Reproduction Reproduction Enclosed in shells and buried, most Bivalves can't seek out mates, as Gastropods commonly do. Instead, males and females synchronously spawn millions of sperm or eggs through the exhalant siphon.
External fertilisation occurs when sperm randomly encounter eggs in the water column.
The fertilised egg develops into a shell-less trochophore larvae, then into a miniature bivalved veliger larvae. Soon the veliger larvae drops to the bottom, anchors to a stone or coral by a byssal thread , and transforms into the adult animal.