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Otjikoto tilapia

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Otjikoto tilapia
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cichliformes
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 underparts 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

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  1. ^ a b c d e Bills, R. (2007). "Tilapia guinasana". IUCN Red List of Threatened Species. 2007: e.T63354A12662434. doi:10.2305/IUCN.UK.2007.RLTS.T63354A12662434.en. Retrieved 14 November 2021.
  2. ^ a b c Froese, Rainer; Pauly, Daniel (eds.). "Tilapia guinasana". FishBase. April 2017 version.
  3. ^ a b c d e f g van Jaarsveld, E. (December 2013). Otjikoto Tilapia. Archived 2017-05-17 at the Wayback Machine South African National Biodiversity Institute. Retrieved 18 April 2017.
  4. ^ a b SeriouslyFish: Tilapia guinasana. Retrieved 18 April 2017.
  5. ^ a b 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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