The life cycle of the oyster

Before reaching adulthood, the oyster goes through various stages of development.

Illustration of the oyster's life cycle

Egg cell and cell division

Upon fertilization between the ovum and spermatozoon, cell division begins. 

Larva Trochophore

The Trochophore larva is a ciliated larva that moves by spinning around itself. It's the first larval stage of the oyster. It forms after 6 hours and has a pelagic life (it lives in open water).

Larva D

The Larva D appears after 24 hours. It's named this way because of its very particular shape: it resembles the capital letter "D". This "D" corresponds to the future shell of the oyster. It serves as a guide for the shell that will form on it. It still has cilia but also a velum that enables its movement. This velum will be fully formed in the veliger larva (the next stage in its cycle).

Veliger Larva

The Veliger larva is still pelagic. At this stage, its cilia and velum (which completes its formation) allow it to more easily capture its food (phytoplankton cells). The definitive shell begins to form, as well as the hinge, which will allow the adult to open and close its valves.

Pediveliger Larva

The Pediveliger larva is the last stage before its benthic life (at the bottom of the sea). This phase marks the appearance of the foot and a black spot on the shell (eyed larva). This spot heralds the metamorphosis, which occurs in two stages:

• Firstly, the larva falls to the bottom to find a suitable substrate. If the place doesn't suit it, it resumes swimming until it finds a suitable substrate.
• Secondly, it involves the larva's definitive fixation on its substrate, where it will grow to become spat, then an oyster.

Spat

After this metamorphosis, the larva becomes a micro-spat, then a spat.

The spat is raised for about 2 and a half years to reach adult size. This adult oyster then becomes marketable.