Little Galaxias, Galaxiella toourtkoourt Coleman & Raadik 2015


Other Names: Western Plains Galaxiella

A Little Galaxias, Galaxiella toourtkoourt, in Western Victoria, December 2016. Source: Greg Wallis / iNaturalist.org. License: CC BY Attribution-NonCommercial

Summary:

This is the smallest known galaxiid species in the world! The Little Galaxias is pale olive-brown, silvery-white below, with three black stripes along the sides (more distinct and complete in males), and a silvery-gold iris. Adult males have a broad bright orange-red stripe along the midside, while females usually have a narrow bright silver, gold, or mauve stripe (rarely pale orange). Adults also have two to three black blotches at the isthmus (fleshy area on the underside between gill chambers), occasionally with faint, discontinuous dots between the underside of the head and the pelvic-fin bases. Juveniles lack the distinct stripes of adults, and are mostly pale olive to beige above and silvery-white below.

The Little Galaxias is found only in coastal drainages in western Victoria and eastern South Australia.

Cite this page as:
Dianne J. Bray, Galaxiella toourtkoourt in Fishes of Australia, accessed 19 Nov 2017, http://fishesofaustralia.net.au/home/species/5101

Little Galaxias, Galaxiella toourtkoourt Coleman & Raadik 2015

More Info


Distribution

Endemic to south-eastern Australia from Barwon Downs in western Victoria to near the Coorong in south-eastern South Australia.
Inhabits swamps, wetlands, shallow lakes, billabongs, small creeks and artificial earthen drains at very low elevations (7–376 m). Habitats are mostly shallow (0.5–1.5 m), with still to low water velocities (or often backwaters in faster flowing conditions) and substantial shading (typically 10–60 % surface cover); occasionally found in inland slightly saline waters.

Features

Dorsal fin 5-8; Anal fin 7-10; Caudal fin 12-15; Pectoral fin 11-13; pelvic fin 5-6; Gill rakers 3-7 + 9-12 = 13-19; 7 laterosensory pores in the preopercular-supramaxillary series; Vertebrae 34-38.

Size

This is the smallest species in the genus Galaxiella, with females known to reach 42 mm TL (commonly 27–32 mm TL), and males to 34 mm TL (commonly 25–28 mm TL). The Little Galaxias is also the smallest species in the family Galaxiidae.

Biology

Spawns between late autumn to spring, and is an annual species that mostly dies soon after spawning.

Conservation

Currently considered threatened in South Australia (as Galaxiella pusilla) where it is also listed as ‘vulnerable’. 
In Victoria, G. toourtkoourt, (listed as ‘Galaxiella sp.’) is listed as threatened under the Victorian Fauna and Flora Guarantee Act 1988 (FFG Act). The species is considered Vulnerable in the Department of Environment, Land, Water and Planning (DELWP)’s Advisory List of Threatened Vertebrate Fauna in Victoria – 2013 (DSE 2013).

Habitat loss and fragmentation, and negative interactions with invasive fishes (particularly Gambusia holbrooki) are major threats to the long-term survival of this species.

Remarks

Galaxiella toourtkoourt differs from other species of Galaxiella in the following combination of characters: caudal fin rays usually 13 (12–15), anal fin rays usually 8 (7–10), pectoral fin rays usually 12 (8–13), usually 36 (34–38) vertebrae, 7 laterosensory pores in the preopercular-supramaxillary series. Adults very small (usually females 20.6–30.6 mm SL; males 16.7–24.0 mm SL); caudal peduncle short, usually 19.6–21.9 %SL (females 17.2–23.8 %SL; males 17.9–24.4 %SL); dorsal-fin origin more or less in line with anal-fin origin (particularly females) with horizontal distance between dorsal- and anal-fin origins usually 0.0–2.7 %SL (females -2.5–2.8; males -2.6–3.9). 

Similar Species

Differs from the similar Eastern Dwarf Galaxias, Galaxiella pusilla, in having the dorsal-fin origin more or less in line with that of the anal-fin origin, particularly females, (vs the origin of the dorsal fin distinctly posterior to that of anal fin in G. pusilla); caudal peduncle relatively short, usually 19.6–21.9% of SL, (vs caudal peduncle of moderate length, 21.3–23.8% of SL); ventral markings reduced, most commonly a small number of dark blotches in the vicinity of the isthmus (vs ventral markings distinct, most commonly a ‘v’-shaped dark mark originating in the isthmus and extending as two parallel dotted lines (sometimes discontinuous) to the pelvic fin bases. The species do not have overlapping distributions ranges.

