those of other organisms, but the crystallins are distinct in both function and appearance. Weak reactions were seen within the sera and there were very weak sequence similarities within the crystallins among vertebrate and invertebrate lenses. This is likely due to differences in lower molecular weight proteins and the subsequent lack of immunological reactions with antisera that other organisms' lenses exhibit.
All four of the visual systems of box jellyfish species investigated with detail (Carybdea marsupialis, Chiropsalmus quadrumanus, Tamoya haplonema and Tripedalia cystophora) have invaginated synapses, but only in the upper and lower lensed eyes. Different densities were found between the upper and lower lenses, and between species. Four types of chemical synapses have been discovered within the rhopalia which could help in understanding neural organization including: clear unidirectional, dense-core unidirectional, clear bidirectional, and clear and dense-core bidirectional. The synapses of the lensed eyes could be useful as markers to learn more about the neural circuit in box jellyfish retinal areas.
Evolution as a response to natural stimuli
The primary adaptive responses to environmental variation observed in box jellyfish eyes include pupillary constriction speeds in response to light environments, as well as photoreceptor tuning and lens adaptations to better respond to shifts between light environments and darkness. Interestingly, some box jellyfish species' eyes appear to have evolved more focused vision in response to their habitat.
Pupillary contraction appears to have evolved in response to variation in the light environment across ecological niches across three species of box jellyfish (Chironex fleckeri, Chiropsella bronzie, and Carukia barnesi). Behavioral studies suggest that faster pupil contraction rates allow for greater object avoidance, and in fact, species with more complex habitats exhibit faster rates. Ch. bronzie inhabit shallow beach fronts that have low visibility and very few obstacles, thus, faster pupil contraction in response to objects in their environment is not important. Ca. barnesi and Ch. fleckeri are found in more three-dimensionally complex environments like mangroves with an abundance of natural obstacles, where faster pupil contraction is more adaptive. Behavioral studies support the idea that faster pupillary contraction rates assist with obstacle avoidance as well as depth adjustments in response to differing light intensities.
Light/dark adaptation via pupillary light reflexes is an additional form of an evolutionary response to the light environment. This relates to the pupil's response to shifts between light intensity (generally from sunlight to darkness). In the process of light/dark adaptation, the upper and lower lens eyes of different box jellyfish species vary in specific function. The lower lens-eyes contain pigmented photoreceptors and long pigment cells with dark pigments that migrate on light/dark adaptation, while the upper-lens eyes play a concentrated role in light direction and phototaxis given that they face upward towards the water surface (towards the sun or moon). The upper lens of Ch. bronzie does not exhibit any considerable optical power while Tr. cystophora (a box jellyfish species that tends to live in mangroves) does. The ability to use light to visually guide behavior is not of as much importance to Ch. bronzie as it is to species in more obstacle-filled environments. Differences in visually guided behavior serve as evidence that species that share the same number and structure of eyes can exhibit differences in how they control behavior.
Largest and smallest
Jellyfish range from about one millimeter in bell height and diameter, to nearly 2 metres (6+1⁄2 ft) in bell height and diameter; the tentacles and mouth parts usually extend beyond this bell dimension.
The smallest jellyfish are the peculiar creeping jellyfish in the genera Staurocladia and Eleutheria, which have bell disks from 0.5 millimetres (1⁄32 in) to a few millimeters in diameter, with short tentacles that extend out beyond this, which these jellyfish use to move across the surface of seaweed or the bottoms of rocky pools; many of these tiny creeping jellyfish cannot be seen in the field without a hand lens or microscope. They can reproduce asexually by fission (splitting in half). Other very small jellyfish, which have bells about one millimeter, are the hydromedusae of many species that have just been released from their parent polyps; some of these live only a few minutes before shedding their gametes in the plankton and then dying, while others will grow in the plankton for weeks or months. The hydromedusae Cladonema radiatum and Cladonema californicum are also very small, living for months, yet never growing beyond a few mm in bell height and diameter.
The lion's mane jellyfish, Cyanea capillata, was long-cited as the largest jellyfish, and arguably the longest animal in the world, with fine, thread-like tentacles that may extend up to 36.5 m (119 ft 9 in) long (though most are nowhere near that large). They have a moderately painful, but rarely fatal, sting. The increasingly common giant Nomura's jellyfish, Nemopilema nomurai, found in some, but not all years in the waters of Japan, Korea and China in summer and autumn is another candidate for "largest jellyfish", in terms of diameter and weight, since the largest Nomura's jellyfish in late autumn can reach 2 m (6 ft 7 in) in bell (body) diameter and about 200 kg (440 lb) in weight, with average specimens frequently reaching 0.9 m (2 ft 11 in) in bell diameter and about 150 kg (330 lb) in weight. The large bell mass of the giant Nomura's jellyfish can dwarf a diver and is nearly always much greater than the Lion's Mane, whose bell diameter can reach 1 m (3 ft 3 in).
