The diversity of storage tissue cell types in bivalve molluscs is evident. In some species there are no specific storage cells, and the adductor muscle plays the role of a reserve tissue (Pectinidae). In others both muscular cells and specific storage cells are involved in storage and release of nutrients for gametogenesis (Veneridae). A few species have a specific storage tissue such as the mantle inMytiluscontaining two complementary types of cells. This specialisation can be correlated with the fertility of the species and with the variation of available food organisms. Vesicular connective tissue is found in species with a high level of fecundity which are subject to marked fluctuations in food availability (Mytilidae, Ostreidae). This can be considered as an adaptive behaviour to profit from uncertain supply of food supplies in order to produce the maximum number (and quality) of gametes in a precise period of the year.