Snails Sea Slugs and Limpets: Gastropoda

Like most animals, gastropods must feed, fight, flee, and mate. To do all this they have developed many different behaviors. Most species sense their world through the presence of certain kinds of chemicals produced by their foods and other members of their own species. Aquatic species regularly move up and down in the water at certain times of the day in search of food and mates. Depending on the species, they may become active during the day or at night, whenever they are least likely to be attacked by predators.

Gastropods usually require both males and females to reproduce, although some species are hermaphroditic (her-MAE-fro-DIH-tik). Hermaphroditic individuals either have the reproductive organs of both sexes at the same time or start out as males and later become females. In most species, the males transfer sperm, or packets of sperm, directly into the female's reproductive system. The sperm is stored in a special sac. Fertilization takes place only when the eggs are laid. The eggs are laid or released individually or in groups. The eggs of species living in water usually hatch into larvae (LAR-vee) known as veligers (VEL-ih-jerz). The veliger has a special, round feeding organ lined with hairlike cilia (SIH-lee-uh) that it also uses for swimming. It also has a foot, shell, and other adult features. During this stage a single, powerful muscle, usually permanently twists the body and shell, if present. In some snails, including those living on land, the veliger stage takes place inside the egg, which then hatches into a tiny version of the adult.