The rarely encountered deep-sea jellyfish Stygiomedusa gigantea is another candidate for "largest jellyfish", with its thick, massive bell up to 100 cm (3 ft 3 in) wide, and four thick, "strap-like" oral arms extending up to 6 m (19+1⁄2 ft) in length, very different from the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane.
Desmonema glaciale, which lives in the Antarctic region, can reach a very large size (several meters). Purple-striped jelly (Chrysaora colorata) can also be extremely long (up to 15 feet).
Life history and behavior
Life cycle
Jellyfish have a complex life cycle which includes both sexual and asexual phases, with the medusa being the sexual stage in most instances. Sperm fertilize eggs, which develop into larval planulae, become polyps, bud into ephyrae and then transform into adult medusae. In some species certain stages may be skipped.
Upon reaching adult size, jellyfish spawn regularly if there is a sufficient supply of food. In most species, spawning is controlled by light, with all individuals spawning at about the same time of day; in many instances this is at dawn or dusk. Jellyfish are usually either male or female (with occasional hermaphrodites). In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae. In a few species, the sperm swim into the female's mouth, fertilizing the eggs within her body, where they remain during early development stages. In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae.
The planula is a small larva covered with cilia. When sufficiently developed, it settles onto a firm surface and develops into a polyp. The polyp generally consists of a small stalk topped by a mouth that is ringed by upward-facing tentacles. The polyps resemble those of closely related anthozoans, such as sea anemones and corals. The jellyfish polyp may be sessile, living on the bottom, boat hulls or other substrates, or it may be free-floating or attached to tiny bits of free-living plankton or rarely, fish or other invertebrates. Polyps may be solitary or colonial. Most polyps are only millimetres in diameter and feed continuously. The polyp stage may last for years.
After an interval and stimulated by seasonal or hormonal changes, the polyp may begin reproducing asexually by budding and, in the Scyphozoa, is called a segmenting polyp, or a scyphistoma. Budding produces more scyphistomae and also ephyrae. Budding sites vary by species; from the tentacle bulbs, the manubrium (above the mouth), or the gonads of hydromedusae. In a process known as strobilation, the polyp's tentacles are reabsorbed and the body starts to narrow, forming transverse constrictions, in several places near the upper extremity of the polyp. These deepen as the constriction sites migrate down the body, and separate segments known as ephyra detach. These are free-swimming precursors of the adult medusa stage, which is the life stage that is typically identified as a jellyfish. The ephyrae, usually only a millimeter or two across initially, swim away from the polyp and grow. Limnomedusae polyps can asexually produce a creeping frustule larval form, which crawls away before developing into another polyp. A few species can produce new medusae by budding directly from the medusan stage. Some hydromedusae reproduce by fission.
Lifespan
Little is known of the life histories of many jellyfish as the places on the seabed where the benthic forms of those species live have not been found. However, an asexually reproducing strobila form can sometimes live for several years, producing new medusae (ephyra larvae) each year.
An unusual species, Turritopsis dohrnii, formerly classified as Turritopsis nutricula, might be effectively immortal because of its ability under certain circumstances to transform from medusa back to the polyp stage, thereby escaping the death that typically awaits medusae post-reproduction if they have not otherwise been eaten by some other organism. So far this reversal has been observed only in the laboratory.
Locomotion
Jellyfish locomotion is highly efficient. Muscles in the jellylike bell contract, setting up a start vortex and propelling the animal. When the contraction ends, the bell recoils elastically, creating a stop vortex with no extra energy input.
Using the moon jelly Aurelia aurita as an example, jellyfish have been shown to be the most energy-efficient swimmers of all animals. They move through the water by radially expanding and contracting their bell-shaped bodies to push water behind them. They pause between the contraction and expansion phases to create two vortex rings. Muscles are used for the contraction of the body, which creates the first vortex and pushes the animal forward, but the mesoglea is so elastic that the expansion is powered exclusively by relaxing the bell, which releases the energy stored from the contraction. Meanwhile, the second vortex ring starts to spin faster, sucking water into the bell and pushing against the centre of the body, giving a secondary and "free" boost forward. The mechanism, called passive energy recapture, only works in relatively small jellyfish moving at low speeds, allowing the animal to travel 30 percent farther on each swimming cycle. Jellyfish achieved a 48 percent lower cost of transport (food and oxygen intake versus energy spent in movement) than other animals in similar studies. One reason for this is that most of the gelatinous tissue of the bell is inactive, using no energy during swimming.
