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They are almost the same colour as sand and as round as the sand balls they create. They bolt into their burrows at the slightest sign of danger. To observe them, stay still and avoid casting a shadow over them. Then look out for a moving ball of sand. Sand bubbler crabs eat the thin coating of detritus on sand grains.
Sand bubbler crabs scour the sand to feed, and leaving sand pellets after scouring
This sand bubbler crab, Scopimera intermedia, was feeding in front of its burrow. You can see a sand pellet in front of its mouth.
actual size 5 to 10 cm. So not so big as it looks. And he is blowing bubbles!
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (Greek: brachy = short, ura = tail), or where the reduced abdomen is entirely hidden under the thorax. They are generally covered with a thick exoskeleton, and are armed with a single pair of chelae (claws). Crabs are found in all of the world's oceans; there are also many freshwater and terrestrial crabs, particularly in tropical regions. Crabs vary in size from the pea crab, only a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 m. True crabs have five pairs of legs, the first of which are modified into a pair of claws and are not used for locomotion. In all but a few crabs (for example, Raninoida), the abdomen is folded under the cephalothorax in the adult stage. The mouthparts of crabs are covered by flattened maxillipeds, and the front of the carapace does not form a long rostrum [2]. The gills of crabs are formed of flattened plates ("phyllobranchiate"), resembling those of shrimp, but of a different structure [3].They can also be the size of a pea, or even smaller.
Most crabs show clear sexual dimorphism and so can be easily sexed. The abdomen, which is held recurved under the thorax, is narrow in males. In females, however, the abdomen retains a greater number of pleopods and is considerably wider [4]. This relates to the carrying of the fertilised eggs by the female crabs (as seen in all pleocyemates). In those species in which no such dimorphism is found, the position of the gonopores must be used instead. In females, these are on the third pereiopod, or nearby on the sternum in higher crabs; in males, the gonopores are at the base of the fifth pereiopods or, in higher crabs, on the sternum nearby.
source en.wikipedia.org/wiki/Brachyura
Krabben behoren tot de decapoda, de tienpotigen. Krabben hebben vier paar looppoten en één paar scharen. De samengestelde ogen van krabben staan op steeltjes en kunnen worden ingeklapt in gleuven op de kop. Krabben hebben een stevig, enkelvoudig rugpantser (carapax) en een gesegmenteerd buikpantser. De vrouwtjes zijn te onderscheiden van de mannetjes door de driehoekige gesegmenteerde plaat aan de achteronderzijde bij de anus; vrouwtjes hebben meer segmenten. Ooit was dit buikpantser naar achteren geklapt, en vormde het achterlijf, zoals bij kreeften nog steeds het geval is. Krabben eten zeer elegant: met de grootste schaar, de kraakschaar, wordt de prooi vastgehouden en met de kleine, de grijpschaar, worden hier stukjes van afgenomen en naar de monddelen gebracht, waar maar liefst zes paar gelede individueel gestuurde 'pootjes' (de mandibels, maxillen en maxillipedes) het voedsel verkleinen en de mond in werken. Niet alle krabben hebben verschillende scharen, zoals bijvoorbeeld de zwemkrab. Op de schildrand naast de ogen hebben krabben twee voelsprieten, die meestal niet groot worden; ze spelen een rol bij het aftasten van de directe omgeving, zoals rotsspleten. Veel krabben blijven klein maar er zijn uitzonderingen, zoals de reuzenkrab. Ook de noordzeekrab kan flink worden: tot 70 cm spanwijdte van de scharen. Krabben halen adem met hun kieuwen. Deze zitten in het rugschild aan de achterzijde, en functioneren zolang ze nat blijven. Een krab moet dus regelmatig met water in aanraking komen om niet te stikken.
This pattern was one of many we passed by as we walked along Noppharat Thara Beach. I believe this crab is known as a sand bubbler. At times it felt like we were walking through a sand art gallery. Ao Nang, Krabi, Thailand
Just too stikin' cute!
I saw another pic online of these guys, however I don't know who to credit for the inspiration.
Thanks whoever you are =D
Sand bubbler crabs leave behind a sea of sand balls along the beach as the sun sets in the background. Photo by ABC Open contributor adventurepilot
Ko Lanta Yai - patterns created by crabs of the Dotillidae family "bubbler crabs" they filter sand through their mouths to extract nutrients, the filtered sand is left as small pellets or bubbles, often in fern like displays.
My backyard is full with sand-bubbler crab. Those formations are so artistic sometimes (yes I am living close to the seashore).
These magnificent little fellows emerge from their burrow, grab a chunk of sand and push it through their jaws, consuming the detritus within and forming the sand into a ball nearly the size of their body. The used pellet is then tossed over their shoulder and it's onto the next bit.
The beach was covered with these filter feeding crabs. Thousands of holes, each surrounded by hundreds of balls, parting only for a little driveway out to the sea.
