Reproduction in Australian Pearl Oysters (Lamellibranchia). III. Pinctada albina (Lamarck): Breeding Season and Sexuality

Abstract

Plnctada albina breeds continuously throughout the year, but most actively during April and May when sea temperatures begin to fall. Thus the species resembles the majority of tropical marine invertebrates in the former respect but differs from them in the latter. The heaviest spatfalls occur from June to August when sea temperatures are at a minimum. This species is hermaphrodite, with a, general tendency toward protandry. Both male-female and female-male sex changes, and the bisexual condition which sometimes prevails during change-over, have been observed. Sex change in bivalves is discussed, and it is suggested that the phenomenon can best be explained in terms of a weak hereditary sex-determining mechanism, and germ cell rudiments responsive to the food reserve level in the body such that male differentiation is favoured at lower levels and female differentiation at higher levels.