Hyridella (Hyridella) drapeta (Iredale, 1934)
This species differs from the other NSW species of Hyridella (except H. depressa) in having delicate beak sculpture. The shell is moderately elongate, oval, posteriorly evenly rounded and the posterior ridge is broad but weak and flattened while the dorsal margin is weakly winged. The beaks do not project above the dorsal margin and the ventral margin is straight to weakly concave. There is also a diagnostic sulcation between the anterior and posterior sections of the shell. The periostracum varies from steel grey to brown; it is never glossy and black as in Hyridella australis.
The shell reaches about 90 mm in length, and the height/length ratio is less than 50%.
Hyridella (Hyridella) drapeta (Iredale, 1934)
Common name: Freshwater mussel
Genus Hyridella Swainson, 1840
Original name: Hyridunio australis drapeta Iredale, 1934. Iredale, T. (1934). The freshwater mussels of Australia. Australian Zoologist 8: 57-78 pls 3-6.
Type locality: Brisbane River, Queensland.
Synonyms: Hyridunio australis orion Iredale, 1934; Hyridunio renutus Iredale, 1934; Hyridunio australis casus Iredale, 1943.
The last major taxonomic revision of Australian freshwater mussels was by McMichael and Hiscock (1958).
Based on the available molecular results, Walker et al. (2014) pointed out that a re-assessment of Australian hyriids is needed.
Shallow burrower in silty sand/mud in streams, billabongs and rivers. Suspension feeder. Larvae (glochidia) are brooded in the gills and, when released, become parasitic on fish gills before dropping to the sediment as young mussels. Releases glochidia from August to autumn. Parasitic on a wide range of freshwater fish including introduced mosquito fish (Gambusia holbrooki).
Coastal rivers and streams of southeast Queensland, New South Wales south to and including the Shoalhaven River but absent from the Nepean River. Present in Victoria in the Gellibrand River.
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