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Ascorhis occidua Ponder and Clark, 1988

Diagnostic features

The shell is very variable in shape and sculpture; some are smooth, others have distinct spiral ridges. It can be mono-coloured (brown or yellowish) or spirally banded. The aperture is unthickened and simple. Shells commonly have large egg capsules attached, which are 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, with no white smear or pegs on the inner side.

Classification

Ascorhis occidua Ponder and Clark, 1988

Class Gastropoda

Order Littorinimorpha

Subclass Caenogastropoda

Superfamily Truncatelloidea

Family Tateidae

Genus Ascorhis Ponder and Clark, 1988

Original name: Ascorhis occidua Ponder & Clark, 1988. Ponder, W. F. and 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.

Type locality: Wanarup Inlet, north of Busselton, Western Australia.

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

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, 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.