How do shellfish reproduce?
BRIAN TAM
Canadian International School
Shellfish include marine animals such as oysters, scallops, crabs and lobsters.
Oysters reproduce by releasing millions of eggs and sperm directly into the sea when the water reaches a certain temperature. Fertilisation is left to chance and happens in the water when the sperm manages to penetrate the egg. Once fertilised, the eggs develop into larvae within hours and swim around for about 21 days, eating plankton and bacteria. The larvae develops an 'eyespot' and 'foot'. When the larvae has found a suitable place to settle down and reach maturity, it attaches itself firmly to a surface with the foot.
The male crab has to mate with the female just after the female has moulted and when its new shell is still soft. The male clasps the female tightly while he deposits sperm in a receptacle in the soft shell. The female can store the sperm there and uses it later to fertilise eggs that are attached to its abdomen.
Scallops have the ability to produce both male and female sex cells. A change in water temperature can trigger spawning - the release of sperm and egg in to the sea. To avoid self-fertilisation, a scallop releases its eggs and sperm at different times.
