02 Nucella lapillus

Squat, extremely exposed-shore form with short spire height (1) c. 24% of shell height. Large aperture 76% of height. Fourteen well developed, flattened, spiral ridges on body-whorl. Shell height 25 mm, breadth 17.4 mm. West coast of Hoy, Orkney (Atlantic fetch over 3000km). July 1973.

 

SPECIES DESCRIPTION PART A BELOW

Key id. features: flic.kr/p/oErLAb

SPECIES DESCRIPTION PART B at flic.kr/p/oGiBxM

Sets of OTHER SPECIES:

www.flickr.com/photos/56388191@N08/collections/

Illustrated pdf of account available at

www.researchgate.net/profile/Ian_Smith19/contributions

 

Nucella lapillus (Linnaeus, 1758)

 

Synonyms: Purpura lapillus (Linnaeus, 1758); Thais lapillus (Linnaeus, 1758); Polytropa lapillus (Linnaeus, 1758);

Vernacular: Dog whelk; Dog winkle; Purple; Rock whelk; Horse winkle (English); Gwichiad/Chwalcen y cŵn; Cragen foch felen (Welsh); Purpursnegl (Danish & Norwegian); purperslak (Dutch); Pourpre petit pierre; pourpre (French); Nordische Steinchenschneke/Purpurschneke (German); Purpur snäcke (Swedish);

 

GLOSSARY BELOW

 

Shell Description

Adults usually 17 to 30mm high, up to 45mm littorally 1Nl flic.kr/p/oErLAb and over 60mm sublittorally. Shape varies from long and slender (spire c. 55%, of shell height) 5Nl flic.kr/p/oCvYLG to short and squat (spire c. 24%, of shell-height) 2Nl flic.kr/p/oEkeZW . Apex slightly twisted, sharp if uneroded. Whorls moderately convex. Sutures usually slight, may be deeper near apex 3Nl flic.kr/p/oGiBxM , can be almost obliterated by erosion 4Nl flic.kr/p/oGiAZH . Aperture height varies greatly, about 45% 5Nl flic.kr/p/oCvYLG to 80% 2Nl flic.kr/p/oEkeZW of shell height. Juveniles and sub-adults (less than c17mm high) have thin shell- walls with sharp outer lip 6Nl flic.kr/p/oo3ZVh . Adults (when 17mm or more high) usually cease longitudinal growth and develop thick shell-walls and line of blunt bosses within outer lip of aperture 7Nl flic.kr/p/oCvWwm . Sometimes more than one row of bosses if growth arrested prematurely. Outer lip smooth, interior slightly shiny, not sharp, but tapers from bosses to edge. Aperture rapidly constricts into throat 8Nl flic.kr/p/oExH2t . Adapical angle acute when young 6Nl flic.kr/p/oo3ZVh , rounded as shell thickens 9Nl flic.kr/p/oEh5nn . Short, straight, open siphonal canal at base of aperture. Columellar and parietal lips are wide, smooth and slightly shiny 10Nl flic.kr/p/oCvTfw ; columellar lip overhangs siphonal canal slightly; parietal lip continuous with outer lip through the adapical angle. Siphonal fasciole pronounced on some 11Nl flic.kr/p/ooe2CW . Sculpture of flattened, spiral ridges (about 12 on body-whorl) 12Nl flic.kr/p/ooeM9v & 2Nl flic.kr/p/oEkeZW , often indistinct or absent 9Nl flic.kr/p/oEh5nn . Growth lines usually indistinct. Newly hatched young have globular, smooth, glossy shell (protoconch) of 2½ whorls about 1mm high. Early growth to c.3mm very often has prominent imbricate sculpture 13Nl flic.kr/p/ooeKHK which, with the protoconch, may persist on early whorls of uneroded adults 3Nl flic.kr/p/oGiBxM and occasionally continue on later whorls 14Nl flic.kr/p/oEHJRv & 15Nl flic.kr/p/oEvg6d . Ground colour white 7Nl flic.kr/p/oCvWwm , whitish-grey 4Nl flic.kr/p/oGiAZH , yellow 12Nl flic.kr/p/ooeM9v , orange 16Nl flic.kr/p/oCFXZ1 , brown to black 17Nl flic.kr/p/oGtyn8 , or mauve to pink 3Nl flic.kr/p/oGiBxM . Interior of aperture shows exterior colours on thin translucent young shells 6Nl flic.kr/p/oo3ZVh , and thickened adult shells are often coloured internally 9Nl flic.kr/p/oEh5nn , 10Nl flic.kr/p/oCvTfw & 12Nl flic.kr/p/ooeM9v . Sometimes exterior colours combined in spiral bands; narrow and confined to grooves between spiral ridges 18Nl flic.kr/p/ooe7M2 , or broad 6Nl flic.kr/p/oo3ZVh . Growths 7Nl flic.kr/p/oCvWwm , encrustations 19Nl flic.kr/p/oEFXeY and erosion 4Nl flic.kr/p/oGiAZH can affect colour. Light-horn coloured periostracum often on small juveniles 13Nl flic.kr/p/ooeKHK , absent or insignificant on adults. Broad, angular, mahogany, non-spiral operculum 20Nl flic.kr/p/ooeFck ; thin outer face extruded from transverse groove at anterior of opercular disc has many fine, gently-curving growth lines increasing in length away from nucleus on posterior (labial) edge; thick inner face made of stack of annual growth plates (adventitious layers extruded from circles of glands on opercular disc) with excentric nucleus and matt surface where opercular disc attached (termination of columellar muscle). Posterior (labial) margin beyond disc attachment (c.25% of total operculum surface) covered by shiny varnish from transverse groove across posterior of opercular disc. Operculum nearly opaque on old adults, but younger ones have translucent operculum through which adventitious plates show as strong concentric rings that obscure fine exterior growth lines 21Nl flic.kr/p/oojcrR .

