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Freshwater Mussels

Family: Hyriidae

Description:

Freshwater mussels spotted along the river bank. There are several species that have ID potential, but three species stand out: Velesunio ambiguus, Hyridella australis, and Alathyria pertexta pertexta. This is because they have wide distribution and are known to occur in this region, not forgetting size, appearance, and general description. Species such as H. australis and H. drapeta are classed as river mussels. They need permanent and flowing water to breed and survive so generally found in permanent flowing streams. However, more than 400 native described species occur in Australia, plus more than 100 that are yet to be formally described. They belong to class Bivalvia (two-shelled), order Unionoida, and represented in Australia by a single family, Hyriidae. All reproduce by means of a larval stage that is parasitic, usually on fish. Remnant shells had a nacre surface, aka mother of pearl. Size of the larger specimens seen had a width of approximately 10-12 cms, but I wasn't necessarily looking for the largest specimen at the time.

Habitat:

Australian freshwater molluscs are found in wide range of natural and man-made habitats, occupying rivers, streams, lakes, billabongs, ponds, dams, irrigation channels, and even isolated desert springs. This spotting was along the banks and small sandy beaches of the Severn River, Ballandean SEQ. It is a (usually) gently-flowing freshwater river, and originates further up in Sundown National Park, not far from this location. Having swum in this river, I can only suggest that water salinity levels are very low, and the abundance of mussels seen would also support this.

Notes:

Last photo (#6) is of Hydromys chrysogaster, commonly known as the water-rat, an Australian native, semi-aquatic rodent. Also commonly known by its preferred indigenous name "Rakali." https://www.projectnoah.org/spottings/21... I kept finding remnant "opened" mussel shells along the river bank and beaches. As it turns out, mussels and yabbies are amongst the rakali's favourite foods, and both are in plentiful supply in this river. Something else noticed at the time were the "alive and still intact" mussels found high up on the river banks. They definitely crawled there of their own accord, but I'm wondering why? (placing these links here so I don't forget them https://en.wikipedia.org/wiki/Freshwater... http://www.molluscs.at/bivalvia/index.ht... https://www.mdfrc.org.au/bugguide/displa... )

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Neil Ross
Spotted by
Neil Ross

Ballandean, Queensland, Australia

Spotted on Jul 22, 2017
Submitted on Jun 1, 2018

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