Order

Osmeriformes

  Class

Actinopterygii

No. in FishBase

Genera : 7 | Species : 53 Eschmeyer's Catalog of Fishes

  Environment

Fresh : Yes | Brackish : Yes | Marine : Yes

  Division

Peripheral/diadromous

  Aquarium

none

  First Fossil Record

     

  Remark

Galaxiids occur in Australia, New Zealand, New Caledonia, southernmost Africa, and southern South America. Freshwater; diadromous. Caudal fin 12-14 branched rays. No scales. Lateral line present. Abdomen without horny keel. No teeth on maxillary, vomerine, palatine, and basibranchial. Paired gonads. Without cucumber odor. In Subfamily Lovettinae vertebrae 52-58, maximum length about 7.7 cm; Subfamily Aplochitoninae vertebrae 64-74, maximum length 38 cm; and, Subfamily Galaxiinae vertebrae 37-66. Freshwater galaxiids = ISSCAAP 13; diadromous galaxiids = ISSCAAP 25. CLOFFSCA The galaxiids are freshwater fishes, some of which are diadromous, that occur in cool temperate waters of the Southern Hemisphere in Australia, Lord Howe Island, New Zealand, the Chatham Islands, Auckland and Campbell Islands, New Caledonia, southern South America, the Falkland Islands/Malvinas, and the southern tip of South Africa (Berra, 2001). There are seven genera (Aplochiton, Brachygalaxias, Galaxias [including Nesogalaxias from New Caledonia], Galaxiella, Lovettia, Neochanna, and Paragalaxias) and about 51 species. Five new species of Galaxias were described in the last few years when it was discovered that G. vulgaris from the South Island of New Zealand was actually a species complex (Wallis et al., 2000). Galaxiids are elongate, scaleless fishes and all lack an adipose fin except Aplochiton and Lovettia. Some species are rather stocky and tubular. Most species have seven pelvic and 16 caudal fin rays (McDowall, 1990), however there is wide variation of other elements of the caudal skeleton within and among species (McDowall, 1999). A lateral line is present. Some species may have an accessory lateral line composed of small, widely spaced neuromasts along the dorsolateral trunk from the occiput to the dorsal fin (McDowall, 1997). This accessory lateral line may function in sensing food or predators at the water's surface. The dorsal fin is situated posteriorly and more or less above the anal fin. Nelson (1994) listed three subfamilies of the Galaxiidae: Lovettiinae, Aplochitoninae, and Galaxiinae. The Lovettiinae is found only in Tasmania. The subfamily Aplochitoninae (previously considered a separate family) is composed of two species of Aplochiton from southern South America (McDowall 1971a). The dorsal fin of Aplochiton is anteriorly positioned over the pelvic fins. An adipose fin is present, and the caudal fin is forked. Aplochiton is probably amphidromous with the larvae being carried to sea after hatching in freshwater streams. McDowall (1984b) reported a post-larval Aplochiton taken at sea in southern Chile. The Galaxiinae includes five genera and about 48 species. This subfamily is most diverse in Australia, especially Tasmania, and in New Zealand. However, representatives also occur in South America, and one species inhabits Cape coastal streams at the southern tip of South Africa (Berra, 2001). No members of the family or subfamily occur in the Northern Hemisphere in spite of Day's description of G. indicus, which McDowall (1973b) regarded as a nomen dubium. Galaxias maculatus has one of the most widely disjunct distributions of any freshwater fish (Berra et al., 1996). Galaxias maculatus occurs in eastern and western Australia, Tasmania, Lord Howe Island, New Zealand, Chatham Island, southern Chile, Argentina, and the Falkland Islands/Malvinas (McDowall, 1970, Berra 2001). Two hypotheses have been advanced to explain this disjunct distribution: dispersal (movement through the sea) and vicariance (continental drift). A summary of this debate involving McDowall (1970), Rosen (1974, 1978) and others is given by Berra et al. (1996) who used allozyme electrophoresis of muscle extracts of G. maculatus from eastern and western Australia, New Zealand, and Chile to test the hypothesis that populations from the western Pacific and the eastern Pacific do not differ genetically. They found only minor differentiation in allele frequency at some loci and no fixation of alternative alleles. The populations appeared to be part of the same gene pool indicating that gene flow via dispersal through the sea occurs today. Only a small amount of gene flow is necessary to prevent accumulation of genetic differences by random drift. The marine larval stage of G. maculatus has a six-month period to traverse the distance between the southern continents (McDowall et al., 1994) and could provide enough gene flow to deter fixation for alternative alleles. A study of mitochondrial DNA sequence divergence by Waters and Burridge (1999) also supported the dispersal argument, but reported greater population differentiation than detected by Berra et al. (1996) with allozymes. Other South American galaxiids include two additional species of Galaxias and the small, colorful Brachygalaxias bullocki (McDowall, 1971b). Galaxias platei occurs in Chile, Argentina, and the Falkland Islands/Malvinas, and the very rare, if not extinct, G. globiceps is known from only a few specimens taken near Puerto Montt, Chile (Berra and Ruiz, 1994, Berra and Barbour, 1998). Brachygalaxias bullocki resembles Galaxiella of Australia, but whether this similarity is due to convergence or phylogeny is not clear. Waters (1996), Waters and Cambray (1997), and Waters et al. (2000) provided mtDNA data useful for phylogenetic analysis of galaxiids.

  Etymology

Greek, galaxías, -ou = a specie of fish ( Ref. 45335).

  Reproductive guild

nonguarders

  Typical activity level

active

  Main Ref

Nelson, J.S. 1994

  Coordinator

Nelson, J.S. 1994

  Deep Fin Classification

Osteichthyes | Actinopterygii | Actinopteri | Neopterygii | Teleostei | Osteoglossocephalai | Clupeocephala | Euteleosteomorpha | Protacanthopterygii | Galaxiiformes | Galaxiidae