Donacilla cornea (Poli, 1791)
Synonyms: Mactra cornea Poli, 1791; Donax elliptica Krynicki, 1837; Mesodesma donacilla Middendorff, 1849; Mesodesma cornea (Poli) Ostroumoff, 1893.
Common names: None.
Order (Scientific): VENERIDA.
Family (Scientific): MESODESMATIDAE.
Taxonomic descriptions: Shell flattened, elongated, triangular, with small umbo, but prominent and slightly curved forward, without ribs; thin periostracum; the surface of the shell is smooth with fine concentric lines and discrete growth striations; background colour yellowish-white with rare brownish radiating pigmentary striations; some specimens have yellowish, reddish or mauve pigment. Size: length - 20-24 mm; width - 8 cm.
Black Sea Regional level: EN
Subregion level: EN (Ukrainian sector)
Habitats type, Critical habitats, Limiting factors: Inhabits coarser sands in the midlittoral, sometimes in the phreatic of supralittoral sands. Present in the Azov Sea, Mediterranean Sea and along the European coasts of Atlantic Ocean, north to England. Modifications in the structure of substrata due to hydrotechnical works; turbidity caused by sand extraction.
Biology: This species has no planktonic larvae, these are incubated in the paleal cavity of the female as an adaptation to the semiliquid environment in which they leave.
Population trends: On the Crimean littoral, densities of more than 3,000 individuals/m2 were found in the 1950s. On the southern Romanian littoral, it was frequent till 1975-1980, in the coarser sand littoral, forming a specific community together with Ophelia bicornis polychaeta, both forms prevailing in the midlittoral fauna with coarser sands (up to 10,000 ind/m2). After 1980 it became extremely rare, and in the last decade it has not found at all.
Threats: Changes in the granulometric structure of sand through the closing the interstitial spaces of coarse sand.
Conservation measures taken: None.
Conservation measures proposed: Prohibit sand extraction from sandy beaches; reduce pollution.
Compiled by: M.Gomoiu, A.Petranu.