Senilia senilis

Senilia senilis
	Senilia senilis
Systematics
Order :	Arcida
Superfamily :	Arcoidea
Family :	Ark clams (Arcidae)
Subfamily :	Anadarinae
Genre :	Senilia
Type :	Senilia senilis
Scientific name of the genus
	Senilia
	JE Gray , 1842
Scientific name of the species
	Senilia senilis
	( Linnaeus , 1758)

Senilia senilis (Linnaeus, 1758), from Kobelt (1891: Plate 9, Fig. 1,2)

Senilia senile is a shell - type from the family of ark shells (Arcidae) in the order of Arcida . It occurs in the tropical part of the eastern Atlantic in strongly tidal areas of the coastal waters there. It is currently the only species and type species of the genus Senilia Gray, 1847.

features

Even in early ontogenetic stages, the strongly flared housing, which has the same flaps, becomes up to 13.5 cm long, usually around 8 to 10 cm. Wilhelm Kobelt gives a ratio of length: height: thickness of 10: 8-9: 6. It is rounded-triangular in outline and usually clearly unequal; the vertebrae are in the front third of the length of the case. The case is usually longer than it is high, but the length / width ratio is also variable. There are also specimens that are almost as tall as they are long, and less unequal, i.e. H. the vertebrae sit in the front half of the case, but near the center. The straight dorsal margin is short and angled at both ends. The angle to the front edge is flat, the front edge is well rounded. The angle to the rear edge is even flatter and merges into the rear edge, which initially slopes down straight at 30 ° to 65 ° and even slightly concaves. The middle part is often set off from the upper part by a flat angle. It goes straight to very slightly rounded into the tightly rounded angle between the rear edge and the ventral edge. The ventral edge is well rounded and merges into the more closely rounded front edge without a noticeable step.

The vertebrae are twisted forward and clearly protruding. The area is very large and significantly wider in the front half. The ligament takes up a large part of the area, is pointed ovoid and wider in the front part. In the early ontogenetic stages it is still opisthodic (behind the vertebra), only in large, adult specimens then amphidic (on both sides of the vertebra).

The lock plate is wide or high and the taxodontic teeth are relatively long. The teeth are often a little bent or angled in the outer area. A sloping pit just below the vertebrae separates the front set of teeth from the back set. The front and rear set are unequal in width, the front set with up to 15 teeth is significantly shorter, often only half as wide. But the teeth are narrower, in the back set there are up to 16 teeth. No byssus slot has been developed.

The skin is very thick and firm. The housings are therefore very heavy for their size. The skin is whitish to dirty whitish on the outside, pure white on the inside. The outer ornamentation consists of 10 to 15 (12) radial ribs with narrow spaces. The ribs are broad, flattened and smooth on top. In shorter and relatively taller specimens, the ribs are somewhat narrower, more rounded at the top and more prominent. They run out at the front and rear ends. The red-brown to black-brown periostracum is smooth, thin and persistent; H. hardly flakes off. The inner edge has strong indentations that correspond to the ribs on the outside. Here, too, the notches towards the upper part of the rear edge become weaker and disappear completely. The two sphincter scars are roughly the same size.

Geographical distribution and habitat

The distribution area of the species extends from the Western Sahara (Rio de Oro) to Angola and São Tomé ( São Tomé and Príncipe ).

The animals live buried in fine sand, silty and sandy-muddy soils of estuaries, mangroves and open or almost closed lagoons in the tidal area. These habitats are also exposed to regular, seasonal changes in salinity. The species can be found in abundance here. In these areas it is often associated with Tagelus adansonii . During the rainy season, the salinity in these habitats can drop sharply due to the influx of fresh water. From 15 ‰ salinity, the animals close their valves, as fresh water is lethal for the animals for a long time.

Taxonomy

The taxon was set up as Arca senilis by Carl von Linné as early as 1758 . It is the type species and, according to MolluscaBase, the only species of the genus Senilia Gray, 1847. Markus Huber assigns a second species, Senilia subnitens Récluz, 1851, to the genus . The genus and species are generally recognized. MolluscaBase also lists the following synonyms: Arca cor Mörch, 1853, Arca grandaeva Röding, 1798 and Arca subnitens Récluz, 1851. Huber regards the latter species as a valid species.

Senilia senilis in a market in Senegal

commercial use

In many parts of the west coast of Africa, this species is the most commercially important species of ark mussel. It has been intensively collected and consumed there since prehistoric times. In Angola it is also used as a fishing bait. The empty flaps are used as road paving, fastening railway lines and for burning slaked lime. In Sierra Leone they are also used for the production of handicrafts.

literature

Kent Carpenter, Nicoletta De Angelis: The Living Marine Resources of the Eastern Central Atlantic. Volume 2 Bivalves, gastropods, hagfishes, sharks, batoid fishes, and chimaeras. Food and Agriculture Organization of the United Nations, Rome, 2016 (FAO Species Identification Guide for Fishery Purposes) PDF , p. 695.
P. Graham Oliver, Rudo von Cosel: Taxonomy of Tropical West African Bivalves. IV. Arcidae. Bulletin du Muséum national d'Histoire naturelle du Paris, 4th series, secion, 14A (2): 293–381, Paris 1992 PDF , here pp. 356–359.

Web links

Commons : Senilia senilis - Collection of images, videos and audio files

Individual evidence

↑ ^a ^b Wilhelm Kobelt: The genus Arca L. In illustrations according to nature with descriptions. Systematic Conchylia Cabinet by Martini and Chemnitz, 8 (2): 1-238, Nuremberg 1891 Online at www.biodiversitylibrary.org (p. 15/16), plate 9 .
^ Carl von Linné: Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Editio decima, reformata. (10th revised edition), Vol. 1: 824 p., Laurentius Salvius, Holmiae / Stockholm Biodiversity Heritage Library , p. 694.
↑ ^a ^b MolluscaBase: Senilia senilis (Linnaeus, 1758)
^ Markus Huber: Compendium of bivalves. 901 S., Hackenheim, ConchBooks, 2010, ISBN 978-3-939767-28-2 , here p. 135 (left fig., 2nd row from above), p. 566.

[Kobelt-1] Wilhelm Kobelt: The genus Arca L. In illustrations according to nature with descriptions. Systematic Conchylia Cabinet by Martini and Chemnitz, 8 (2): 1-238, Nuremberg 1891 Online at www.biodiversitylibrary.org (p. 15/16), plate 9 .

[Linnaeus-2] Carl von Linné: Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Editio decima, reformata. (10th revised edition), Vol. 1: 824 p., Laurentius Salvius, Holmiae / Stockholm Biodiversity Heritage Library , p. 694.

[MolluscaBase-3] MolluscaBase: Senilia senilis (Linnaeus, 1758)

[Huber2010-4] Markus Huber: Compendium of bivalves. 901 S., Hackenheim, ConchBooks, 2010, ISBN 978-3-939767-28-2 , here p. 135 (left fig., 2nd row from above), p. 566.