Etymology

The specific name, pronounced “Too-urt Koo-urt” (or Tu-urt Ku-urt), is from the Australian indigenous language groups Tjapwurrung, Korn Kopan noot, and Peekwurrung, meaning ‘little fish in freshwater’.

Species Citation

Galaxiella toourtkoourt Coleman & Raadik, in Coleman, Hoffman & Raadik, 2015, Zootaxa 4021(2): 261, Figs. 3 to 4, 9, 10a, 11 & 12. Type locality: Surrey River, Wrights Swamp Road, Cobboboonee, Victoria,38° 8' 48"S 141° 24' 55"E.

Author

Dianne J. Bray

Little Galaxias, Galaxiella toourtkoourt Coleman & Raadik 2015

References


Beck, R.G. 1985. Field Observations of the Dwarf Galaxias Galaxiella pusilla (Mack) (Pisces: Galaxiidae) in the south-east of South Australia, Australia. South Australian Naturalist 60: 12–22.

Chilcott, S.J. & Humphries, P. 1996. Freshwater fish of northeast Tasmania with notes on the Dwarf Galaxias. Records of the Queen Victoria Museum and Art Gallery 103: 145-149.

Coleman, R.A. 2014. Conservation of the dwarf galaxias, Galaxiella pusilla (Mack 1936) (Teleostei: Galaxiidae), a threatened freshwater fish from south-eastern Australia. PhD Thesis, University of Melbourne, Parkville, 262 pp.

Coleman, R.A., Hoffman, A.A. & Raadik, T.A. 2015. A review of Galaxiella pusilla (Mack) (Teleostei: Galaxiidae) in south-eastern Australia with a description of a new species. Zootaxa 4021(2): 243-281. http://dx.doi.org/10.11646/zootaxa.4021.2.2 Abstract

Coleman, R.A., Pettigrove, V., Raadik, T.A., Hoffmann, A.A., Miller, A.D. & Carew, M.E. 2010. Microsatellite markers and mtDNA indicate two distinct groups in dwarf galaxias, Galaxiella pusilla (Mack) (Pisces: Galaxiidae), a threatened freshwater fish from south-eastern Australia. Conservation Genetics 11: 1911–1928. http://dx.doi.org/10.1007/s10592-010-0082-z (as Galaxiella pusilla ‘west region’)

Coleman, R.A., Weeks, A.R. & Hoffmann, A.A. 2013. Balancing genetic uniqueness and genetic variation in determining conservation and translocation strategies: a comprehensive case study of threatened dwarf galaxias, Galaxiella pusilla (Mack) (Pisces: Galaxiidae). Molecular Ecology 22: 1820–1835. doi: 10.1111/mec.12227 Abstract (as Galaxiella pusilla ‘west region’)

Department of Environment, Land, Water and Planning 2015 Action statement No.258. Flora and Fauna Guarantee Act 1988. Dwarf Galaxias, Galaxiella pusilla. Department of Environment, Land, Water and Planning (DELWP) Victoria. 16 pp. PDF

Hammer, M.P., M. Adams & R. Foster. 2012. Update to the catalogue of South Australian freshwater fishes (Petromyzontida & Actinopterygii). Zootaxa 3593: 59-74. (as Galaxiella pusilla)

Hammer, M., Wedderburn, S. & van Weenen, J. 2009. Action Plan for South Australian Freshwater Fishes. Native Fish Australia (SA), Adelaide, and Department of Environment and Heritage, Adelaide, 206 pp. (as Galaxiella pusilla)

Unmack, P.J., Bagley, J.C., Adams, M., Hammer, M.P. & Johnson, J.B. 2012. Molecular phylogeny and phylogeography of the Australian freshwater fish genus Galaxiella, with an emphasis on dwarf galaxias (G. pusilla). PLoS ONE 7: e38433. Open Access http://dx.doi.org/10.1371/journal.pone.0038433 (as Galaxiella pusilla ‘west region’)

Quick Facts


Conservation:Listed in SA & VIC

Depth:0.5–1.5 m

Habitat:Freshwater streams, wetlands

Max Size:30.6 mm SL; 42 mm TL

Native:Endemic

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