Sea scallops reproduce through spawning. Some scallops have male and female reproductive capabilities, while others produce only eggs or sperm cells. During spawning, the scallops release large quantities of eggs and sperm into the water. Fertilized eggs quickly develop into tiny scallops that are suspended in the water like plankton. They soon develop hard shells and spend the rest of their lives on the ocean floor.
Most bivalve species reproduce by spawning, although the process varies considerably between species. For example, certain clams use a hybrid spawning technique that involves releasing sperm cells into the water column. Females suck the sperm-rich water into the area of their bodies where their eggs await fertilization. The fertilized eggs remain inside the shell until they become larvae.
During the larval stage, most bivalves consume phytoplankton and diatoms. Some species also derive nutrition from a yolk sac filled with a fatty, nutrient-rich compound. Those with large yolks depend entirely upon them until their shells grow, but species with smaller yolks supplement their diet with plankton.
Mature bivalves rely on their shells as a primary source of shelter and protection. Once the shell forms, the creatures attach themselves to rocks, the sea floor, sunken ships or similar hard surfaces. Unlike immobile bivalves, scallops can swim. They do this by drawing water inside their shells and forcefully ejecting it, which propels them in the opposite direction.