Aspalima cristata

Aspalima cristata
Aspalima cristata (from Jeffrey 1879: Plate 46, Fig. 8)
Systematics
Pteriomorphia Order : Arcida Superfamily : Limopsoidea Family : Limopsidae Genre : Aspalima Type : Aspalima cristata
Scientific name
Aspalima cristata
( Jeffreys , 1876)

Aspalima cristata is a shell - type from the family of Limopsidae in the order of Arcida .

features

The same-flattened, flattened case has a maximum length of 10 mm (11 mm: Oliver & Allen). It is slightly obliquely egg-shaped as an adult, the rear part of the housing is moderately elongated. Juvenile housings, on the other hand, are rounded. The adult housing is therefore also slightly unequal, and the small, slightly forward-curled vertebrae sit in front of the center line of the housing. It's about as tall as it is long. The dorsal margin is straight, the front and rear dorsal margin are about the same length. The posterior dorsal margin merges with the broadly rounded posterior margin at a very flat angle. The transition from the anterior dorsal margin to the anterior margin is also very flat-angled, only very slightly steeper than the posterior transition. The front edge is slightly less arched than the rear edge. In the subspecies Aspalima cristata affinis the leading edge is almost straight. The ventral margin is well arched. The dorsal field between the vertebrae is sunk flat.

The ligament is narrow-rhombic and extends on both sides of the vertebra. The resilium is small and triangular. It sits in a shallow pit (resilifer) between the vertebrae. The taxodontic lock plate is wide; the upper edge is straight, the lower edge slightly curved. The lock consists of two series of strong, straight to slightly curved teeth that are separated from each other by a toothless area. In both series there are five to eight small teeth that diverge slightly outwards. The two sphincters are unequal in size. The anterior sphincter is less than half the size of the posterior sphincter. This sits slightly above the middle of the rear edge, while the front one sits directly below the front end of the lock plate. The surface line is not indented.

The aragonitic skin is thin but not brittle. The ornamentation consists of radial lines that are crossed by concentric lines. This creates a net-like pattern that is usually hidden by the periostracum. The straw-yellow to yellow-brown periostracum is drawn out into bristles that are arranged in lines and protrude upright. In the subspecies Aspalima cristata affinis , the periostracum bristles are stiffer and longer; the arrangement in radial lines is more pronounced than in the nominate subspecies. The shell itself is whitish, the inner surface is whitish-shiny. The inner edge of the case is notched.

Geographical distribution, habitat and way of life

Aspalima cristata has a large distribution area along the eastern North Atlantic from Ireland to the Iberian Peninsula . It has been found in the western North Atlantic from Cape Cod ( Massachusetts ) to Florida . It is also found in the Gulf of Mexico .

The animals live half buried and attached to sediment particles with a few byssus threads on the continental slope at a depth of around 500 to 2000 meters. They are suspension filter feeders.

Taxonomy

John Gwyn Jeffreys described the species for the first time in 1876 under the binomial Limopsis cristata . Three years later he also provided an illustration. The species is now part of the genus Aspalima Iredale, 1929.

Oliver & Allen adopted three subspecies in 1981, Limopsis cristata cristata , Limopsis cristata affinis Verrill, 1885, Limopsis cristata intermedia nov. subsp. and Limopsis cristata lanceolata nov. subsp. on. Only Limopsis cristata affinis Verrill, 1885, is recognized today as a subspecies of Aspalima cristata in addition to the nominate subspecies . The other two subspecies are separate species in the genus Aspalima Iredale, 1929.

literature

• Fritz Nordsieck : The European sea shells (Bivalvia). From the Arctic Ocean to Cape Verde, the Mediterranean Sea and the Black Sea. 256 p., Gustav Fischer Verlag, Stuttgart 1969 (p. 27/28)
• Graham Oliver, John A. Allen: The Functional and Adaptive Morphology of the Deep-Sea Species of the Family Limopsidae (Bivalvia: Arcoida) from the Atlantic. Philosophical Transactions of the Royal Society of London Series B. 291: 77-125, 1980 JSTOR .

Individual evidence

1. ^ ^{A b} John Gwyn Jeffreys: On the Mollusca procured during the 'Lightning' and 'Porcupine' Expeditions, 1868-70. (Part II.). Proceedings of the Zoological Society of London, 1879: 553-588, 1879 Online at www.biodiversitylibrary.org (p. 585), plate 46
2. ↑ ^{a b c} Marine Bivalve Shells of the British Isles: Limopsis cristata (Jeffreys, 1876) (website of the National Museum Wales, Department of Natural Sciences, Cardiff)
3. ↑ Donna D. Turgeon, William G. Lyons, Paula Mikkelsen, Gary Rosenberg, Fabio Moretzsohn: Bivalvia (Mollusca) of the Gulf of Mexico, In: Felder, DL, DK Camp (eds.): Gulf of Mexico-Origins, Waters , and Biota. Volume 1 Biodiversity . Pp. 711-744, Texas A&M University Press, College Station, Texas 2009 PDF (ResearchGate).
4. ^ John Gwyn Jeffreys, New and peculiar Mollusca of the Pecten, Mytilus and Arca families, procured in the Valorous expedition. Annals and Magazine of Natural History. 4. series, 18: 424-436, London 1876. Online at www.biodiversitylibrary.org (p. 434)
5. ↑ ^{a b} MolluscaBase: Aspalima cristata (Jeffreys, 1876)