• Source: Physa

Physa is a genus of small, left-handed or sinistral, air-breathing freshwater snails, aquatic pulmonate gastropod molluscs in the subfamily Physinae of the family Physidae.
These snails eat algae, diatoms and detritus.




Anatomy


Members of the freshwater pulmonate family Physidae possess a complex of muscles that is unique amongst gastropods. This complex was given the name "physid musculature". The physid musculature has two main components, the physid muscle sensu stricto and the fan muscle. The physid musculature is responsible for a unique ability of physids to rapidly flick their shells from side to side — a reaction that frequently enables them to escape predation.




Shell description


These small snails, like all the species in the family Physidae, have shells that are sinistral, which means that when the shell is held with the spire pointing up and the aperture facing the viewer, then the aperture is on the left-hand side.
The shells of Physa species have a long and large aperture, a pointed spire, and no operculum. The shells are thin and corneous, and rather transparent.




Species


Species in the genus include:

Synonyms

Physa acuta Draparnaud, 1805, Physa heterostropha (Say, 1817), Physa integra (Haldeman, 1841) and Physa natricina Taylor, 1988 are synonyms of Physella acuta (Draparnaud, 1805)
Physa ancillaria (Say, 1825) – Pumpkin Physa: synonym of Physella ancillaria (Say, 1825) (original combination)
Physa carolinae Wethington, Wise & Dillon, 2009: synonym of Physella carolinae (Wethington, Wise & Dillon, 2009)
Physa concolor Haldeman, 1841: synonym of Physella gyrina (Say, 1821)
Physa columbiana (Hemphill, 1890) is a synonym for Physella columbiana (Hemphill, 1890)
Physa gyrina (Say, 1821) is a synonym for Physella gyrina (Say, 1821)
Physa hordacea (I. Lea, 1864): synonym of Physella hordacea (I. Lea, 1864)
Physa jennessi Dall, 1919: synonym of Beringophysa jennessi (Dall, 1919)
Physa lordi (Baird, 1863): synonym of Physella lordi (Baird, 1863)
Physa marmorata Guilding, 1828 – synonyms: Physa mosambiquensis Clessin, 1886 and Physa waterloti: synonym of Stenophysa marmorata (Guilding, 1828)
Physa natricina Taylor, 1988: synonym of Physella natricina (D. W. Taylor, 1988)
Physa nuttalli I. Lea, 1864: synonym of Physella gyrina (Say, 1821)
Physa propingua (Tryon, 1865): synonym of Physella propinqua (Tryon, 1865)
Physa sibirica Westerlund, 1876: synonym of Sibirenauta sibirica (Westerlund, 1876)




References



Janus, Horst, 1965. ‘’The young specialist looks at land and freshwater molluscs’’, Burke, London




External links



http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/list/species?taxongenus=301
Dillon R. T., Wethington A. R. & Lydeard C. (2011). "The evolution of reproductive isolation in a simultaneous hermaphrodite, the freshwater snail Physa". BMC Evolutionary Biology 11: 144. doi:10.1186/1471-2148-11-144.

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