Friday, September 25, 2015

[Ichthyology • 2015] Galaxiella toourtkoourt | Little Galaxias • A Review of Galaxiella pusilla (Mack) (Teleostei: Galaxiidae) in south-eastern Australia with A Description of A New Species

FIGURE 10. a) Galaxiella toourtkoourt male (upper) and female (lower) from Narrow Neck Drain, Hatherleigh, South Australia (Photo by M. Hammer),
b) Galaxiella pusilla s.s. male (lower) and female (upper) from Tuerong Creek, Moorooduc, Victoria (Photo by R. Kuiter).


The dwarf galaxias, Galaxiella pusilla (Mack), is a small, threatened freshwater fish from coastal south-eastern Australia. Recent genetic studies, using multiple nuclear and mitochondrial DNA markers, found substantial differences between populations in western Victoria and south Australia (‘west region’) compared to eastern Victoria, Flinders Island, and Tasmania (‘east region’) that suggest the presence of a cryptic species. Morphological measurements and meristic counts from multiple populations within each region were undertaken to investigate potential differences between regions. Several characters, found to discriminate between individuals in the regions and to be diagnostic for two taxa, were used to describe a new species, Galaxiella toourtkoourt, for the west region. This is only the second species in the Galaxiidae to exhibit sexual dimorphism. The original description of Galaxiella pusilla, based on five specimens, is revised following examination of a large number of individuals. Both species are considered nationally threatened and are categorised as ‘endangered’; the revised distribution of G. pusilla s.s. is reduced by approximately 60%. A number of inconsistencies in the most recent revision of the genus Galaxiella are also corrected.

Keywords: Pisces, taxonomic revision, dwarf galaxias, sexual dimorphism, threatened species, freshwater fish, cryptic species

Galaxiella toourtkoourt Coleman & Raadik, new species 
Little Galaxias

Etymology. Pronounced “Too-urt Koo-urt” (or Tu-urt Ku-urt), from the Australian indigenous language groups Tjapwurrung, Korn Kopan noot, and Peekwurrung, meaning ‘little fish in freshwater’. Recommended standard name as ‘Little galaxias’ based on it being the smallest species in the Galaxiidae (e.g. McDowall &Waters 2004) and consistency with ‘little’ in the indigenous language meaning. 

Distribution. Known from coastal south-eastern mainland Australia, from the upper Barwon River system near Barwon Downs, Victoria, west to the Cortina Lakes, near the Coorong, South Australia (Fig. 11). Its current known range does not overlap that of its sister species Galaxiella pusilla s.s. 

Rhys A. Coleman, Ary A. Hoffmann and Tarmo A. Raadik. 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.  DOI: 10.11646/zootaxa.4021.2.2