{{Short description|Species of gastropod}} {{Speciesbox | image = ChenuIllustrationsConchyliologiques1842Plate1.jpg | image_caption = ''Physella gyrina'' figure 10 | status = G5 | status_system = TNC | status_ref = <ref name=":1">{{cite NatureServe |id=2.815075 |title=''Physella gyrina'' |access-date=16 March 2026}}</ref> | taxon = Physella gyrina | authority = (Say, 1821)<ref name=":2">Say, T. (1821). "Descriptions of univalve shells of the United States". ''Journal of the Academy of Natural Sciences of Philadelphia'' '''2'''(1): 149-179.</ref> | synonyms = ''Physa gyrina'' Say, 1821 }}
'''''Physella gyrina''''', common name the "tadpole physa", is a species of small, left-handed or sinistral, air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk in the family Physidae.
==Shell description== Snails in the family Physidae have shells that are sinistral, which means that if the shell is held with the spire pointing up, and the aperture is facing the observer, the aperture is on the left-hand side.
The shells of ''Physella'' species have a long and large aperture, a pointed spire, and no operculum. The shells are thin and corneous and rather transparent.
left|thumb|Drawing of the eggs of ''Physella gyrina'': upper image is the egg-mass showing position of eggs in envelope. Lower images is a single egg showing the position of an embryo.
When food resources are limited, ''Physella gyrina'' allocates more energy to reproduction than growth, helping the species survive under harsh environmental conditions.<ref name=":3">{{cite journal |last1=Rollo |first1=C. D. |last2=Hawryluk |first2=M. D. |year=1988 |title=Compensatory scope and resource allocation in two species of aquatic snails |journal=Ecology |volume=69 |issue=1 |pages=146–156 |doi=10.2307/1943169 }}</ref>
Genetic studies indicate that ''Physella gyrina'' shows population level genetic differences across its range, suggesting that it adapts rapidly to diverse freshwater environments.<ref name=":4">{{cite journal |last1=Stanford |first1=B. C. M. |last2=Lepitzki |first2=D. A. W. |last3=Taylor |first3=M. K. |last4=Rogers |first4=S. M. |year=2023 |title=Pooled whole genome sequencing of the endangered Banff Springs snail, Physella johnsoni, reveals genetic separation to P. gyrina and cryptic micro-geographical genetic structure |journal=Conservation Genetics |volume=24 |issue=6 |pages=783–791 |doi=10.1007/s10592-023-01538-x }}</ref>
==Distribution== This species is known to occur in: * the USA - indigenous * Great Britain - introduced * Ireland - introduced * Spain
==References==
{{Reflist}}
== External links == *[http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/species?id=2841 ''Physella gyrina''] at Animalbase taxonomy, short description, distribution, biology, status (threats), images
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Category:Physidae Category:Gastropods of North America Category:Fauna of the Great Lakes region Category:Gastropods described in 1821 Category:Taxa named by Thomas Say Category:Sinistral (left-coiled) gastropods