Left-handed pond snails
Class Gastropoda: Subclass Pulmonata: Order Basommatophora.
A near-cosmopolitan family but one which does not appear naturally in Australia. Most Australian left-handed (sinistral) pond snails belong in the family Planorbidae.
The northern European Physa acuta is an introduced physid known from south-east Australia, South Australia and Tasmania. It occurs in slow to non-flowing water where it feeds on decaying leaves. To separate this species from some left-coiled members of Planorbidae it is necessary to dissect out the radula (mouthparts). The radula teeth are arranged in transverse rows in the Planorbidae, but in chevroned rows in the Physidae.
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.