Ordering set seed is more expensive but a little less risky, and, depending on the seed size and growing methods, means a product to market in less time. Larvae Technically speaking, bivalves that have not yet metamorphosed and set are called larvae. Oyster larvae for example will set at somewhere between 16 and 20 days post-fertilization. Setting happens when the oyster contacts a suitable surface with its foot, a gland secretes cement and the left valve is attached. Once this process is complete, they are usually referred to as seed.
Clams undergo a slightly different process.
Velum and foot probing activity indicate readiness to set but unlike the oyster, the clam has no visible eyespot. When it is ready to metamorphose, the velum is lost and with it the ability to swim. The clams search available surfaces and move around by the foot until a suitable spot is found. Then a byssal thread is secreted and the calm attached. If it does not like the chosen spot it can sever the thread and move to a new spot.