How do mussels and oysters reproduce?

Mussels and oysters belong to the phylum Mollusca, class Pelecypoda. They lack a head and have a hatchet-shaped foot for burrowing. Their sexual reproduction is hermaphroditic, which means that each animal has both sexes. Two animals come together in copulation, each inseminating the other. Self-fertilization is prevented by the development of the testes and ovaries at different times. Oysters and mussels are first male, then female. (And you thought humans were weird.)