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]
| Otjikoto tilapia | |
|---|---|
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Cichliformes |
| Family: | Cichlidae |
| Genus: | Tilapia |
| Species: | T. guinasana
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| Binomial name | |
| Tilapia guinasana Trewavas, 1936
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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 edit
- ^ 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.
- ^ a b c Froese, Rainer; Pauly, Daniel (eds.) (2017). "Tilapia guinasana" in FishBase. April 2017 version.
- ^ 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.
- ^ a b SeriouslyFish: Tilapia guinasana. Retrieved 18 April 2017.
- ^ 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.
External links edit
- Photographs - Pinkish ("koi") individual, Olive (yellow) morph, Blue morph
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