First study of the life cycle of Pisidium tenuilineatum Stelfox, 1918 (Bivalvia, Sphaeriidae)

The sampling of molluscan communities in the French Upper Rhône has permitted describing the life cycle of P. tenuilineatum. This small bivalve gives birth to two or three generations per year that emerge from May to September. The presence throughout the year of gravid individuals and newborns suggests that each individual reproduces sever - al times during its lifetime (iteroparity) of one to two years. In European Pisidium this reproduction strategy has only been observed in populations of P. conventus living in deep zones of lakes. However, it does not appear to endow P. tenuilineatum with any particular advantage since it is most usually represented by only small populations.