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Austropyrgus nanoacuminatus Clark, Miller & Ponder 2003

Diagnostic features

This species belongs to the Austropyrgus petterdianus group, whose members are characterised by the following shell features: the shell aperture slightly disjunct, with last whorl and base evenly convex. The outer lip is without reflection, and the colour of shell is yellow-brown and translucent. A. nanoacuminatus differs from other members of the group in the following combination of characters: shell small, with elongated spire and straight to weakly convex spire outline; ctenidium with short efferent branchial blood vessel separating it from pericardium; prostate gland about 2/3 in pallial roof; pallial vas deferens strongly undulating at prostate gland; penis pigmented distally and medially; oviduct with one bend distal to seminal receptacle.

This species can be found in sympatry with three other species of Austropyrgus (A. lochi, A. conicus and A. smithii) throughout its currently recognized range and from which it can be distinguished by its small size, narrow elongate spire and slightly rounded whorls.

Classification

Austropyrgus nanoacuminatus Clark, Miller & Ponder 2003

Class Gastropoda

Subclass Caenogastropoda

Order Littorinimorpha

Superfamily Truncatelloidea

Family Tateidae

Genus Austropyrgus Cotton, 1942

Original name: Austropyrgus nanoacuminatus Clark, Miller & Ponder 2003. Clark, S. A., Miller, A. C. and Ponder, W. F. (2003). Revision of the snail genus Austropyrgus (Gastropoda: Hydrobiidae): A morphostatic radiation of freshwater gastropods in southeastern Australia.  Records of the Australian Museum Supplement 28: 1–109.

Type locality: Thirteen Mile Creek at Heazlewood Road, Mt Cleveland, Tasmania.

Biology and ecology

In streams on water weeds, hard substrate (rocks etc.) and crawling on litter and sediment. Can be locally abundant. Assumed to feed by scraping bacteria and microalgae. Lay solitary capsules containing a single egg. Direct development.

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

This species is known from a number of small streams, all of which are tributaries of the Arthur River, north-western Tasmania.

Notes

Although most species of Austropyrgus are geographically isolated and have restricted ranges, a few - such as A. nanoacuminatus - have wider ranges.

Further reading

Clark, S. A., Miller, A. C. & Ponder, W. F. (2003). Revision of the snail genus Austropyrgus (Gastropoda: Hydrobiidae): a morphostatic radiation of freshwater gastropods in southeastern Australia. Records of the Australian Museum 28: 1–109.