The Otjikoto tilapia (''Tilapia guinasana'') is a critically endangered species of

cichlid Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses ( Labridae), in the order Perciformes, but molecular studies have contradicted this ...

fish

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

where it was originally only found in

Lake Guinas Lake Guinas is the larger of only two permanent natural lakes in Namibia. It is a ''sinkhole lake'', created by a collapsing karst cave, located thirty-eight kilometres west of Tsumeb, near the D3043 road. Lake Guinas is home to '' Tilapia guinasa ...

. This very small sinkhole lake contains quite clear water that generally ranges between depending on season,van Jaarsveld, E. (December 2013)
Otjikoto Tilapia.
South African National Biodiversity Institute. Retrieved 18 April 2017. and the Otjikoto tilapia has been seen down to depths of . Despite deriving its common name from the nearby Lake Otjikoto, it in not native to that lake, rather being an introduced species. It is rare in the

aquarium An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...

tradeSeriouslyFish
Tilapia guinasana.
Retrieved 18 April 2017. and also kept in

garden pond A garden pond is a water feature constructed in a garden or designed landscape, normally for aesthetic purposes, to provide wildlife habitat, or for swimming. Habitat Garden ponds can be excellent wildlife habitats, and can make a contribution ...

s in southern Africa. It is

shoaling In biology, any group of fish that stay together for social reasons are shoaling, and if the group is swimming in the same direction in a coordinated manner, they are schooling. In common usage, the terms are sometimes used rather loosely. Ab ...

, but when breeding the pairs separate out, moving to the lake's vertical cliff edges where narrow ledges are used for breeding. The eggs and young are aggressively guarded by the parents. The Otjikoto tilapia mostly feeds on

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

, including

diatom A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...

s, but it is an opportunistic

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...

and will also take invertebrates. The Otjikoto tilapia can reach a

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

of up to . When breeding, the underparts become black. Otherwise it is very variable in coloration, occurring in five main morphs, which are not

sex-limited Sex-limited genes are genes that are present in both sexes of sexually reproducing species but are expressed in only one sex and have no penetrance, or are simply 'turned off' in the other. In other words, sex-limited genes cause the two sexes to ...

: 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.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. There are minor genetic differences between the morphs and

assortative mating Assortative mating (also referred to as positive assortative mating or homogamy) is a mating pattern and a form of sexual selection in which individuals with similar phenotypes or genotypes mate with one another more frequently than would be exp ...

occurs, especially in the olive and dark blue (possibly showing the very early stages of separation into distinct species). Some pale individuals have a highly mottled appearance, giving the species the nicknames African

koi or more specifically , are colored varieties of the Amur carp ('' Cyprinus rubrofuscus'') that are kept for decorative purposes in outdoor koi ponds or water gardens. Koi is an informal name for the colored variants of ''C. rubrofuscus'' ke ...

and

Nguni Nguni may refer to: *Nguni languages *Nguni cattle *Nguni people *Nguni sheep, which divide into the Zulu sheep, Zulu, Pedi (sheep), Pedi, and Swazi sheep, Swazi types *Nguni stick-fighting * Nguni shield * Nguni homestead *Nguni (surname) {{disam ...

fish. The distinct polymorphism is not seen in the introduced population in Lake Otjikoto. It is very closely related to the

banded tilapia ''Tilapia sparrmanii'', the banded tilapia, or vlei kurper, is a widespread and adaptable cichlid fish that is found in warmer freshwater habitats of southern Africa. They prefer water with ample plant cover, and occur naturally as far north as D ...

(''T. sparrmanii'') and the two species can

interbreed In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in ...

References

External links

* Photographs
Pinkish ("koi") individualOlive (yellow) morphBlue morph
Otjikoto tilapia Cichlid fish of Africa Freshwater fish of Namibia Endemic fauna of Namibia Fish described in 1936 Taxonomy articles created by Polbot {{Tilapiini-stub