 

Body Description

Flesh, apart from mantle, entirely pure-white or yellowish-white, variably translucent 22Nl flic.kr/p/oGy5Jx , sometimes opaque white freckles visible on surface of more translucent parts 23Nl flic.kr/p/oENedn . Head consists of transverse ridge at juncture of cephalic tentacles. No snout visible, except, when feeding, a short, thin proboscis 39bNl flic.kr/p/DAshoD is everted like a sock turned inside-out from opening at base of head’s anterior 24Nl flic.kr/p/oENe6Z . Pink buccal mass 22Nl flic.kr/p/oGy5Jx with narrow, short radula, about 30% of shell length; only three teeth per row 25Nl flic.kr/p/ooiMib . Long, tapering, rounded cephalic tentacles; translucent white, sometimes with opaque white flecks 23Nl flic.kr/p/oENedn . Basal two thirds of cephalic tentacle thickened by fusion with eye peduncle; black eye on summit of outer face of thickened section 26Nl flic.kr/p/ooiQC7 ; divided ventrally on one examined specimen 27Nl flic.kr/p/oojdTP . Mantle edge thickened, usually yellowish even on pure white animals 28Nl flic.kr/p/oGy3si , occasionally with a little brown. Mantle folded into white inhalent siphon on left of body, continues as channel to osphradium and substantial buff ctenidium within mantle cavity; siphon extends only slightly beyond end of siphonal canal of shell 29Nl flic.kr/p/oEwBUT . Faint pink of myoglobin-rich buccal mass, white salivary glands and other internal organs sometimes visible behind head of well-extended animal 22Nl flic.kr/p/oGy5Jx . Flat, strap-like (when live) penis attached sub-dorsally behind right tentacle; recurved up to 360° 24Nl flic.kr/p/oENe6Z , may be pulled straighter during emergence of body from shell 30Nl flic.kr/p/oEwA7p . Foot can change between oblong 31Nl flic.kr/p/ooMS7c and bluntly oval 32Nl flic.kr/p/ooMja8 , often constricted behind propodium. Anterior edge bilaminate 33Nl flic.kr/p/ooMRLT , sole and dorsum coloured as body. Small opercular disc does not extend beyond or overlap edge of operculum 24Nl flic.kr/p/oENe6Z , apart from anterior edge of operculum being exuded from opercular groove 27Nl flic.kr/p/oojdTP . Strong white columellar muscle attaches opercular disc to columella of shell 34Nl flic.kr/p/oFgVyD . Sole of foot divided along midline; most obvious when foot folds along it 23Nl flic.kr/p/oENedn . Sucker-like accessory boring organ (ABO) in sac within foot on midline near anterior; when everted swells into a large proboscis-like projection. Female has ventral pedal gland for moulding egg capsules, anterior to centre of sole.

 

Internal anatomy

When extracted from shell, organs in place but indistinctly seen through translucent mantle on anterior half of body. When mantle cut along pallial inhalent channel and opened out to the right of the animal like a page of a book, organs attached to its inner face are displaced but more clearly visible.

KEY to items on images 35aNl flic.kr/p/oF4opC & 35bNl flic.kr/p/oF4o3W (extracted male), 36Nl flic.kr/p/ooMch1 (opened male) 37Nl flic.kr/p/oF1kCZ (extracted female) 38Nl flic.kr/p/oFfdey (opened female). If key is read in order, the functions and inter-relationship of the organs may be understood.

