Gonad Maturation And Sexuality In The West African Bloody Cockle, Anadara Senilis
Abstract
Gonad maturation and sexuality in Ghanaian populations of Anadara senilis were studied by means of macroscopic examination of the visceral mass, microscopic examination of smears of sexual products and by histological methods. Sexual differentiation into either distinct male or female, begins at a shell length of 10-12mm. Only 1% or less have both ovary and testis. First spawnings take place at shell size 18-20mm. Although in tidal lagoons the sex ratio is 1:1, in the adverse conditions of closed lagoons, the male to female ratio is about 1:2. Unbalanced sex ratios recorded in a population in Lagos, Nigeria, led a previous worker to the conclusion that the species is a protandric hermaphrodite. It is argued here that hermaphroditism is an insignificant feature in A. senilis and that the species is basically gonochoristic (dioecious).
