Status of the endangered Glenelg River Mussel Hyridella glenelgensis (Unionoida: Hyrudae) in Australia

1. Hyridella glenelgensis is a small freshwater mussel that occurs in the Glenelg-Wannon river system in south-western Victoria and is listed as 'threatened' under the state Flora and Fauna Guarantee Act 1988. The species has rarely been reported since its discovery in 1898, and there are no records from the late 1920s until 1990, and again in 2000, when small numbers were found in the Crawford River, a Glenelg tributary. 2. This investigation established that a population still persists in the lower reaches of the Crawford. The mussels prefer sandy sediment in flowing reaches where there is instrearn woody debris and overhanging vegetation. In these areas, the main threats are land clearance and stock access to the channel and riparian areas. 3. The shell morphology of H. glenelgensis and specimens presumed to be H. narracanensis from Eight Mile Creek, south-eastern South Australia, is distinct. Similar distinctions are apparent for shells from historical museum collections. 4. Mitochondrial DNA analysis of very small samples of mussels from the Crawford River and Eight Mile Creek indicates little genetic divergence, suggesting that these could be ecophenotypic variants of one species, which by priority would be H. glenelgensis. Scanning electron microscopy of glochidia indicates morphology typical of the genus. 5. Future investigations could include genetic analyses to confirm the taxonomic identity of the populations described here, surveys to locate new populations and measures to protect known habitats. Copyright (c) 2007 John Wiley & Sons, Ltd.