The Horse Clam Smaller of body and neck the Horse clam is a relative of the Geoduck. Mass fertilization occurs in water column. Fertilized eggs develop rapidly into ciliated larvae .
Larval phase includes several stages.
As the Larvae develop they drift in the plankton and are dispersed by water currents. The larval phase ends when larvae settle from the plankton and attach themselves to gravel or broken shell by byssal threads, as setting. The spat or juvenile clam creates a permanent burrow where it remains for life. Adult clams may live to 25 years and reach a maximum shell length of 8 inches. Adults can weigh up to 4 lbs.