The biology of reproduction of Venus gallina L. (Lamellibrachia) in the Black Sea

In the Black Sea Venus gallina L. is a mass form; however its biology, namely reproductive biology, has been insufficiently studied. V. gallina occur also in the Mediterranean Sea and the Atlantic Ocean; some researchers consider Atlantic form of the mollusc as species V. striatula de Costa (Forbes and Hanley, 1853) while some other suppose that V. striatula is only a variety of V. Gallina (Jeffrey, 1867; Bucquoy, Dutzberg et Dollfus, 1882; Eales, 1939). This species have evolved aving evolvedHmorphological forms special for different parts of the vast geographic area, therefore it is interesting to compare the biology of reproduction typical of Atlantic and Black sea forms. Our investigation has shown that Black sea and Atlantic V. gallina have similar annual cycle of gonad development: the distinct cycle develops without resting stage, gametogenesis starting immediately after spawning. But spawning time and temperature are different: near the shores of Scotland V. striatula (=V. gallina) spawn in late May, when the seawater temperature is 9-11°С whereas in the Black Sea reproduction of V. gallina begins in summer, when the sea warms to +20-21°С. Based on the critical spawning temperature, Atlantic and Black sea forms of V. gallina are, presumably, two different physiological races like those known for oysters Ostrea virginica (Loosanoff and Davis, 1952) and Ostrea edulis (Korringa, 1957), or even two different species