Mactra olorina

Mactra olorina
Mactra olorina (from Philippi, 1846: Mactra plate 2, Fig. 2)
Systematics
Superordinate : Imparidentia Order : Superfamily : Mactroidea Family : Trough clams (Mactridae) Genre : Mactra Type : Mactra olorina
Scientific name
Mactra olorina
Philippi , 1846

Mactra olorina is a shell - type from the family of white clams (Mactridae). The species originally endemic to the Red Sea is a Lessepsian immigrant in the south-eastern Mediterranean .

features

The same-flanged, slightly expanded housing is up to 6 cm long. The ratio of length to height to thickness is about 32:23:16. There is a little gap in the back. The forward curled vertebra sits roughly in the center line of the case to very slightly in front of the center line, i.e. H. the housing is almost equilateral. It is rounded-triangular in outline. The anterior and posterior dorsal edges are almost straight. The ventral margin is well arched. The front end is tightly rounded, the rear end is more tightly rounded. The ligament lies internally on a spoon-shaped extension of the shell ("chondrophor") under the vertebra. The lunula is oblong-egg-shaped. An area is available. The lunula and area stand out due to their darker color. The lock of the left valve consists of two main teeth and an anterior and posterior posterior tooth. The two main teeth form an inverted V-shaped structure. The right valve has two main teeth, the anterior one is almost parallel to the dorsal margin. and two anterior and posterior posterior teeth. The lower posterior teeth are longer than the upper posterior teeth and also protrude further. The surface line is only slightly indented.

The skin is thin and brittle. The color ranges from whitish to beige. Towards the vortex, the surface becomes lighter and lighter, the vortex area is white. From the vortex area, lighter rays move radially to the edge of the housing. The surface shows fine, closely spaced growth strips parallel to the edge at regular intervals and approximately the same thickness, which, however, are somewhat more pronounced in the front part of the case than on the rear part of the case. The surface is shiny. The inner edge of the case is smooth. The periostracum is thin.

Similar species

The species can be confused with Mactra lilacea , also a Lessepsian immigrant from the Red Sea in the southeastern Mediterranean. With Mactra olorina , however, the ornamentation in the front part of the case is much stronger than in the rear part of the case. In addition, with Mactra lilacea the growth strips are at irregular intervals, with Mactra olorina they are much more regular. The vertebral area is white, whereas in Mactra lilacea it is purple-brown.

Geographical distribution, habitat and way of life

The species was originally endemic to the Red Sea. The species was found in the Suez Canal and Port Said ( Egypt ) as early as the end of the 19th century . It is very common in the Bardawil Lagoon in the Nile Delta. It is less common along the coast of the Sinai Peninsula , Gaza Strip , Israel, and the coast of Lebanon .

The animals live buried in sandy or muddy soils in shallow water to a depth of around 50 meters. They are suspension filter feeders.

Taxonomy

The species was first described in 1844 by Rudolph Amandus Philippi as Mactra cygnea . However, the name is preoccupied by Mactra cygnea Spengler, 1802. Philippi replaced the name with Mactra olorina in 1846 . The MolluscaBase lists the following synonyms : Mactra isthmia Jousseaume, 1888, Mactra semisulcata Deshayes, 1854 and Mactra striata Spengler, 1802. The latter name is a younger homonym of Mactra striata Gmelin, 1791.

supporting documents

literature

• Peter Graham Oliver, Kevin Thomas (pictures): Bivalved seashells of the Red Sea. 330 pp., Wiesbaden, Hemmen et al. a., 1992 (p. 131)
• Argyro Zenetos, Serge Gofas, Giovanni Russo, José Templado: CIESM Atlas of Exotic Species in the Mediterranean. Vol.3 Mollusca. CIESM (Frédéric Briand, ed.), Monaco, 2003 (p. 278/79)

Individual evidence

1. ↑ ^{a b} Rudolph Amandus Philippi: Illustrations and descriptions of new or little known conchylia. Second volume. 1–231 p., Taf. 1–48, Cassel / Kassel, printed and published by Theodor Fischer, 1846-47. Online at www.biodiversitylibrary.org (p. 74 scan incomplete!) Or online at Google Books Mactra plate 2
2. ↑ Rudolph Amandus Philippi: Descriptiones testaceorum quorundam novorum, maxime chinensium. Zeitschrift für Malakozoologie, 1: 161–167, Hannover 1844 Online at www.biodiversitylibrary.org (p. 161/62)
3. ↑ MolluscaBase: Mactra olorina Philippi, 1846