Diagnostic features

This species belongs to the Austropyrgus petterdianus group, whose members are characterised by the following shell features: aperture slightly disjunct, with last whorl and base evenly convex; outer lip without reflection; shell colour yellow-brown and translucent.

A. petterdianus differs from other members of the group in the following combination of characters: shell small, with elongate spire and convex whorls; pallial vas deferens slightly undulating at prostate gland; penis unpigmented; ventral channel indistinct with moderate sized muscular vestibule.

This species is among the few species of the genus that exhibit sexual dimorphism in shell height, with females significantly taller and narrower than males. It is unusual that females are narrower than males; typically they are broader.

Austropyrgus petterdianus is occasionally found in sympatry with A. tebus, from which it can be distinguished by its small narrow shell and elongated spire.

Classification

Austropyrgus petterdianus (Brazier, 1875)

Class Gastropoda

Infraclass Caenogastropoda

Order Littorinida

Suborder Rissoidina

Superfamily Truncatelloidea

Family Tateidae

Genus Austropyrgus Cotton, 1942

Original name: Amnicola petterdiana Brazier, 1875. In Brazier, J. (1875). Descriptions of eight species of Australian and Tasmanian land and freshwater shells. Proceedings of the Linnean Society of New South Wales 1: 17–20.

Type locality: Scottsdale, Tasmania.

Biology and ecology

In streams on water weeds, hard substrata (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.

Distribution

This species is known from a number of small streams around Scottsdale, northeast Tasmania.

Notes

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

Further reading