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Ecology, life history and conservation status of Westralunio carteri IREDALE 1934, an endemic freshwater mussel of South-western Australia

Klunzinger, Michael (2012) Ecology, life history and conservation status of Westralunio carteri IREDALE 1934, an endemic freshwater mussel of South-western Australia. PhD thesis, Murdoch University.

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Westralunio carteri, the only hyriid in south-western Australia, was nominated ‘Vulnerable’ (IUCN) in 1994. The aims of this study were to update the species’ range and determine factors limiting its distribution, quantify tolerance to threats, quantify reproduction, describe glochidia morphology, identify host fishes to support the species’ life cycle and estimate growth and age.

Extent of Occurrence (EOO) of W. carteri is currently 16,011.9 km2, a 63.3% decline from the historic EOO of 43,579.8 km2, suggesting that the species should be classified as ‘Endangered’ under IUCN guidelines. Multivariate analysis identified flow and drying as explaining most of the variation in the distribution data, while the difference between historic and current distribution was explained principally by salinity. Salinity tolerance experiments indicated LC50 values of 1.3 - 3.0 and LC95 of 3.2 - 4.3 g L-1. Artificial water removal suggested W. carteri is intolerant of drying for more than five days during summer without shade or moist sediments.

Westralunio carteri spawns during winter; embryos are brooded in the gills of females to become glochidia and released on mucus strings in September – December, when they attach to fins of fishes. Glochidia morphology (size and larval teeth) is distinctive in W. carteri, compared to other Australian hyriids.

Glochidia were found on fins of seven native and three alien fish species from 18 populations. Prevalence was 0.0 - 41.0% and 9.2 - 90.5% and intensity 1.0 - 6.0 and 2.3 - 7.1 in alien and native fishes, respectively. Four native and one alien fish species were confirmed as competent hosts in the laboratory. Time to metamorphosis was 21-27 days.

Growth rates were ~12.0 to <0.1 mm yr-1 in the smallest (<30 mm long) and largest (>75 mm long) sizes. Calcein validated growth rings as annuli and ages were 3 – 51 years at shell lengths of 12.6 - 82.5 mm, respectively, from five populations. Growth rates and ages-at-length were highly variable between populations.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Environmental Science
Supervisor(s): Lymbery, Alan, Morgan, David and Beatty, Stephen
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