Larval descriptions of three galaxiid fishes endemic to south-western Australia: Galaxias occidentalis, Galaxiella munda and Galaxiella nigrostriata (Salmoniformes: Galaxiidae)

Abstract

The larval development of Galaxias occidentalis, Galaxiella munda and Galaxiella nigrostriata is described and illustrated with material collected from freshwater habitats in south-westem Australia. Galaxias occidentalis larvae are very elongate (52-54 myomeres), lightly pigmented and morphologically very similar to those of Galaxias vulgaris and Galaxias maculatus. Notochord flexion (9.3-13.1 mm), formation of all except the pelvic fins (6.1-21.9 mm) and transition (>26.6 mm) in larval G. occidentalis occur at similar sizes to larvae of the strictly freshwater G. vulgaris but at smaller sizes than in larvae of diadromous populations of G. maculatus. Larvae of Galaxiella munda and G. nigrostriata are elongate (3843 myomeres) and heavily pigmented and can be separated primarily by the considerably heavier pigmentation in the latter species. Notochord flexion (6.6-13.1 mm), formation of all except the pelvic fins (5.8-13.6 mm) and transition (>13.2 mm) in both species occur at smaller sizes than in Galaxias larvae. Galaxias larvae can be distinguished from those of many superficially similar clupeiform species by the combination of a dorsal fin directly above the anal fin, lack of a strongly striated hindgut, absence of a conspicuous gas bladder above the fore- and hindgut junction, and myomeres without cross-hatched muscle fibres. Galaxiella larvae are very different from Galaxias larvae and are unlikely to be confused with the larvae of any other sympatric species.