Ostrea Lurida - Reproduction

Reproduction

The Olympia Oyster spawn between the months of May and August, when the water reaches temperatures above 14 degrees Celsius. During the oyster's first spawning cycle they will act as a male and then switch between sexes during their fallowing spawning cycles. The males release their spermatozoa from their mantle cavity in the form of sperm balls. These balls dissolve in the water into free floating sperm. The female's eggs are fertilized in the mantle cavity (brooding chamber) when spermatozoa are filtered into her gill slits from the surrounding water. The fertilized eggs will then move into the branchial chamber (mantle cavity). The fertilized eggs will develop into veliger larvae and will stay in the females mantle cavity for 10–12 days for further development. On the first day the larvae develop into a blastulae (mass of cells with a center cavity), on day two they develop into a gastrulae (hollow two layered sac), on the third day they develop into trochophore (free-swimming, conciliated larvae), on the fourth day the valves on the dorsal surface become defined. During the rest of development in the brooding chamber the valves complete and a straight-hinged veliger larva grows.

When the spat (larvae) leave the brooding chamber, they begin to develop an eye spot and a foot. They then migrate to hard surfaces (usually old oyster shells) were they attach by secreting a "glue" like substance from their byssus gland. Ostrea lurida spat swim with their foot superior to the rest of their body. This swimming position causes the larvae to attach to the underside of horizontal surfaces.

Brood size is between 250,000-300,000, with larvae around 187 micromillimeters long and eggs around 100-105 micromillimeters in diameter. The amount of larvae produced is dependent on the maternal oyster's size and the amount of reserved nutrients she has at the time of egg fertilization.