 

Mantle

1: mantle edge - substantial, opaque, yellowish, slightly flounced, anterior border of mantle skirt. Only part that produces exterior layers of shell. Sometimes flounces exaggerated and make protruding shell-growth that forms imbricate sculpture. (Images 35a&b, 36, 37)

2: mantle skirt - forms roof of mantle cavity and, when uncut, partially obscures organs within. (Images 35a&b, 37)

Respiratory features

3: siphon – white, folded extension of mantle that rests in shell’s siphonal canal and draws in inhalent current of water when animal extended. (Images 35a, 36, 37)

4: pallial inhalent channel – distinct, white fold in mantle forming a channel from siphon to osphradium. (Images 35a, 36, 37)

5: osphradium - dark, bipectinate chemo-receptor at inner end of inhalent channel that tests water approaching ctenidium for quality and scents of food, prey, predators and/or mates. So highly developed on Nucella that Jeffreys (1867) thought it was second ctenidium. (Images 35a, 36, 37, 38)

6: ctenidium - substantial, buff-white gill with many fine leaflets that receive oxygen from inhalent water, and oxygenate blood passing through them. (Images 35a&b, 36, 37, 38)

7: hypobranchial gland – puckered gland that produces mucous to trap particles from inhalent water before reaches ctenidium, and to transport particles out of mantle cavity. Other functions might be attraction of mates by scent, and acrid smell/taste to discourage predators. Initially cream-white, changing to yellow, green, purple etc when exposed to light and air. (Images 35a&b, 36,37)

Vascular features

8: kidney – de-oxygenated blood has urea etc. removed and excreted by kidney before passing to efferent renal vein [9]. (Images 35a&b)

9: efferent renal vein – carries blood away from kidney. (Image 35b)

10: Hypobrachial vessels – carry blood from efferent renal vein through hypobranchial gland to afferent vessel of ctenidium [11]. (Image 35b)

11: afferent vessel of ctenidium – receives blood from hypobranchial vessels and passes it into leaflets of adjacent ctenidium for oxygenation. (Image 35b)

12: rectal gland - long, linear gland; dark brown to purple-black in adults. Function uncertain, perhaps produces substances that supplement the excretory activity of the kidney. (Images 35a&b, 37, 38)

Alimentary features

13: buccal mass – pink as rich in myoglobin; contains odontophore and anterior of radula used in rasping prey. (Image 36)

14: acinous salivary gland - compound gland of many small rounded sacs that secrete enzymes for external pre-digestion/ liquefaction of prey. (Image 36)

15: gland of Leiblein - secretes enzymes for internal digestion of ingested liquefied prey. (Image 36)

16: digestive gland – mass of branching tubules and ducts occupying majority of visceral mass (spiral ‘tail’ of body); most visible feature, except in breeding season when much may be covered by ovary or testis. Receives solution of digested food from stomach into tubules where taken up by absorbing digestive cells and passed into blood bathing the tubules. (Images 35a&b, 36, 37, 38)

Reproductive features

17: ovary- gland that produces eggs. (Image 37)

18: albumen gland - translucent whitish gland that secretes albumen for nutrition of developing eggs. (Images 37, 38)

19: sperm ingesting gland - dark brown blind tubules in female where sperm excess to requirements is engulfed and digested by cells; gland is used to establish sex of specimens as penis can occur on females affected by imposex. (Image 37, 38)

20: capsule gland - secretes fibrous wall of capsule containing ova, but does not give it its final shape. (Images 37, 38)

21: testis - gland that produces spermatozoa. (Images 35a&b, 36)

22: prostate – pink gland that secretes fluid which, with spermatozoa and seminal vesicle fluid, forms the semen. (Images 35b, 36)

23: penis - on males, and on females affected by imposex caused by tributyltin pollution. (Image 36)

SPECIES DESCRIPTION PART B at flic.kr/p/oGiBxM

 

Glossary

abapertural = away from aperture.

acinous salivary gland = compound gland of many small rounded sacs that secrete enzymes for external predigestion/ liquefaction of prey.

 

adapertural = towards aperture.

adapical = towards the apex of the shell.

afferent = carrying towards. (e.g. of vessel carrying blood, see efferent.)

 

aperture = mouth of gastropod shell; outlet for head and foot.

Ballantine scale = biologically-defined wave exposure scale (see references).

bipectinate = feather-like, with narrow filaments either side of central stalk.

capsule gland = secretes fibrous wall of capsule containing ova.

cephalic = (adj.) of or on the head.

chelae = (singular chela) pincers of crabs and other crustacea.

cilia = (pl.) vibrating linear extensions of membrane used in feeding or locomotion. (“cilium” singular).

 

ciliated = (adj.) coated with cilia.

