Physa acuta can be distinguished by its completely smooth shell and mottled mantle which can usually be readily seen through the semi-transparent shell. The animal has digitations (finger-like processes) along the mantle edge against the columella and there is no false gill (pseudobranch). Unlike planorbids, the animal, if damaged when alive, does not produce red blood.
Physa acuta Draparnaud, 1805
Common name: Acute bladder snail, fountain snail
Class Gastropoda
Infraclass Heterobranchia
Megaorder Hygrophila
Order Lymnaeida
Superfamily Planorboidea
Family Physidae
Subfamily: Physinae
Genus Physa Draparnaud, 1801 (Type species Bulla fontinalis Linnaeus, 1758) (Synonyms Physella Haldeman, 1842 (Type species Physa globosa Haldeman, 1842); Haitia Clench & Aguayo, 1932 (Type species: Physa (Haitia) elegans Clench & Aguayo, 1932). For a list of additional synonyms see http://www.marinespecies.org/aphia.php?p=taxdetails&id=160462).
Original name: Physa acuta Draparnaud, 1805. In Draparnaud, J. P. R. (1805). Histoire Naturelle des Mollusques Terrestres et Fluviatiles de la France. Paris : L. Colas, i-viii, 1-164 pp.
Type locality: Garonne River, France (introduced from North America).
Synonyms: Lymnaea heterostropha Say, 1825 and several others - see http://www.marinespecies.org/aphia.php?p=taxdetails&id=234093
This introduced species is often referred to as Physella acuta or sometimes Haitia acuta in the literature. Taylor (2003) transferred Physa acuta to the genus Haitia Clench & Aguayo, 1932 and this was followed in an earlier version of this key.
On water weeds, rocks, wood and other vegetation in rivers, streams, ponds, swamps, drains, ditches and similar habitats. Very pollution tolerant and may even be found in sewerage treatment plants. Often abundant. Feeds on algae and detritus. Egg mass a kidney-shaped jelly strip containing many small eggs. Development direct.
P. acuta is the host of the fluke Choanocotyle hobbsi in the Murray-Darling system (Barton et al. 2022).
Worldwide. Native to north-eastern United States and adjacent Canada. P. acuta has been introduced widely, and is now in Europe, Asia Minor, Africa, the Mascarene and Macaronesian Islands, India, Nepal, marginal East Asia, Australia, New Zealand, Polynesia, Brasil and Argentina.
Introduced to Australia, probably from North America or Europe. Occurs throughout much of Australia, mainly (but not exclusively) in coastal drainages in agricultural and urban areas where it is usually abundant.
This introduced species is abundant in many waterways in temperate Australia and is often referred to as Physella acuta or sometimes Haitia acuta.
Physa is easily confused with species of Glyptophysa (Planorbidae) which have similar-shaped, sinistral shells. Physa can be distinguished by its completely smooth shell (Glyptophysa often - but not always - has some periostracal ornament) and mottled mantle which can usually be readily seen through the semi-transparent shell (Glyptophysa has a uniformly dark-coloured mantle). The animal also has digitations (finger-like processes) along the mantle edge against the columella (smooth in Glyptophysa) and there is no false gill (pseudobranch) (present in Glyptophysa). The animal, if damaged when alive, does not produce coloured blood, whereas Glyptophysa has red- coloured blood.
Species of Isidorella should also be compared, but differ from Physa in the same characters given above for Glyptophysa.
Physa mexicana (Philippi in Küster, 1841) - also from North America - is widespread throughout the world as well and is indistinguishable from P. acuta in shell morphology however P. acuta differs in the elongate sarcobelum in the reproductive system which is a feature not seen in P. mexicana (Taylor, 2003) Because of the similarity of both species it is currently unknown if P. mexicana is present in Australia. Other species such as Physa gyrina (Say, 1821) could also possibly be undetected.
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