Right-handed pond snails
Class Gastropoda: Subclass Pulmonata: Order Basommatophora.
An almost-cosmopolitan family of snails. Most species inhabit standing freshwater, or stagnant water, but some are found in other aquatic habitats including mildly saline conditions. The family is widespread, occurring both on the Australian mainland and in Tasmania. The family includes several species common as aquarium snails, and some escapes may be expected (Kershaw, 1991). Five species in three genera are recorded from Australia with at least three species introduced.
Lymnaeids are potentially of major economic importance as some species are the main intermediate hosts for sheep liver fluke ( Fasciola hepatica ). Two species are known major vectors of Fasciola : Austropeplea tomentosa, native to Australia and New Zealand, and Pseudosuccinea columella , introduced from North America.
The common 'pond snails' that live in managed pastoral farm dams and drains include lymnaeids and planorbids and physids. In view of the restriction of fluke transmission to species of lymnaeids, these must be separated by recognising their dextral shell and wide triangular tentacles, in contrast to the sinistral shells and narrow tentacles of planorbids and physids.
Lymnaeids also may need separation from the land snail family Succineidae, which can be found along damp margins of aquatic habitats. Smith (1996) observes that in live specimens of lymnaeids the tentacles are fleshy and triangular with the eyes at the base of the tentacles. In contrast, the succineid tentacles are cylindrical with the eyes at the tips.
Lymnaeid shells often vary markedly with habitat, tending to be shorter in running waters and thicker in more calcareous waters. Temperature and food type can also be important to growth form. Morphological variation is further accentuated by the fact that parthenogenetic individuals regularly give rise to distinct, localised populations. These factors make for taxonomic problems and the family contains many more species names than there are valid species.
Kershaw, R.C. (1991) Snail and slug pests of Tasmania . Queen Victoria Museum and Art Gallery, Launceston.
Smith, B.J. (1996) Identification keys to the Families and Genera of Bivalve and Gastropod Molluscs found in Australian Inland Waters . Cooperative Research Centre for Freshwater Ecology Identification Guide No. 6., Albury, NSW.