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Life in Freshwater

Nerite Snails (Theodoxus fluviatilis)

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Theodoxus snail

IDENTIFICATION: up to a centimetre long. The shell is distinctly mottle white, some say like a chess board. Found in a variety of habitats from swift flowing stoney rivers to stoney lakesides and even in brackish water. It seems to be associated with "hard" water, so chalk streams as well. Theodoxus is the only snail of this type, i.e. a nerite. Related to the periwinkles of seashores. Operculate snails are those with a "trap door" or "lid" to the shell attached to the back of the foot.

ECOLOGY: this snail has both males and females. Eggs are laid in small white capsules of about 1 mm. These form white dots on stones and plants. The capsule or cocoon is made of a chitinous material to protect them. This is unusual for freshwater snails as most produce a stream of jelly to suspend the eggs from the vegetation.The capsule contains around 80 eggs but as the first one hatches it eats the remaining ones. They live on the bottom feeding upon both decaying and living vegetation. This is a herbivore feeding on the growing vegetation in the river. It is well camouflaged and difficult to see even though it may be common.

See also Great Pond Snail, and Spire Shells










Operculate snails

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