Lepidogalaxias Explained

Lepidogalaxias salamandroides is a species of small freshwater fish of Western Australia. It is the only member of the family Lepidogalaxiidae and genus Lepidogalaxias. Common names for this fish include salamanderfish and Shannon mudminnow. Although it is not a lungfish, it resembles lungfish in several respects, including its ability to survive dry seasons by burrowing into the sand. It is on the IUCN Red List as Endangered.

Morphology

Lepidogalaxias salamandroides is small with females measuring up to 7 cm in length. This species has a slender, elongate and cylindrical body. The colour is brownish-green on the upper parts, silver-speckled and blotched on the sides, very pale below, and the fin membranes are transparent. The reddish eyes are fixed, lack eye muscles and are covered by a secondary eyelid, but the fish is able to move its neck in any direction.[1] [2] [3]

Biology

The salamanderfish spawn in winter when water levels are highest.[4] Males have a uniquely modified anal fin used for internal fertilization. When not in use, it is folded strongly to the left or right and sheathed with a series of greatly enlarged scales.[5] [6] The females produce 100–400 eggs with a diameter of 1.1–1.3mm, which hatch into bottom-feeder larvae 5.5mm long. Larvae and juveniles grow rapidly to gain fat stores to survive the summer drought period. Individuals reach up to 5 years of age.

The salamanderfish is carnivorous, mainly feeding on aquatic insect larvae. When their habitat dries up they switch to atmospheric gas exchange via cutaneous respiration. The swim bladder on the other hand is not suitable for aerial respiration.[7]

Range and habitat

It has a limited distribution in acidic pools of water in heathland peat flats of southwest Australia, between the Blackwood and Kent Rivers. This range is across a distance of 180 kilometres, in an area of Northcliffe, they are common in this region.[2] Its habitat is semi-permanent water, small pools and streams that may be high in tannins and acidity (pH 3.0–6.5). They experience a range of water temperatures, daily changes of 16 to 32 degrees Celsius, in pools no deeper than 0.1 metres. The species rests on the bottom of the water using elongated pelvic and rounded caudal fins. These small and shallow pools may contain a population of around 150 individuals, are generally no larger than 600 square metres, and evaporate in the dry seasons. It is also unusual for its ability to survive desiccation by burrowing into sand, a process of aestivation, when the pools it lives in periodically evaporate.

Taxonomy

The species was first described in 1961 by Gerlof Fokko Mees.[8] This author identified the species as belonging to the Galaxiidae, but the relationship to those species was in doubt. Lepidogalaxias salamandroides was eventually placed among the Osmeriformes as a monotypic arrangement, Lepidogalaxias (Lepidogalaxiidae), in 1991.[9] This placement has been also challenged, and rightly so, as analyses of molecular data have shown that Lepidogalaxias is actually an old and isolated lineage basal to all other Euteleostei.[10] [11] The species is contained in the class Actinopterygii, ray-finned fish, and is sometimes given the taxonomic placements as Galaxiidae of the order Salmoniformes.

It is sometimes named as the mud minnow,[12] long-finned Galaxias,[12] scaled galaxias,[13] [12] or dwarf pencilfish,[12] however mud minnow usually refers to Galaxiella munda.[14] A further list of names refer to L. salamandroides as salamanderfish of Western Australia, West Australian salamanderfish, salamander fish, salamanderfish, and Shannon mudminnow.[2] [9] [12]

Notes and References

  1. Web site: Salamanderfish: Lepidogalaxias salamandroides Mees, 1961. McGrouther. M. . August 2005. Find a Fish. Australian Museum, 2006. 2008-10-26.
  2. Berra . Tim M. . Pusey, Bradley J. . October 1997. Threatened fishes of the world: Lepidogalaxias salamandroides Mees, 1961 (Lepidogalaxiidae). Environmental Biology of Fishes. 50. 2 . 201–202. 1573-5133. 10.1023/A:1007322606248. 1997EnvBF..50..201B . 21584756 .
  3. https://museum.wa.gov.au/sites/default/files/LEPIDOGALAXIAS%20SALAMANDROIDES%20MEES%20%C3%BB%20A%20REDESCRIPTION,%20WITH%20NATURAL%20HISTORY%20NOTES.pdf Lepidogalaxias salamandroides Mees - A Redescription, with Natural History Notes
  4. Web site: Bray. Dianne. Salamanderfish, Lepidogalaxias salamandroides. Fishes of Australia. 30 January 2020.
  5. Internal fertilization in Lepidogalaxias salamandroides Mees (Pisces: Lepidogalaxiidae) . 10.1111/j.1096-3642.1989.tb00554.x . 1989 . Pusey . B. J. . Stewart . T. . Zoological Journal of the Linnean Society . 97 . 69–79 .
  6. https://www.biodiversitylibrary.org/partpdf/374257 Lepidogalaxias salamandroides Mees — A Redescription, with Natural History Notes
  7. https://core.ac.uk/download/pdf/77136865.pdf Implications of climate change on the aestivating Salamanderfish, Lepidogalaxias salamandroides Mees and the Black-stripe Minnow, Galaxiella nigrostriata Shipway
  8. Mees, G. F. 1961. Description of a new fish of the family Galaxiidae from Western Australia. J. Roy. Soc. West. Aust. 44: 33–38.
  9. Web site: Lepidogalaxias_salamandroides. Berra. Tim M. . 1995. Version 01. The Tree of Life Web Project. 2008-10-26.
  10. Li, J., Xia, R., McDowall, R. M. (2010): Phylogenetic position of the enigmatic Lepidogalaxias salamandroides with comment on the orders of lower euteleostean fishes. Molecular Phylogenetics and Evolution vol. 57: 932–936
  11. BETANCUR-R, Ricardo; WILEY, Edward O.; ARRATIA, Gloria (2017): Phylogenetic classification of bony fishes. BMC Evolutionary Biology, vol. 17
  12. Web site: Common Names of Lepidogalaxias salamandroides. 2009-01-05. Common name summary. FishBase.
  13. Web site: Lepidogalaxias salamandroides Mees, 1961. Gerald R. Allen, Norbert J. Cross & Douglass F. Hoese. 27 Jun 2007. Australian Faunal Directory. Department of the Environment, Water, Heritage and the Arts. 2009-01-04.
  14. Book: Allen, G.R. . Midgley, S.H. . Allen, M. . Field Guide to the Freshwater Fish of Australia . Western Australian Museum . 2002 . Perth . 109 . 0-7307-5486-3 .