Saturday 26 January 2013

Two new species of Cichlid Fish from Lake Victoria.

Cichlid Fish are widespread freshwater Perch (Perciformes), found in Africa, South America, southern North America, parts of the Caribbean, Madagascar, the Middle East and South Asia. There are one of the most diverse Fish, and therefore Vertebrate, families, with over 1600 described species. They are popular in the aquarium trade, which has led to them becoming naturalized in many parts of the world where they are not native.

In a paper published in the journal ZooKeys on 2 January 2013, a team of scientists led by Marnix de Zeeuw of the Naturalis Biodiversity Center in Leden describe two new species of Cichlid Fish from the waters of southern Lake Victoria. Neither of these is, strictly speaking, new to science, but neither has been formally described before.

The first species described is named Haplochromis argens, it has appeared previously in numerous scientific publications under the name Haplochromis 'argens' (argens meaning silver) from the 1970s onwards, but has never actually been properly described. Haplochromis argens is a 53-78 mm, slender Cichlid Fish. Males have a blue-to-purple sheen on their upper sides and a yellow-to-green sheen on their flanks, as well as reddish fins with spots on the anal fin. They consume zooplankton in the photic zone (top part of the water that light can penetrate), being restricted to the top two meters at night, but foraging deeper at night. The species was abundant in the Mwanza, Speke and Emin Pasha Gulfs and around Kome Island until the 1980s, but suffered a collapse in population due to the introduction of Nile Perch (Lates niloticus) to the lake, and have not recovered despite the success of measures to reduce the Nile Perch population. The species is also well known in the aquarium trade.

Haplochromis argens; (top) male specimen from Emin Pasha Gulf, (middle) male specimen from Mwanza Gulf, (bottom) line drawing. Scale bar is 10 mm. de Zeeuw et al. (2013).

The second Cichlid Fish is named Haplochromis goldschmidti; it has previously been known as Haplochromis 'dusky argens', and is now named after Tijs Goldschmidt, the scientist who first referred to the Fish, and an expert on the Cichlids of Lake Victoria who has studied both their ecology and evolution, and the extinction event they suffered as a result of the introduction of the Nile Perch. It is similar to H. argens, but darker and with a curved profile. It is known only from Emin Pasha Gulf; it is unclear if the species survives.

Haplochromis goldschmidti; (top and middle) male specimens, (bottom) line drawing of male specimen. Scale bar is 10 mm. de Zeeuw et al. (2013).

Southern Lake Victoria. (A) The known distribution of Haplochromis argens (crosshatched area). (B) Area where Haplochromis argens specimens were collected in Mwanza Gulf. Letters indicate the locations of research stations. (C) Locations where specimens were collected in Emin Pasha Gulf. Circles are for H. argens, triangles for H. goldschmidtide Zeeuw et al. (2013).

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