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Fluvidona Iredale, 1937

Diagnostic features

Shell length 1.8-2.4 mm, spire moderately elongate to average length, with convex outline, aperture oval to almost circular, slightly disjunct. Teleoconch of about 2.6.3.8 rather flattened to convex whorls, last whorl and base evenly convex. Protoconch of about 1.2-1.3 whorls, sculptured with minute pits. Teleoconch sculptured with fine collabral growth lines only. Inner lip of aperture in contact with, or narrowly separated from, parietal wall; outer lip weakly thickened to thickened, typically with slight reflection, sometimes simple. Colour white to very pale yellow, translucent to opaque. Periostracum smooth, thin, transparent. Operculum rather thick, flat, reddish, with eccentric nucleus. Inner side with 1-5 pegs, occupying 3.30% of the opercular length.

In Fluvidona the stomach lacks a caecum and the oviduct joins the bursal duct dorsally. All species except one (F.orphana) lack a penial lobe. The radula has two pairs of basal cusps and small cusps on the cutting edges of the lateral and central teeth.

Classification

Class Gastropoda

Subclass Caenogastropoda

Order Littorinimorpha 

Superfamily Truncatelloidea

Family Tateidae

Genus Fluvidona Iredale, 1937

Type species: Hydrobia petterdi Smith, 1882

Original reference: Iredale, T. (1937). A basic list of the land Mollusca of Australia. Australian Zoologist 8, 287-333.

Type locality: Richmond River, New South Wales and Alert. (? =Albert) River, Queensland.

Biology and ecology

Found in small streams under loose or deeply embedded rocks, and under fallen palm fronds and amongst submerged leaves; also in soil in small, dry stream channel at one locality. Egg capsules have been found attached to sand grains. These are transparent, smooth, 0.4-0.5 mm in width, circular to oval in outline, lens-shaped (about 1/3 as high as wide), and contain one to two eggs.

Distribution

Fluvidona is restricted to north-eastern New South Wales and south-eastern Queensland.

Notes

Available evidence suggests that species of Fluvidona are highly restricted in their distributions. A number of undescribed species are known.

Further reading

Beesley, P. L., Ross, G. J. B. & Wells, A., Eds. (1998). Mollusca: The Southern Synthesis. Parts A & B. Melbourne, CSIRO Publishing.

Miller, A. C., Ponder, W. F. & Clark, S. A. (1999). Freshwater snails of the genera Fluvidona and Austropyrgus (Gastropoda, Hydrobiidae) from northern New South Wales and southern Queensland, Australia. Invertebrate Taxonomy 13: 461-493.

Ponder, W. F. (1994). Australian freshwater Mollusca: conservation priorities and indicator species. Memoirs of the Queensland Museum 36: 191-196.