Ascorhis occidua Ponder & 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 the large egg capsules attached, 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 & Clark, 1988

Class Gastropoda

Infraclass Caenogastropoda

Order Littorinida

Suborder Rissoidina

Superfamily Truncatelloidea

Family Tateidae

Genus Ascorhis Ponder and Clark, 1988

Original name: Ascorhis occidua Ponder & Clark, 1988. In 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.

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

Biology and ecology

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

Distribution

Southern part of 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.