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Velesunio wilsonii
	Velesunio wilsonii from the Ross River, Townsville, Queensland, Australia
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Unionida
Family:	Hyriidae
Genus:	Velesunio
Species:	V. wilsonii
Binomial name
	Velesunio wilsonii; (Lea, 1859)
Synonyms
	Unio (Alasmodon) stuarti Adams & Angas, 1864; Centralhyria wilsonii caurina Iredale, 1934.;

Velesunio wilsonii is a species of freshwater mussel endemic to Australia and comes from the Hyriidae family (phylum: Mollusca).^[1] Velesunio wilsonii mussels have a thick, dark shell that are sometimes flaky and mostly closed.^[1] Velesunio wilsonii have a fleshy foot that sometimes extends outside of the valves.^[1] The shell of the Velesunio wilsonii varies from oblong to a symmetrical circle.^[1] Velesunio wilsonii size ranges from 40 mm to 120 mm.^[1]

Biology and ecology

Reproduction in Velesunio wilsonii generally involves the male mussels releasing sperm that females take up to fertilize their eggs.^[2] Once fertilized, the embryos develop within the females’ gills.^[2] These develop into larvae (glochidia), which then attach to the gills or fins of native fish, acting parasitic.^[3] They remain attached to the fish by hooks until they have metamorphosed into juvenile mussels ^[2] with siphon structures that allow them to feed.^[4] Velesunio wilsonii siphon water into these structures and filter-feed, filtering out algae and nutrients.^[1] Once fully developed, Velesunio wilsonii live in the sediment of rivers and floodplains and remain relatively sedentary throughout their life.^[1] Due to their ability to tolerate changing environmental conditions, Velesunio wilsonii can live for a long period of time.^[5]

Dispersal of Velesunio wilsonii mussels in adult stages is limited and they remain mostly sedentary.^[5] However, it has been suggested that mussels from the Velesunio genus are dispersed when attached to the fish in their larvae stage.^[5] This may explain the large range of Velesunio wilsonii within Australia.^[5]

Distribution

Velesunio wilsonii mussels are distributed throughout several areas of Australia.^[5] Velesunio wilsonii can be found in the Northern Territory, Western Australia, Queensland, northeast of South Australia and northern New South Wales.^[6] There are no records of Velesunio wilsonii in Victoria or Tasmania.^[3]

Habitat

Velesunio wilsonii occurs in lowland floodplain ecosystems, including billabongs, temporary and episodic streams,^[4] irrigation canals and farm dams.^[1] Velesunio wilsonii live partially buried in fine sediments such as sand and mud.^[1] When buried and their shell is closed, Velesunio wilsonii can survive in drought conditions, high temperatures and low levels of oxygen,^[4] allowing them to inhabit a wide range of ecosystem types.^[1]

Evolution

Velesunio wilsonii come from one of two classes of molluscs that have successfully inhabited freshwater ecosystems.^[1] All other mollusc classes remain in marine ecosystems.^[1] Bivalve molluscs evolved in marine ecosystems before slowly moving into estuaries and inhabiting upstream freshwater habitats, evolving to tolerate lower salinity levels.^[1] Velesunio wilsonii is an example of this evolution.^[1]

Threats

Velesunio wilsonii mussels are threatened with changes to biotic and abiotic conditions of lowland river ecosystems.^[7] Changes to flow regimes through dam and weir construction may limit the ability of host fish to disperse, limiting the dispersal of Velesunio wilsonii larvae.^[7] Changes to flow regime may also affect the ecology of the host fish, causing host fish populations to decline.^[7] Increased erosion, sedimentation and pollutant runoff may also affect the survival of Velesunio wilsonii, affecting the water quality of floodplains.^[7]