''Beddomeia capensis'' is an aquatic operculate

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

, a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of very small

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastro ...

that has a

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

and an operculum, in the family

Hydrobiidae Hydrobiidae, commonly known as mud snails, is a large cosmopolitan family of very small freshwater and brackish water snails with an operculum; they are in the order Littorinimorpha. Distribution Hydrobiidae are found in much of the world, ...

. The species is classified as endangered and known to be

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to five streams within a relatively small area on the island state of

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. However, recent surveys have only been able to locate ''Beddomeia capensis'' in two small streams on

Table Cape Table Cape is a extinct volcano located near Wynyard, Tasmania, Wynyard on the North West Tasmania, North West of Tasmania, Australia, it is also the name of the locality which encompasses the geological feature. Table Cape is a more or less cir ...

, with the total length of inhabited stream less than .

Description

''B. capensis'' are small (1–7 mm) and difficult to identify to a species level in the field, being distinguished by a number of shell and anatomical characters. Their conical-shaped shells can be opaque to dark brown in colour. The shells are most often smooth, but may possess faint sculpturing. The shell is 2.21-2.71 mm long, 1.38-1.71 mm wide, with a protoconch of about 1.67 whorls. The species is not sexually dimorphic in length, width or shape, the principal characters used to separate species of

Beddomeia ''Beddomeia'' is a genus of very small freshwater snails that have a gill and an operculum, aquatic operculate gastropod mollusks in the family Tateidae. Species Species within the genus ''Beddomeia'' include: *'' Beddomeia acheronensis'' ...

are the male and female reproductive systems, which require microscopic dissection of specimens.

Population and habitat

''B. capensis'' is known from two small streams on Table Cape, where they are located on and under stones, leaves and wood where it feeds actively, grazing on

periphyton Periphyton is a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in most aquatic ecosystems. The related term Aufwuchs (German "surface growth" or "overgrowth") refers to the col ...

. Field observations indicate these snails have a preference for the underside and lower margins of rocks and stream debris.

Threats

Habitat disturbance

The principal identified threats to freshwater molluscs are agricultural clearing, forestry, mining and impoundment construction. As the species is confined to small order streams, it is consequently at a higher risk of being impacted by habitat degradation and modification due to agricultural land practises. The two remaining sites where the species is known to occur are on remnant native

riparian vegetation A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...

within cleared agricultural land. The loss of species at three previously recorded sites, is likely due to intensively modified stream channels resulting in loss of habitat and competition.

Interspecific competition

Owing to the restricted subpopulations of ''B. capensis'', they are considered vulnerable to interspecific competition and displacement from the exotic ''P. antipodarum'' (New Zealand mud snail), as they occur in areas already subjected to water quality degradation which is favoured by the exotic species.

Stochastic risk

The fragmented distribution of the subpopulations of ''B. capensis'' offer no opportunity for genetic exchange between subpopulations, thus exposing the species to a risk of extinction.

References

External links

* * {{Taxonbar, from=Q308065 Gastropods of Australia Hydrobiidae Beddomeia Endangered fauna of Australia Endemic fauna of Australia Gastropods described in 1993 Taxonomy articles created by Polbot