Physella acuta, also known as European physa, tadpole snail, bladder snail, or acute bladder snail, is a species of small, sinistral, air-breathing freshwater snail of the family Physidae. It originates from North America and is established across all continents except Antarctica, mainly due to the aquarium trade.[3] It is considered "the world's most cosmopolitan freshwater gastropod".[4]
Taxonomic history
The name Physella means "little bladder", derived from the Greekphysa[5] and the diminutive suffix "-ella". The specific epithetacuta is Latin for "sharp".[6]
Physella acuta was first described in France as Physa acuta,[7] and later independently in Pennsylvania, USA, as Physa heterostropha. For a long time these were treated as separate species, alongside several others, until molecular and reproductive studies showed they represented a single species.[8]
Physella acuta was originally placed within the genus Physa and later reassigned to its current classification Physella. However, species- and genus-level memberships within the subfamily Physinae are still debated[9][10] and the taxonomy of P. acuta is still unsettled. Many recent studies still refer to the species as Physa acuta[11] or cite it as both Physa and Physella.[12][13] These taxonomic challenges may stem from vague descriptions in early works which could apply to multiple taxa[14] and from the generalist nature of many physids including P. acuta, which lead to morphological plasticity and rapid evolution.[15]
Description
Shell of Physella acuta
Snails in the family Physidae are distinguished by shells lacking an operculum, shaped as a high spiral, and having a sinistral direction, which means that if the shell is held with the aperture facing the observer and the spire pointing up, then the aperture is on the left-hand side.[16]
Specific to P. acuta is a thin shell with a pointed apex and four to five whorls. The aperture is ear-shaped, 3/4 of the shell's height in size, and has a white lip. Descriptions of the shell's colour range from "fawn" to "yellowish" and slightly transparent due to its thinness. The body of P. acuta is described as grey or "blackish" with a spotted mantle, often visible through the shell.[17][18]
Distribution
P. acuta was originally thought to be native to the Mediterranean region. However, reproductive isolation experiments[19] and molecular genetic studies[20] revealed it to be the same species as the North American Physella heterostropha and Physa integra.[21] Additional evidence of a North American origin includes numerous fossils of the species North America, comparative anatomy of its reproductive organs, and phylogenetic data. It is now widely accepted that P. acuta is native to North America, specifically the United States, and was introduced to Europe later.[21][22]
There is currently no consensus on P. acuta's native range within the United States, with studies suggesting both an Eastern and a Western origin. A third hypothesis suggests a single, historically isolated population that only recently resumed genetic exchange.[23] Similarly, the time and means of P. acuta's arrival in Europe is still unclear. Its first introduction to Europe is hypothesised to stem from eastern P. acuta populations through the cotton trade in the 18th century,[23] although earlier and even natural introductions are also possible.[24] Its initial spread throughout Europe was likely facilitated by man-made canals.[24][25] Today, P. acuta is widely dispersed across the globe, largely due to the aquarium trade.[26] It can be found on all continents except Antarctica.[27]
Regional highlights
North America
United States – native, although its specific native range is not yet clear.[17]
According to the U.S. Geological Survey (USGS), P. acuta can occupy a variety of freshwater habitats as well as habitats varying widely in water availability.[17] It has been reported in lakes, reservoirs, ponds, streams, ditches, among other water bodies.[40][41] The species is tolerant to many harsh environmental conditions including eutrophic and polluted environments.[42][43][44]
Feeding habits
These snails eat dead plant and animal matter and various other detritus. Because Physella acuta forages mainly on epiphytic vegetation and on the macrophytes, whereas other gastropods (Planorbis planorbis, Radix ovata) exploit the algal cover or phytobentos on the bottom, competition between Physella acuta and other gastropods appears to be minimal.[35]
Reproduction
P. acuta is a self-compatible hermaphrodite. In natural populations, P. acuta preferentially reproduces by outcrossing.[45] When individuals from such populations self-fertilize they show a high degree of inbreeding depression. However, in experimentally constrained lines (where mates were often unavailable), after about 20 generations of self-fertilization, most of the inbreeding depression was purged.[45]
Interspecific relationships
This species successfully co-exists with other alien gastropods: for example with Potamopyrgus antipodarum in many streams, lakes and ponds in both New Zealand and the United Kingdom; and with Lithoglyphus naticoides in the Danube River.[35] The presence of P. acuta may encourage proliferation of invasive non-native macrophytes such as Nuttall's waterweed (Elodea nuttallii). The bladder snail is a frequent prey of many snail-eating predators, such as
Physella acuta is often called a "pest snail" in freshwater fishkeeping. It usually spreads by laying its eggs on ornamental plants which are then bought and taken home. Physella acuta can reproduce quickly compared to other snails, in part to its ability to self-fertilise. It is generally non-harmful to the aquarium, but often found to be unsightly as well as adding to the aquarium's waste production. Others will, however, intentionally keep bladder snails, as their diet and ease of care can prove to make them a useful part of a tank's clean-up crew.
References
This article incorporates CC-BY-2.0 text (but not under GFDL) from reference.[35]
↑ Draparnaud J.-P.-R. 1805. Histoire naturelle des mollusques terrestres et fluviatiles de la France. Ouvrage posthume. Avec XIII planches. pp. [1-9], j-viij [= 1-8], 1-134, [Plates 1-13]. Paris, Montpellier. (Plassan, Renaud).
↑ Draparnaud, Jacques-Philippe-Raymond (1805). Histoire naturelle des mollusques terrestres et fluviatiles de la France (in French). ISBN9780274941360.{{cite book}}: ISBN / Date incompatibility (help)
↑ Vázquez A. A. & Perera S. (2010). "Endemic Freshwater molluscs of Cuba and their conservation status". Tropical Conservation Science3(2): 190–199. HTM, PDF.
1 2 (in Czech) Horsák M., Juřičková L., Beran L., Čejka T. & Dvořák L. (2010). "Komentovaný seznam měkkýšů zjištěných ve volné přírodě České a Slovenské republiky. [Annotated list of mollusc species recorded outdoors in the Czech and Slovak Republics]". Malacologica Bohemoslovaca, Suppl. 1: 1–37. PDF.
↑ Beran, L. (2002) Vodní měkkýši České Republiky – rozšíření a jeho změny, stanoviště, šíření, ohrožení a ochrana, červený seznam. Aquatic molluscs of the Czech Republic – distribution and its changes, habitats, dispersal, threat and protection, Red List. – Sborník přírodovědného klubu v Uherském Hradišti, Supplementum 10, 258 pp. (in Czech)
1 2 Noël E, Chemtob Y, Janicke T, Sarda V, Pélissié B, Jarne P, David P. Reduced mate availability leads to evolution of self-fertilization and purging of inbreeding depression in a hermaphrodite. Evolution. 2016 Mar;70(3):625-40. doi: 10.1111/evo.12886. Epub 2016 Mar 9. PMID 26899922
1 2 Paul, Pranesh; Das, Rajat; Nandy, Gargi; Aditya, Gautam (October 2022). "Preferring what others avoid: differences in the vulnerability of freshwater snails to the exotic and native predators". Hydrobiologia. 852 (5): 1385–1396. doi:10.1007/s10750-022-05062-w. ISSN1573-5117. S2CID253133418.
Naranjo-García E. & Appleton C. C. (2009). "The architecture of the physid musculature of Physa acuta Draparnaud, 1805 (Gastropoda: Physidae)". African Invertebrates50(1): 1-11. Abstract
External links
Physa acuta at AnimalBase taxonomy, short description, distribution, biology, status (threats), images
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