Sand Bubbler Crab: Scopimera inflata (Family Ocypodidae)
Sand Bubbler Crab on Wikipedia
Sand bubbler crabs live in burrows in the sand, where they remain during high tide. When the tide is out, they emerge on to the surface of the sand. They begin feeding by collecting sand and quickly sifting it in search of food. When done the crab gathers it into a sand bubble and tosses it behind its legs. You can almost tell how long the tide has been out by the patterns of their sand balls. The more intricate the pattern of sand balls, the longer the tide has been out.
scanned slide
see en.wikipedia.org/wiki/Sand_bubbler_crab and www.flickr.com/photos/alan_cressler/4184644788/
Here's the crab - www.flickr.com/photos/miangusapa/5123412155/
www.flickr.com/photos/49563472@N07/galleries/721576248178...
a whole gallery of "Crab Ball Crop Circles" -
good shot - www.flickr.com/photos/alan_cressler/4184642474/
my lichen photos by genus - www.flickr.com/photos/29750062@N06/collections/7215762439...
my photos arranged by subject, e.g. mountains - www.flickr.com/photos/29750062@N06/collections
I really don't know what these are. They were on the beach (Costa Rica again) in the area of some crab holes. There was a whole line of these with the tracks beside them as you see here. Anyone? Thank you, AMUK:
Sand bubbler crabs are not found on the sand bar. They are almost the same colour as sand, and as round as the sand balls they create. They bolt into their burrows at the slightest sign of danger. To observe them, stay still and avoid casting a shadow over them. Then look out for a moving ball of sand!
These are patterns left on the sand by crabs. From the moment I saw them for first time I kept on wondering what it is. Well, I did a little google research and will share the little information I found....
They are Sand bubbler crabs that live on sandy beaches in the tropical Indo-Pacific.
These small crabs live in burrows in the sand, where they remain during high tide. When the tide is out, they emerge on to the surface of the sand, and scour the sand for food, forming it into inflated pellets, which cover the sand. The balls are actually the left overs after feeding.
The crabs emerge as soon as the tide recedes. You can almost tell how long the tide has been out by the patterns of their sand balls. The more intricate the pattern of sand balls, the longer the tide has been out.
Con marea baja los minúsculos cangrejos "Sand Bubbler Crab" (Scopimera sp.) excavan su madriguera, filtrando detritus de la arena para comerselo. Con la arena restante forman pequeñas bolas y las depositan en los alrededores, creando dibujos bastante artisticos.
Railay Beach, Phranang Peninsula, Krabi province, southern Thailand.
Cámara digital Canon PowerShot G10
Diafragma f/8
Velocidad 1/160 seg
Khao Sam Roi Yot National Park, Thailand
"In a visible daily cycle, bubble crabs emerge by the thousands from their burrows in the beach. They are barely the size of a human fingernail. With a practiced sense of purpose, they gather grains of sand and work them through their mouths, gleaning off the film of algae and microbes that coat each sand grain’s surface. The nutrition gained from each mouthful is minute, but through the course of the day, a crab will move thousands of sand grains, which it forms into perfect spheres."
Sand bubbler crabs (or sand-bubblers) are crabs of the genera Scopimera and Dotilla in the family Dotillidae. They are small crabs that live on sandy beaches in the tropical Indo-Pacific. During the low tide, they form inflated sand pellets that are disintegrated by the incoming high tide.
DESCRIPTION
Sand bubbler crabs are small crabs, around 1 cm across the carapace, and they are characterised by the presence of "gas windows" on the merus of the legs; in Dotilla, these windows are also present on the thoracic sternites. A similar system has evolved in parallel in the porcelain crab genus Petrolisthes
DISTRIBUTION
Sand bubbler crabs are widespread across the Indo-Pacific region, where they occur abundantly on sandy beaches in the tropics and sub-tropics.
ECOLOGY AND SUB-BEHAVIOUR
Sand bubbler crabs live in burrows in the sand, where they remain during high tide. When the tide is out, they emerge on to the surface of the sand, and scour the sand for food, forming it into inflated pellets, which cover the sand. The crabs work radially from the entrance to their burrow, which they re-enter as the tide rises and disintegrates the pellets. The material consumed by sand bubbler crabs has a very low concentration of organic matter, which is concentrated by egestion of indigestible material.
TAXONOMY
TAXONOMIC HISTORY
The first sand bubbler crab to be described was Cancer sulcatus (now Dotilla sulcata) by Peter Forsskål in 1775. The genus Scopimera was originally described as a subgenus of Ocypode by Wilhem de Haan in 1833, although the first species, Scopimera globosa was not validly described until 1835. At the same time, De Haan tried to erect the genus Doto for Forskål's Cancer sulcatus, not realising that the name was preoccupied by the mollusc genus Doto. The first available name for that genus was published by William Stimpson in 1858, who called it Dotilla. Ongoing revisions are likely to split the current genus Scopimera into at least two genera.
SPECIES
Eight species of Dotilla and fifteen of Scopimera are currently recognised.
WIKIPEDIA
Sand Bubbler Crabs emerge at low tide to feed. They process damp sand to extract organic matter
and then roll the processed sand into balls and park them in lines radiating from their holes to avoid repeating the routine on sand they have already scoured. The crabs are quite tiny and many of the ball patterns are quite artistic!