Ecology
Diet
Jellyfish are, like other cnidarians, generally carnivorous (or parasitic), feeding on planktonic organisms, crustaceans, small fish, fish eggs and larvae, and other jellyfish, ingesting food and voiding undigested waste through the mouth. They hunt passively using their tentacles as drift lines, or sink through the water with their tentacles spread widely; the tentacles, which contain nematocysts to stun or kill the prey, may then flex to help bring it to the mouth. Their swimming technique also helps them to capture prey; when their bell expands it sucks in water which brings more potential prey within reach of the tentacles.
A few species such as Aglaura hemistoma are omnivorous, feeding on microplankton which is a mixture of zooplankton and phytoplankton (microscopic plants) such as dinoflagellates. Others harbour mutualistic algae (Zooxanthellae) in their tissues; the spotted jellyfish (Mastigias papua) is typical of these, deriving part of its nutrition from the products of photosynthesis, and part from captured zooplankton. The upside-down jellyfish (Cassiopea andromeda) also has a symbiotic relationship with microalgae, but captures tiny animals to supplement their diet. This is done by releasing tiny balls of living cells composed of mesoglea. These use cilia to drive them through water and stinging cells which stun the prey. The blobs also seems to have digestive capabilities.
Predation
Other species of jellyfish are among the most common and important jellyfish predators. Sea anemones may eat jellyfish that drift into their range. Other predators include tunas, sharks, swordfish, sea turtles and penguins. Jellyfish washed up on the beach are consumed by foxes, other terrestrial mammals and birds. In general however, few animals prey on jellyfish; they can broadly be considered to be top predators in the food chain. Once jellyfish have become dominant in an ecosystem, for example through overfishing which removes predators of jellyfish larvae, there may be no obvious way for the previous balance to be restored: they eat fish eggs and juvenile fish, and compete with fish for food, preventing fish stocks from recovering.
Symbiosis
Some small fish are immune to the stings of the jellyfish and live among the tentacles, serving as bait in a fish trap; they are safe from potential predators and are able to share the fish caught by the jellyfish. The cannonball jellyfish has a symbiotic relationship with ten different species of fish, and with the longnose spider crab, which lives inside the bell, sharing the jellyfish's food and nibbling its tissues.
Main article: Jellyfish bloom
Jellyfish form large masses or blooms in certain environmental conditions of ocean currents, nutrients, sunshine, temperature, season, prey availability, reduced predation and oxygen concentration. Currents collect jellyfish together, especially in years with unusually high populations. Jellyfish can detect marine currents and swim against the current to congregate in blooms. Jellyfish are better able to survive in nutrient-rich, oxygen-poor water than competitors, and thus can feast on plankton without competition. Jellyfish may also benefit from saltier waters, as saltier waters contain more iodine, which is necessary for polyps to turn into jellyfish. Rising sea temperatures caused by climate change may also contribute to jellyfish blooms, because many species of jellyfish are able to survive in warmer waters. Increased nutrients from agricultural or urban runoff with nutrients including nitrogen and phosphorus compounds increase the growth of phytoplankton, causing eutrophication and algal blooms. When the phytoplankton die, they may create dead zones, so-called because they are hypoxic (low in oxygen). This in turn kills fish and other animals, but not jellyfish, allowing them to bloom. Jellyfish populations may be expanding globally as a result of land runoff and overfishing of their natural predators. Jellyfish are well placed to benefit from disturbance of marine ecosystems. They reproduce rapidly; they prey upon many species, while few species prey on them; and they feed via touch rather than visually, so they can feed effectively at night and in turbid waters. It may be difficult for fish stocks to re-establish themselves in marine ecosystems once they have become dominated by jellyfish, because jellyfish feed on plankton, which includes fish eggs and larvae.
As suspected at the turn of this century, jellyfish blooms are increasing in frequency. Between 2013 and 2020 the Mediterranean Science Commission monitored on a weekly basis the frequency of such outbreaks in coastal waters from Morocco to the Black Sea, revealing a relatively high frequency of these blooms nearly all year round, with peaks observed from March to July and often again in the autumn. The blooms are caused by different jellyfish species, depending on their localisation within the Basin: one observes a clear dominance of Pelagia noctiluca and Velella velella outbreaks in the western Mediterranean, of Rhizostoma pulmo and Rhopilema nomadica outbreaks in the eastern Mediterranean, and of Aurelia aurita and Mnemiopsis leidyi outbreaks in the Black Sea.
