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Hyridella (Protohyridella) glenelgensis Dennant,1898

Diagnostic features

This small species is distinctive in having a thick, rhomboid-shaped shell with a very strong hinge and strong shell sculpture of distinct rugose ridges and wrinkles. There is a posterior wing with a prominent ridge. The beaks are heavily sculptured with 'V’ shaped ridges and that sculpture extends onto the adult shell. Colour on outer surface olive to dark brown. Inside valves bluish, stained brown around the beaks. The shell reaches 40 mm in length and the height/length ration is 55-60%.

This species is separated from Hyridella (Hyridella) on the basis of its distinctive shell sculpture but is otherwise like Hyridella (Hyridella) in other shell features and general anatomy. McMichael & Hiscock (1958) noted that this species has prominent siphons of equal size, the anal (exhalant) siphon being brick red, branchial (inhalant) being darker with three rows of internal papillae internally. The marsupium occupies the middle third of the inner demibranch in females.

Classification

Hyridella (Protohyridella) glenelgensis Dennant,1898

Class Bivalvia

Subclass Heteroconchia

Superorder Palaeoheterodonta

Order Unionida

Superfamily Unionoidea

Family Hyriidae

Subfamily: Hyriinae

Genus Hyridella Swainson, 1840

Subgenus Protohyridella Cotton & Gabriel, 1932 (Type species: Unio glenelgensis Dennant, 1898).

Original name: Unio glenelgensis Dennant,1898. Dennant, J. (1898). Description of a new species of Unio from the River Glenelg. Proceedings of the Royal Society of Victoria 10: 112-113.

Type locality: Roseneath, Glenelg River, Victoria.

State of taxonomy

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.

Biology and ecology

Shallow burrower in silty sand/mud in streams and rivers. Suspension feeder. Larvae (glochidia) are brooded in the gills of females and, when released, become parasitic on fish gills before dropping to the sediment as young mussels.

Additional information on the biology and ecology of members of this family can be found in Fauna of Australia, vol. 5A, p. 296-298.

Distribution

Glenelg and Wannon Rivers of western Victoria. One old record in the Australian Museum from Port Fairy, Victoria collected in the late 1800s, presumably from the now degraded Moyne River.

Notes

This species is listed as critically endangered on the IUCN Red List. 

Further reading

Jones, H. A. & Byrne, M. (2014). Changes in the distributions of freshwater mussels (Unionoida: Hyriidae) in coastal southeastern Australia and implications for their conservation status. Aquatic Conservation: Marine and Freshwater Ecosystems 24: 203-217.

Iredale, T. (1934). The freshwater mussels of Australia. Australian Zoologist 8: 57-78 pls 3-6.

Iredale, T. (1943). A basic list of the fresh water Mollusca of Australia. Australian Zoologist 10: 188-230.

Lamprell, K. & Healy, J. (1998). Bivalves of Australia, volume 2. Leiden, Backhuys Publishers.

McMichael, D. F. & Hiscock, I. D. (1958). A monograph of the freshwater mussels (Mollusca: Pelecypoda) of the Australian region. Australian Journal of Marine and Freshwater Research 9: 372-508.

Playford, T. J. & Walker, K. F. (2008). Status of the endangered Glenelg River Mussel Hyridella glenelgensis (Unionoida: Hyriidae) in Australia. Aquatic Conservation: Marine and Freshwater Ecosystems 18: 679-691.

Smith, B. J. (1992). Non-marine Mollusca. Pp. i-xii, 1-408 in W. W. K. Houston. Zoological Catalogue of Australia, 8. Canberra, Australian Government Publishing Service.

Smith, B. J. & Kershaw, R. C. (1979). Field guide to the non-marine Molluscs of South-eastern Australia. Canberra, A.N.U. Press.

Walker, K. F. (1981). The distribution of freshwater mussels (Mollusca: Pelecypoda) in the Australian zoogeographic region. Pp. 1233-1249 in A. Keast. Ecological Biogeography of Australia. The Hague, Dr W. Junk.

Walker, K. F. (2004). A guide to the provisional identification of the freshwater mussels (Unionoida) of Australasia. Albury, Murray Darling Freshwater Research Centre.

Walker, K. F., Byrne, M., Hickey, C. W. & Roper, D. S. (2001). Freshwater Mussels (Hyriidae) of Australasia. Pp. 5-31 in G. Bauer & Wächtler, K. Ecology and Evolution of the Freshwater Mussels Unionoida. Ecological Studies. Berlin, Springer-Verlag.

Walker, K. F., Jones, H. A. & Klunzinger, M. W. (2014). Bivalves in a bottleneck: taxonomy, phylogeography and conservation of freshwater mussels (Bivalvia: Unionoida) in Australasia. Hydrobiologia 735: 61-79.