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Ascorhis tasmanica (von Martens, 1858)

Diagnostic features

The shell is very variable in shape and sculpture, some being smooth, others having distinct spiral ridges. The shell can be monocoloured (brown or yellowish) or spirally banded. The aperture is unthickened and simple. Shells often have the large egg capsules attached, these being coated with white sand grains. Living females are also distinctive in having a lateral pouch on either side of the snout. The operculum is simple, having no white smear or pegs on the inner side.

Classification

Ascorhis tasmanica (von Martens, 1858)

Class Gastropoda

Subclass Caenogastropoda

Order Littorinimorpha

Superfamily Truncatelloidea

Family Tateidae

Genus Ascorhis Ponder and Clark, 1988

Original name: Hydrobia tasmanica von Martens, 1858. Martens, E.C. von (1858). Ueber einige Brakwasserbe wohner aus den Umbebungen Venedigs Archiv für Naturgeschichte 24: 152 - 208.

Type locality: Tasmania (probably near Launceston).

Synonyms: Bythnia victoriae Tenison Woods, 1878; Hydrobia turbinata Petterd, 1889; Assiminea pagodella Hedley, 1902; Rissoa procincta Hedley, 1908; Potamopyrgus ruppiae Hedley, 1912; Webbinella bassensis Parr, 1945.

Biology and ecology

This tiny species lives on aquatic vegetation in the upper parts of estuaries and in coastal lagoons and is often abundant. It feeds by scraping bacteria and microalgae. The solitary hemispherical, sand-encrusted capsules contain a single egg, and are laided on virtually all substrates including being frequently attached to the shell of Ascorhis and other molluscs that co-occur with it. Development is direct.

Additional information on the biology and ecology of members of this family can be found in Fauna of Australia, vol. 5B, p. 752-755.

Distribution

From mid-Queensland through south-eastern Australia and into South Australia and Tasmania.

Notes

This species was long known as Hydrobia buccinoides but this name was changed to Ascorhis victoriae by Ponder and Clark (1988). However, the currently used name was later found to be an earlier name for this species (Ponder, 1997).

A closely related species (A. occidua Ponder and Clark, 1988) is found in south Western Australia.

Further reading

Beesley, P. L., Ross, G. J. B. & Wells, A., Eds. (1998). Mollusca: The Southern Synthesis. Parts A & B. Melbourne, CSIRO Publishing.

Ponder, W. F., Clark, S. A. & Dallwitz, M. J. (2000). Freshwater and estuarine molluscs: an interactive, illustrated key for New South Wales. Melbourne, CSIRO Publishing.

Ponder, W. F. & Clark, G. A. (1988). A morphological and electrophoretic examination of Hydrobia buccinoides, a variable brackish-water gastropod from temperate Australia (Mollusca: Hydrobiidae). Australian Journal of Zoology 36: 661-689.

Ponder, W. F. (1997). Nomenclatural rectifications in Australian Hydrobiidae. Molluscan Research 18: 67-68.

Ponder, W. F., Clark, S. A. & Dallwitz, M. J. (2000). Freshwater and estuarine molluscs: an interactive, illustrated key for New South Wales. Melbourne, CSIRO Publishing.

Robinson, K. & Gibbs, P. (1982). A field guide to the common shelled molluscs of New South Wales estuaries. Sydney, Coast and Wetlands Society (as Hydrobia buccinoides).

Smith, B. J. & Kershaw, R. C. (1979). Field guide to the non-marine Molluscs of South-eastern Australia. Canberra, A.N.U. Press (as Hydrobia buccinoides).

Smith, B. J. & Kershaw, R. C. (1981). Tasmanian Land and Freshwater Molluscs. Hobart, University of Tasmania (as Hydrobia buccinoides).