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Austropyrgus tumidus Clark, Miller & Ponder 2003

Diagnostic features

This species belongs to the Austropyrgus sparsus group, whose members are characterised by the following shell features: small to medium sized shells, conical, with convex to slightly convex whorls. Furthermore, in females, the coiled oviduct is of an inverted U-shape or with two or more bends, loops or twists.

Austropyrgus tumidus differs from other members of the group in the following combination of characters: shell small, broad, with squat spire and straight to weakly-convex spire outline and convex whorls, inner lip of aperture narrowly to distinctly separated from parietal wall; inner marginal teeth with 17–19 cusps; more than ½ of pericardium in pallial roof; about ½ of prostate gland in pallial roof; rectum separate from capsule gland.

This species is found in sympatry with two other species of Austropyrgus (A. pusillus and A. glenelgensis) throughout its currently recognized range. The shell of this species differs from A. pusillus in its much larger and broader shell, and from A. glenelgensis in its smaller, more truncated shell. It is also similar in shell shape to A. exiguous, but larger and broader.

Classification

Austropyrgus tumidus Clark, Miller & Ponder 2003

Class Gastropoda

Subclass Caenogastropoda

Order Littorinimorpha

Superfamily Truncatelloidea

Family Tateidae

Genus Austropyrgus Cotton, 1942

Original name: Austropyrgus tumidus 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: Spring at Post and Rail North Camp, 5.4 km east of Battersleys Camp, Lower Glenelg National Park, Victoria.

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 few small springs and streams flowing into the lower part of the Glenelg River, western Victoria.

Notes

Most members of Austropyrgus, including this species, are geographically isolated and have restricted 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.