Nanochromis Pellegrin

[[Genus Nanochromis Pellegrin]]

Species diversity among the Congolese cichlid genus Nanochromis Pellegrin is poorly known, despite the fact that the first species was described more than a century ago and that the group has since attracted considerable attention from the aquarium hobby. The genus was erected by Pellegrin (1904) for the type species nudiceps Boulenger, 1899 as a replacement name for the preoccupied Pseudoplesiops Boulenger, 1899. As currently understood, Nanochromis belongs to a monophyletic group of African cichlids informally named the chromidotilapiines, and is diagnosed by the possession of a characteristically reduced infraorbital series, and an elevated lateral line that is posteriorly contiguous with the dorsal fin base (Greenwood 1987). Five of the nine described Nanochromis are known only from the region of the lower Congo rapids between the Malebo Pool and the town of Inga. However, the locality of the type species N. nudiceps, is “Kutu”, a small Congolese town located in the inner Congo basin (“Cuvette Centrale”) at the junction of the outlet of Lake Mai Ndombe (formerly Lake Leopold II) with the Lukenié-Fimi River, an affluent the Kasai River. More than eighty years after the description of the first species from the inner Congo basin, a second species, N. transvestitus, was described from the southern end of Lake Mai Ndombe close to the village of Ipeke (Roberts & Stewart 1984). The first ichthyological collection in the northern and main part of the lake basin in the vicinity of the town of Inongo was undertaken by the first author (UKS) during a survey in August/ September 2002. This collection yielded several Nanochromis transvestitus, numerous Nanochromis cf. dimidiatus and a small number of individuals of a highly distinctive Nanochromis which is described herein.