Freshwater snails are widely distributed across the world. There are over 600 species of freshwater snails in ponds, lakes and rivers in the United States. Snails are an important part of freshwater ecosystems.
They provide food for other animals, such as fish, frogs, birds and crayfish. They feed on algae thereby controlling algae growth, especially in ponds. Apple snails are sold in many aquarium stores, and people interested in breeding apple snails need one male and one female.
Female freshwater snails are usually larger and heavier than males of the same species. Some males have a distinct sex organ that protrudes from an area in front of the gills. In some species, the males are indistinguishable from females apart from physical size. Freshwater snails that have an operculum, or hatch-like covering over the opening in their shell, have separate sexes. Most freshwater snails in North America have an operculum. Snails that do not have an operculum have both male and female reproductive organs.
Snails reproduce by copulation. The male snail crawls onto the shell of the female snail and holds her shell with his foot during the fertilization process. Snails that possess both male and female sex organs also copulate. These snails exchange male sperm which they then use to fertilize their eggs. Snails with both male and female reproductive organs do not self-fertilize with their own sperm. Fertilization can last one hour to one day. Many females can store sperm for many months.
Female freshwater snails lay eggs in clutches usually above the water line or on the underside of leaves. One female can produce as many as 600 eggs in one clutch. In their natural habitat, freshwater snails found in temperate regions lay eggs from spring to fall. Freshwater snails in warmer environments may lay eggs year round. The eggs hatch in about three weeks, or sooner if the weather is warm. Baby snails are able to eat algae and forage as soon as they hatch.
Freshwater snails in the vivipariidae family give birth to live baby snails. After fertilization, the female snail keeps her eggs inside a special cavity in her body where they are protected. The eggs hatch inside her where the baby snails feed inside the mother’s body. The young snails crawl out of the mother’s cavity when they have consumed the stored nutrients and reach about 1/4-inch long. The female snail may incubate as 10 to 12 eggs inside her body at once.