 

columella = solid or hollow axial “little column” around which gastropod shell spirals; hidden inside shell, except on final whorl next to lower part of inner lip of aperture where hollow ones may end in an umbilicus or siphonal canal.

 

columellar = (adj.) of or near central axis of spiral gastropod.

columellar lip = lower (abapical) part of inner lip of aperture.

 

columellar muscle = attaches body, including opercular disc, to columella of shell; contraction of muscle withdraws body within shell, and pulls operculum to seal aperture.

 

commensal = (adj.) obtaining nutrients, shelter, support, or locomotion from a host species, without causing it significant detriment.

 

conchiolin = horny flexible protein that forms the matrix for the deposition of calcium carbonate to create a mollusc’s shell.

 

ctenidium = comb-like molluscan gill; usually an axis with a row of filaments either side.

 

ditaxic = (of locomotion waves on foot) double series of waves, out of phase with each other, one series on each side of central furrow on sole.

 

direct = (of locomotion waves on foot) waves travel from posterior to anterior.

 

efferent = carrying away from. (e.g. of vessel carrying blood from ctenidium).

fasciole = (see siphonal fasciole)

gland of Leiblein = secretes enzymes for internal digestion.

 

height = (of gastropod shells) distance from apex of spire to base of aperture.

 

hypobranchial gland = thickened, sometimes puckered, tissue on roof of mantle cavity of many gastropods. Emits mucous to trap particles from

inhalent water before it reaches ctenidium. Often other biologically active compounds produced. Gland occurs also in some bivalves and cephalopods (ink sac).

 

imbricate = shell sculpture of growth-line ornament overlapping like roof tiles.

MHWN = mean high water neap tide level (mean level reached by weakest high tides for a few days every fortnight).

 

MHWS = mean high water spring tide level (mean level reached by highest tides for a few days every fortnight; Pelvetia zone on rocky coasts).

 

MLWN = mean low water neap tide level (mean level reached by weakest low tides for a few days every fortnight. i.e. those that fall the least).

 

mantle = sheet of tissue that secretes the shell and forms a cavity for the gill in most marine molluscs.

 

mesopodium = middle section of gastropod foot. (see propodium & metapodium).

 

metapodium = rear section of gastropod foot. (see mesopodium & propodium).

 

myoglobin – red oxygen-binding protein in muscle tissue; often in buccal-mass muscles of gastropods. Similar to red haemoglobin in vertebrate blood, but green haemocyanin is usual oxygen-carrier in mollusc blood. See www.researchgate.net/publication/251227038_Radular_myoglo...

 

N = (See Newton).

Newton = (abbreviation N) force exerted by Earth’s gravity on approx. 100g.

 

odontophore = cartilaginous “tongue” that supports and protracts /retracts the radula.

 

opercular = (adj.) of the operculum.

opercular disc = part of foot attached to inner face of operculum.

opercular lobe = extension of opercular disc round edge of part of operculum.

operculum = plate of horny conchiolin, rarely calcareous, used to close shell aperture.

 

osphradium = chemo-receptor organ in molluscs that tests inhalent water flow approaching ctenidium (gill) for “smell” of food, prey, predators, mates and/or water quality.

 

penes = (plural of penis) male copulatory organs.

periostracum = thin horny layer of chitinous material often coating shells.

plankton = animals and plants that drift in pelagic zone (main body of water).

propodium = front section of gastropod foot. (Cf. mesopodium & metapodium).

prosobranchia = 20th Century term for subclass of Gastropoda that included most marine snails with ctenidia. Now distributed between several subclasses. See note at www.marinespecies.org/aphia.php?p=taxdetails&id=102

 

rectal gland = (a.k.a. anal gland) Function uncertain, perhaps produces substances that supplement the excretory activity of the kidney.

 

retrograde = (of locomotion waves on foot) waves travel from anterior to posterior.

sessile = (of organism) fixed in one place, e.g. barnacles.

siphon = extension of mantle to form a channel for inhalent respiratory water current.

 

siphonal canal = grooved or tubular extension of outer lip of the shell aperture on some snails to support the siphon.

 

siphonal fasciole = raised rib, ridge or band along abapertural side of siphonal canal, formed by successive edges of canal.

 

sperm ingesting gland = (in female Nucella lapillus) group of dark brown blind-ended tubules at posterior of capsule gland where excess sperm unrequired by female are trapped, engulfed by cells and digested.

 

suture = groove or line where whorls of gastropod shell adjoin.

 

vas deferens = tube carrying sperm to male’s penis.

veliger = shelled larva of marine gastropod or bivalve mollusc which swims by beating cilia of a velum (bilobed flap).

Done