A review of Galaxiella pusilla (Mack) (Teleostei: Galaxiidae) in south-eastern Australia with a description of a new species 

Abstract

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.

Short‐lived fishes: Annual and multivoltine strategies

“…Some Galaxiiformes from Australia are confirmed to have maximum lifespans shorter than a year (Humphries, 1986; Pen et al., 1993). Specifically, two small species Galaxiella nigristriata (Galaxiidae) and Galaxiella pusilla (Galaxiidae) (Humphries, 1986; Pen et al., 1993) live in rivers, creeks and seasonally desiccating pools in river alluvia (Coleman et al., 2015; Humphries, 1986). These species are able to survive habitat desiccation for an extended period of time in a wet mud or under logs and rocks (Coleman et al., 2015).…”

“…Specifically, two small species Galaxiella nigristriata (Galaxiidae) and Galaxiella pusilla (Galaxiidae) (Humphries, 1986; Pen et al., 1993) live in rivers, creeks and seasonally desiccating pools in river alluvia (Coleman et al., 2015; Humphries, 1986). These species are able to survive habitat desiccation for an extended period of time in a wet mud or under logs and rocks (Coleman et al., 2015). They reproduce repeatedly at several‐day intervals and die soon after maturity (Pen et al., 1993).…”

Forecasting climate‐driven habitat changes for Australian freshwater fishes

“…Levels of cryptic speciation within Australian freshwater fishes are high (e.g. Adams et al, 2013; Coleman et al, 2015; Raadik, 2014; Shelley et al, 2018), and taxonomic revisions may reclassify widespread species with broad geographic ranges and climatic niches into multiple species with more restricted geographic ranges and climatic niches. Thus, future taxonomic revisions could increase the proportion of species vulnerable to habitat loss and extinction.…”

Accounting for false positive detections in occupancy studies based on environmental DNA: A case study of a threatened freshwater fish (Galaxiella pusilla)

“…Galaxiella pusilla is a small (adults usually 30–40 mm in length) freshwater fish that typically occurs in shallow habitats (<1 m deep), with still or slow‐flowing water and dense cover of submerged and emergent aquatic vegetation such as shallow lakes, wetlands, swamps, billabongs, and small streams (Coleman, Hoffmann, & Raadik, 2015). A common feature of their natural habitats is dynamic wetting and drying cycles, where water levels often substantially contract and expand during dry periods and wet periods, respectively.…”