Otjikoto tilapia

Otjikoto tilapia
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Cichlidae
Genus: Tilapia
Species: T. guinasana
Binomial name
Tilapia guinasana
Trewavas, 1936

The Otjikoto tilapia (Tilapia guinasana) is a critically endangered species of cichlid fish endemic to Namibia where it was originally only found in Lake Guinas.[1][2] This very small sinkhole lake contains quite clear water that generally ranges between 18–25 °C (64–77 °F) depending on season,[3] and the Otjikoto tilapia has been seen down to depths of 67 m (220 ft).[1] Despite deriving its common name from the nearby Lake Otjikoto, it in not native to that lake, rather being an introduced species.[1] It is rare in the aquarium trade[4] and also kept in garden ponds in southern Africa.[3]

It is shoaling, but when breeding the pairs separate out, moving to the lake's vertical cliff edges where narrow ledges are used for breeding.[3] The eggs and young are aggressively guarded by the parents.[3] The Otjikoto tilapia mostly feeds on algae, including diatoms,[2] but it is an opportunistic omnivore and will also take invertebrates.[3]

The Otjikoto tilapia can reach a total length of up to 14 cm (5.5 in).[2] When breeding, the undeparts become black.[3] Otherwise it is very variable in coloration, occurring in five main morphs, which are not sex-limited: olive, olive striped, dark blue, blue striped and light blue. The last is itself quite variable and may show some white, yellow or blotches in black.[5] There are minor genetic differences between the morphs and assortative mating occurs, especially in the olive and dark blue (possibly showing the very early stages of separation into distinct species).[5] Some pale individuals have a highly mottled appearance, giving the species the nicknames African koi and Nguni fish.[3] The distinct polymorphism is not seen in the introduced population in Lake Otjikoto.[4] It is very closely related to the banded tilapia (T. sparrmanii) and the two species can interbreed.[1]

References

  1. 1 2 3 4 5 Bills, R. 2007. Tilapia guinasana. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. www.iucnredlist.org. Downloaded on 07 June 2013.
  2. 1 2 3 Froese, Rainer and Pauly, Daniel, eds. (2017). "Tilapia guinasana" in FishBase. April 2017 version.
  3. 1 2 3 4 5 6 7 van Jaarsveld, E. (December 2013). Otjikoto Tilapia. South African National Biodiversity Institure. Retrieved 18 April 2017.
  4. 1 2 SeriouslyFish: Tilapia guinasana. Retrieved 18 April 2017.
  5. 1 2 Nxomani; Ribbink; and Kirby (1999). DNA profiling of Tilapia guinasana, a species endemic to a single sinkhole, to determine the genetic divergence between color forms. Electrophoresis 20: 1781—1785.


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