Velesunio wilsonii

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.

Distribution map of Velesunio wilsonii in Australia.

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]

Velesunio wilsonii shell

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]

References

1. Gooderham, John; Tsyrlin, Edward (2002). The Waterbug book: A Guide to the Freshwater Macroinvertebrates of Temperate Australia. Collingwood, Victoria: CSIRO Publishing. ISBN 0-643-09971-9.
2. Walker, K. F. (2016-07-18). "Reproductive phenology of river and lake populations of freshwater mussels (Unionida: Hyriidae) in the River Murray". Molluscan Research. 37 (1): 31–44. doi:10.1080/13235818.2016.1206166. ISSN 1323-5818. S2CID 89516859.
3. "Australian Freshwater Molluscs". keys.lucidcentral.org. Retrieved 2022-06-13.
4. Bauer, G; Wächtler, K (2001). Ecology and Evolution of the Freshwater Mussels Unionoida. Berlin: Springer. ISBN 978-3-642-63140-5. OCLC 44266465.
5. Hughes, Jane; Baker, Andrew M.; Bartlett, Christopher; Bunn, Stuart; Goudkamp, Katrina; Somerville, Jemma (2004-10-14). "Past and present patterns of connectivity among populations of four cryptic species of freshwater mussels Velesunio spp. (Hyriidae) in central Australia: CONNECTIVITY AMONG FRESHWATER MUSSELS". Molecular Ecology. 13 (10): 3197–3212. doi:10.1111/j.1365-294X.2004.02305.x. PMID 15367132. S2CID 20884876.
6. W. F. Ponder, A. Hallan, M. Shea, S. A. Clark (2016). Australian Freshwater Molluscs. Australian Museum. Accessed June 2018.
7. Walker, Keith F.; Jones, Hugh A.; Klunzinger, Michael W. (2013). "Bivalves in a bottleneck: taxonomy, phylogeography and conservation of freshwater mussels (Bivalvia: Unionoida) in Australasia". Hydrobiologia. 735 (1): 61–79. doi:10.1007/s10750-013-1522-9. hdl:10072/416124. ISSN 0018-8158. S2CID 254546281 – via ProQuest Central.