Some jellyfish populations that have shown clear increases in the past few decades are invasive species, newly arrived from other habitats: examples include the Black Sea, Caspian Sea, Baltic Sea, central and eastern Mediterranean, Hawaii, and tropical and subtropical parts of the West Atlantic (including the Caribbean, Gulf of Mexico and Brazil).
Jellyfish blooms can have significant impact on community structure. Some carnivorous jellyfish species prey on zooplankton while others graze on primary producers. Reductions in zooplankton and ichthyoplankton due to a jellyfish bloom can ripple through the trophic levels. High-density jellyfish populations can outcompete other predators and reduce fish recruitment. Increased grazing on primary producers by jellyfish can also interrupt energy transfer to higher trophic levels.
During blooms, jellyfish significantly alter the nutrient availability in their environment. Blooms require large amounts of available organic nutrients in the water column to grow, limiting availability for other organisms. Some jellyfish have a symbiotic relationship with single-celled dinoflagellates, allowing them to assimilate inorganic carbon, phosphorus, and nitrogen creating competition for phytoplankton. Their large biomass makes them an important source of dissolved and particulate organic matter for microbial communities through excretion, mucus production, and decomposition. The microbes break down the organic matter into inorganic ammonium and phosphate. However, the low carbon availability shifts the process from production to respiration creating low oxygen areas making the dissolved inorganic nitrogen and phosphorus largely unavailable for primary production.
These blooms have very real impacts on industries. Jellyfish can outcompete fish by utilizing open niches in over-fished fisheries. Catch of jellyfish can strain fishing gear and lead to expenses relating to damaged gear. Power plants have been shut down due to jellyfish blocking the flow of cooling water. Blooms have also been harmful for tourism, causing a rise in stings and sometimes the closure of beaches.
Jellyfish form a component of jelly-falls, events where gelatinous zooplankton fall to the seafloor, providing food for the benthic organisms there. In temperate and subpolar regions, jelly-falls usually follow immediately after a bloom.
Habitats
Most jellyfish are marine animals, although a few hydromedusae inhabit freshwater. The best known freshwater example is the cosmopolitan hydrozoan jellyfish, Craspedacusta sowerbii. It is less than an inch (2.5 cm) in diameter, colorless and does not sting. Some jellyfish populations have become restricted to coastal saltwater lakes, such as Jellyfish Lake in Palau. Jellyfish Lake is a marine lake where millions of golden jellyfish (Mastigias spp.) migrate horizontally across the lake daily.
Although most jellyfish live well off the ocean floor and form part of the plankton, a few species are closely associated with the bottom for much of their lives and can be considered benthic. The upside-down jellyfish in the genus Cassiopea typically lie on the bottom of shallow lagoons where they sometimes pulsate gently with their umbrella top facing down. Even some deep-sea species of hydromedusae and scyphomedusae are usually collected on or near the bottom. All of the stauromedusae are found attached to either seaweed or rocky or other firm material on the bottom.
Some species explicitly adapt to tidal flux. In Roscoe Bay, jellyfish ride the current at ebb tide until they hit a gravel bar, and then descend below the current. They remain in still waters until the tide rises, ascending and allowing it to sweep them back into the bay. They also actively avoid fresh water from mountain snowmelt, diving until they find enough salt.
Parasites
Jellyfish are hosts to a wide variety of parasitic organisms. They act as intermediate hosts of endoparasitic helminths, with the infection being transferred to the definitive host fish after predation. Some digenean trematodes, especially species in the family Lepocreadiidae, use jellyfish as their second intermediate hosts. Fish become infected by the trematodes when they feed on infected jellyfish.
Relation to humans
Jellyfish have long been eaten in some parts of the world. Fisheries have begun harvesting the American cannonball jellyfish, Stomolophus meleagris, along the southern Atlantic coast of the United States and in the Gulf of Mexico for export to Asia.
Jellyfish are also harvested for their collagen, which is being investigated for use in a variety of applications including the treatment of rheumatoid arthritis.
Aquaculture and fisheries of other species often suffer severe losses – and so losses of productivity – due to jellyfish.
Products
Main article: Jellyfish as food
In some countries, including China, Japan, and Korea, jellyfish are a delicacy. The jellyfish is dried to prevent spoiling. Only some 12 species of scyphozoan jellyfish belonging to the order Rhizostomeae are harvested for food, mostly in southeast Asia. Rhizostomes, especially Rhopilema esculentum in China (海蜇 hǎizhé, 'sea stingers') and Stomolophus meleagris (cannonball jellyfish) in the United States, are favored because of their larger and more rigid bodies and because their toxins are harmless to humans.
