Physella acuta

Physella acuta is a species of small, sinistral, air-breathing freshwater snail of the family Physidae. Common names include European physa, tadpole snail, bladder snail, and acute bladder snail.

Physella acuta
A live individual of Physella acuta
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Superorder:	Hygrophila
Family:	Physidae
Genus:	Physella
Species:	P. acuta
Binomial name
Physella acuta (Draparnaud, 1805)[1]
Synonyms
Physa acuta Draparnaud, 1805 Physella heterostropha (Say, 1817)[2] Physella integra (Haldeman, 1841)[2] Physa globosa Haldeman, 1841 Haitia acuta

Taxonomic history

The name Physella means "little bladder", derived from the Greek physa,^[3] and the diminutive suffix "-ella". This is in reference to the genus Physa, which P. acuta has, at times, been placed in. Acuta is a Latin word meaning sharp.^[4]

Historically, Physella acuta was thought to be indigenous to the Mediterranean region.^[5][6] However, recent genetic studies has revealed it to be the same species as the North American Physella heterostropha.^[7] It is now widely accepted that P. acuta is native to North America and was introduced to Europe later.^[8]

Shell description

Shell of Physella acuta

Snails in the family Physidae have shells that are sinistral, 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.

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.

Distribution

Physella acuta is widely dispersed throughout the globe, largely due to the aquarium trade.^[9] Today, it can be found on all continents besides Antarctica.^[8]

Regional highlights

North America

• United States – native, although its specific native range is not yet clear.^[8]

• Cuba – native, the most common freshwater snail alongside Tarebia granifera.^[10]

South America

• Chile – invasive^[11]
• Brazil - invasive, first recorded in the northeastern state of Sergipe in 2019^[12]

Europe

• Czech Republic^[13] – not evaluated (NE)^[14]
• Slovakia^[13]
• Germany^[15]
• Netherlands^[16]
• Belarus – in the Neman River basin since 2007^[7]
• Pripyat River – since 1983^[7]
• United Kingdom – invasive, underwent naturalisation. Observed on several great rivers, streams, and tributaries within England, Wales, Scotland, and Northern Ireland including the River Severn and the River Thames.^[17] Its ecological impact was assessed by the United Kingdom Technical Advisory Group (UKTAG) as "Unknown".^[18]

Asia

• India^[19]
• Uzbekistan^[20]
• Kazakhstan^[20]

Oceania

• New Zealand – invasive, widespread and common.^[21]

Ecology

Habitat

This species lives in freshwater rivers, streams, lakes, ponds, and swamps.^[22]

Physella acuta is frequently found in anthropogenic reservoirs, occurring in warm water discharges from power stations and in some rivers, but very rarely and not numerously in clay pit ponds. It can survive well under temporary harsh conditions (extreme temperature and water pollution), as long as they are short-lived.^[7]

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.^[7]

Reproduction

P. acuta is a self-compatible hermaphrodite. In natural populations, P. acuta preferentially reproduces by outcrossing.^[23] 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.^[23]

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.^[7] 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

• Anomalochromis
• Badis badis
• Carinotetraodon travancoricus
• Puntius titteya
• Ambastaia sidthimunki
• Chromobotia macracanthus
• Clea helena^[24][25][26]
• Sternotherus carinatus
• Glossiphonia weberi^[24][27]

Aquarium trade

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.