Freshwater mollusc

Freshwater molluscs are those members of the phylum Mollusca which live in freshwater habitats, both lotic (flowing water) such as rivers, streams, canals, springs, and cave streams (stygobite species) and lentic (still water) such as lakes, ponds (including temporary or vernal ponds), and ditches.

Large rivers and small tributary creeks typically share few species, and distribution patterns suggest large lowland rivers represent substantial barriers to the dispersal of species adapted to small upland streams.

In contrast, some of the tiny pill clams have a nearly worldwide distribution (Burch, 1972)[1] Challenges in the natural environment faced by freshwater Mollusca include floods, droughts, siltation, extreme temperature variations, predation, and the constant unidirectional flow characteristic of river habitats.

Osmoregulation, or the maintenance of constant salinity within body tissue and fluids, is another challenge faced by freshwater Mollusca.

Some freshwater snail species serve as hosts for human and animal parasites.