Traditional processing methods, carried out by a jellyfish master, involve a 20- to 40-day multi-phase procedure in which, after removing the gonads and mucous membranes, the umbrella and oral arms are treated with a mixture of table salt and alum, and compressed. Processing makes the jellyfish drier and more acidic, producing a crisp texture. Jellyfish prepared this way retain 7–10% of their original weight, and the processed product consists of approximately 94% water and 6% protein. Freshly processed jellyfish has a white, creamy color and turns yellow or brown during prolonged storage.
In China, processed jellyfish are desalted by soaking in water overnight and eaten cooked or raw. The dish is often served shredded with a dressing of oil, soy sauce, vinegar and sugar, or as a salad with vegetables. In Japan, cured jellyfish are rinsed, cut into strips and served with vinegar as an appetizer. Desalted, ready-to-eat products are also available.
Biotechnology
The hydromedusa Aequorea victoria was the source of green fluorescent protein, studied for its role in bioluminescence and later for use as a marker in genetic engineering.
Pliny the Elder reported in his Natural History that the slime of the jellyfish "Pulmo marinus" produced light when rubbed on a walking stick.
In 1961, Osamu Shimomura extracted green fluorescent protein (GFP) and another bioluminescent protein, called aequorin, from the large and abundant hydromedusa Aequorea victoria, while studying photoproteins that cause bioluminescence in this species. Three decades later, Douglas Prasher sequenced and cloned the gene for GFP. Martin Chalfie figured out how to use GFP as a fluorescent marker of genes inserted into other cells or organisms. Roger Tsien later chemically manipulated GFP to produce other fluorescent colors to use as markers. In 2008, Shimomura, Chalfie and Tsien won the Nobel Prize in Chemistry for their work with GFP. Man-made GFP became widely used as a fluorescent tag to show which cells or tissues express specific genes. The genetic engineering technique fuses the gene of interest to the GFP gene. The fused DNA is then put into a cell, to generate either a cell line or (via IVF techniques) an entire animal bearing the gene. In the cell or animal, the artificial gene turns on in the same tissues and the same time as the normal gene, making a fusion of the normal protein with GFP attached to the end, illuminating the animal or cell reveals what tissues express that protein—or at what stage of development. The fluorescence shows where the gene is expressed.
Aquarium display
Jellyfish are displayed in many public aquariums. Often the tank's background is blue and the animals are illuminated by side light, increasing the contrast between the animal and the background. In natural conditions, many jellies are so transparent that they are nearly invisible. Jellyfish are not adapted to closed spaces. They depend on currents to transport them from place to place. Professional exhibits as in the Monterey Bay Aquarium feature precise water flows, typically in circular tanks to avoid trapping specimens in corners. The outflow is spread out over a large surface area and the inflow enters as a sheet of water in front of the outflow, so the jellyfish do not get sucked into it. As of 2009, jellyfish were becoming popular in home aquariums, where they require similar equipment.
Stings
Jellyfish are armed with nematocysts, a type of specialized stinging cell. Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom, but only some species' venom causes an adverse reaction in humans. In a study published in Communications Biology, researchers found a jellyfish species called Cassiopea xamachana which when triggered will release tiny balls of cells that swim around the jellyfish stinging everything in their path. Researchers described these as "self-propelling microscopic grenades" and named them cassiosomes.
The effects of stings range from mild discomfort to extreme pain and death. Most jellyfish stings are not deadly, but stings of some box jellyfish (Irukandji jellyfish), such as the sea wasp, can be deadly. Stings may cause anaphylaxis (a form of shock), which can be fatal. Jellyfish kill 20 to 40 people a year in the Philippines alone. In 2006 the Spanish Red Cross treated 19,000 stung swimmers along the Costa Brava.
Vinegar (3–10% aqueous acetic acid) may help with box jellyfish stings but not the stings of the Portuguese man o' war. Clearing the area of jelly and tentacles reduces nematocyst firing. Scraping the affected skin, such as with the edge of a credit card, may remove remaining nematocysts. Once the skin has been cleaned of nematocysts, hydrocortisone cream applied locally reduces pain and inflammation. Antihistamines may help to control itching. Immunobased antivenins are used for serious box jellyfish stings.
In Elba Island and Corsica dittrichia viscosa is now used by residents and tourists to heal stings from jellyfish, bees and wasps pressing fresh leaves on the skin with quick results.
Mechanical issues
Jellyfish in large quantities can fill and split fishing nets and crush captured fish. They can clog cooling equipment, having disabled power stations in several countries; jellyfish caused a cascading blackout in the Philippines in 1999, as well as damaging the Diablo Canyon Power Plant in California in 2008. They can also stop desalination plants and ships' engines.