01 Calyptraea chinensis

Spiral protoconch (1) on apex. Concentric growth lines (2). Thin yellowish periostracum much eroded. Aperture diameter 6 mm. Portland Harbour, England, April 2012.

 

FULL ACCOUNT BELOW

PDF available at www.researchgate.net/publication/376415643_Calyptraea_chi...

Sets of OTHER SPECIES at: www.flickr.com/photos/56388191@N08/collections/.

 

Calyptraea chinensis (Linnaeus, 1758)

Synonyms: Patella chinensis Linnaeus, 1758; Calyptraea sinensis (Linnaeus, 1758);

Vernacular: Chinaman’s hat; Chinese hat shell; Cup and saucer limpet; Het Tsieinî (Welsh); Chinees hoedje (Dutch); Chapaeu chinois (French); Chinesenhut (German); Kineziko kapelo (Greek).

 

Glossary below.

 

Shell Description

Patelliform cone (= body whorl) lacking any spire except one and half tiny whorls of larval protoconch at apex 1Cc flic.kr/p/irNS4J which is often eroded away in later adult life. Cone of female up to 5mm high; diameter of near-circular aperture usually up to 15mm, exceptionally 21mm; males maximum diameter about 8mm. Profile of cone has concave anterior and convex posterior 2Cc flic.kr/p/irNS6C . Individuals living on pebble often steeper than those on flatter surfaces. Apex almost central 3Cc flic.kr/p/irNA6H , quite sharp with nipple-like tip if protoconch not eroded 4Cc flic.kr/p/irPrzF . No external sculpture apart from protoconch and concentric growth lines 1Cc flic.kr/p/irNS4J, but sometimes the cone is stepped, and/or has small tubercles (Wigham & Graham, 2017). Posterior half of interior partitioned by tongue-shaped, shelf-like septum, originating narrowly at apex and widening through half a helical spiral turn to near the thin bevelled rim of the aperture 5Cc flic.kr/p/irNzUa . As with other patelliform species, the larval operculum is lost on metamorphosis to adult form. Unpatterned, matt, whitish or yellowish exterior, thin perimeter often translucent 3Cc flic.kr/p/irNA6H ; shiny pearl-white interior, occasionally with brown blemishes. Thin yellowish periostracum often eroded 1Cc flic.kr/p/irNS4J .

Body Description

Translucent white, fawn-white or grey-white 9Cc flic.kr/p/irP7My with many flakes of opaque white. Short snout consists of two distinct lobes separated by a narrow groove 6Cc flic.kr/p/irNREY which opens widely when the radula protrudes 7Cc flic.kr/p/irNRnJ . Cephalic tentacle either side of snout has smooth, stout, cylindrical base with eye, and a rough, tapering, more yellowish, distal half 6Cc flic.kr/p/irNREY . Small semicircular neck-lobe behind each tentacle 8Cc flic.kr/p/irPraT . Shell muscle attached to septum of shell. Anterior of oval foot bilaminate with small propodial extensions 9Cc flic.kr/p/irP7My . Sole translucent whitish with opaque white marks 9Cc flic.kr/p/irP7My . Mantle similar colours to body, but may be more yellowish and have orange marks 8Cc flic.kr/p/irPraT . Pallial filter of porous sheet of mucus flecked with opaque white stretches from mantle skirt to left (inhalent) side of body 10Cc flic.kr/p/irPqTk . Large, deep mantle cavity occupies anterior half of shell. Monopectinate ctenidium many times larger than usual on gastropods 11Cc flic.kr/p/irNz5K ; greatly elongated filaments hang from roof of mantle cavity with tips resting on food groove on floor of cavity. Male has wrinkled cylindrical penis with thickened tip 12Cc flic.kr/p/irNQXq that distends into bilobed swollen end during copulation .

 

Key identification features

Calyptraea chinensis

1) Patelliform cone with nearly central apex 3Cc flic.kr/p/irNA6H .

2) Nearly circular aperture with internal septum (shelf) 5Cc flic.kr/p/irNS4J .

3) Body translucent white, fawn-white or grey-white with flakes of opaque white 6Cc flic.kr/p/irNREY .

4) Very large whitish or yellow-white ctenidium 11Cc flic.kr/p/irNz5K .

 

Similar species

Patella spp. and other limpets.

2) Conical shell with no internal septum (shelf).

4) No ctenidium (Patella spp.) or small ctenidium (some other limpets).

 

Crepidula fornicata

1) Reniform vaulted shell with small depressed spire at one end 1Cf flic.kr/p/iHTKuN .

2) Reniform aperture with internal septum (shelf) 3Cf flic.kr/p/iHTJDj .

3) Usually, some parts of body blackish 6Cf flic.kr/p/iHTGNL .

4) Very large blackish ctenidium.

 

Habitat and ecology

Mainly sublittoral, but occurs at LWS on some sheltered shores Dorset-Cornwall and Channel Islands, locally common and gregarious. On shells and stones that are often little bigger than animal. When substrate is dense sediment, C. chinensis selects position raised clear of it to avoid clogging of ctenidium. Grips substrate with broad sucker-like foot. Remains stationary for long periods; when removed leaves shiny, but not excavated, adhesion mark. Will move short distances in breeding period.

One of only a handful of British gastropods** that feed like bivalves by filtering phytoplankton and suspended organic particles from the water; one of the most perfectly adapted to this mode of life. Strong transverse, left to right, respiratory current created by cilia covering very large ctenidium 11Cc flic.kr/p/irNz5K carries in large amounts of food material. Particles are trapped as water passes through ctenidium by porous mucus sheets on both its faces, and by pallial filter 10Cc flic.kr/p/irPqTk of mucus between left side of body and mantle edge. The sheets of mucus are constantly growing and being driven down the ctenidium to a ciliated food groove on the floor of mantle cavity where they and the adhering food are rolled into cylinders. The rolls are carried by cilia along the groove, past the base of the right neck lobe 12 Cc flic.kr/p/irNQXq to food pocket under mantle skirt by mouth. Another food groove on the left carries food to the pocket from the pallial filter 7Cc flic.kr/p/irNRnJ . Radula 7Cc flic.kr/p/irNRnJ licks sections of food roll into buccal cavity; minimal wear on teeth as diet exclusively soft.

Defence against attack provided by shell, and by repugnatorial glands embedded in mantle edge 8Cc flic.kr/p/irPraT that give off repellent protein in persistent threads when violently stimulated.

Breeding: Small males ride on larger older females while mating with substantial penis; in all months, peak Oct-April. During copulation, bilobed tip of penis distends to grip wall of upper end of pallial oviduct. Female spawns twice a year (April- September at Plymouth, December to May at Naples). Very soft, thin-walled, triangular, 3mm long capsules containing 12-24 ova each, laid April-September (Plymouth). Female holds capsules with front of foot for a time before attaching by thin end to substrate under anterior part of her shell in course of strong inhalent current. Ova concentrated in wide end of capsules. Female incubates them until, having passed the veliger stage within the capsules, the young emerge as crawling juveniles with embryonic spiral shell of one and a half coils.

C. chinensis is protandrous sequential hermaphrodite; all young are born as males and function as males through the first breeding season lasting 3-4months. Then remaining sperm absorbed, penis reduced and lost, and open-groove vas deferens closes to form oviduct as male changes to live on one or two years as a functioning female. Change is always at same development stage; not controlled by environmental factors or proximity of other C. chinensis individuals.

[**Other British gastropods known to filter feed: Crepidula fornicata, Turritella communis, Capulus ungaricus, Viviparus contectus, Bithynia tentaculata; last two in freshwater]

 

Distribution and status

C. chinensis is native to the Mediterranean and west Europe as far north as southern Britain. Its specific epithet refers to the shape of a stereotypical Chinese hat, not occurrence in China. The GBIF map at www.gbif.org/species/2301629 shows records scattered across the world. Some may be introductions with commercially translocated shellfish, but those located inland are certainly fossils or mistaken identifications or locations, and others may be also. In the British Isles it is most frequent, occurring sublittorally and littorally, on the south coast of England from west of Sussex to Cornwall, and in south-west Wales. Beyond that area, there are scattered sublittoral, and some littoral, records up the west coast as far as Shetland and in Ireland 14Cc flic.kr/p/2pfyq1s . Some may have been introduced accidentally by humans with translocated shellfish. U.K. distribution map NBN species.nbnatlas.org/species/NBNSYS0000174315

 

Acknowledgements

For use of images and information, I gratefully thank Paul Brazier and Jamie O’Neill.

 

References and links

Forbes, E. & Hanley S. 1849-53. A history of the British mollusca and their shells. vol. 2 (1849). London, van Voorst. (As Calyptraea sinensis ; Free pdf at archive.org/details/historyofbritish02forb Use slide at base of page to select pp.463-465)

 

Fretter, V. and Graham, A. 1962.British prosobranch molluscs. London, Ray Society.

 

Graham, A. 1988. Molluscs: prosobranch and pyramidellid gastropods. Synopses of the British Fauna (New Series) no.2 (Second edition). Leiden, E.J.Brill/Dr. W. Backhuys. pp.662.

 

Jeffreys, J.G. 1862-69. British conchology. vol.3 (1865) . London, van Voorst. (Free pdf at archive.org/details/britishconcholog03jeffr . Use slide at base of page to select pp272-276.)

 

Minchin, D. and Nunn, J.D. 2006. Further range extensions of the marine gastropod Calyptraea chinensis (L.) in Ireland. Ir. Nat. J. 28:5 200-203 www.jstor.org/discover/10.2307/25536712?uid=3738032&u... )

 

Wigham, G.D. & Graham, A. 2017. Marine gastropods 2: Littorinimorpha and other, unassigned, Caenogastropoda. Synopses of the British Fauna (New Series) no.61. (344 pages). Field Studies Council, Telford, England.

 

Yonge, C.M. and Thompson, T.E. 1976. Living marine molluscs. London.

 

Current taxonomy: World Register of Marine Species (WoRMS) www.marinespecies.org/aphia.php?p=taxdetails&id=138961

 

Glossary

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

cephalic – (adj.) of or on the head.

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

 

ciliated – (adj.) coated with cilia.

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

 

ELWS – extreme low water spring tide (usually near March and September equinoxes).

 

helical – spiral in three dimensions.

mantle – sheet of tissue that secretes the shell and forms a cavity for the gill in most marine molluscs. (also known as "pallium")

 

monopectinate – (of ctenidium) filaments only on one side of axis.

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

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

pallial - (adj.) of the pallium (alternative name for "mantle").

patelliform – shaped like the cone of limpets in genus Patella even when not closely related.

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

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

propodial - at the front of the foot.

 

protandrous – (of sequential hermaphrodites) born as male, changes later to female.

protogynous – (of sequential hermaphrodites) born as female, changes later to male.

 

reniform – kidney-shape outline.

septum – partitioning wall.

setose – bearing many setae.

seta – stiff hair or bristle. (pl. setae)

vas deferens – duct that carries sperm to penis.

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

 

Done