Ctenochromis Pfeffer, 1893

Genner, Martin J., Hsu, Ling-Lan, Collins, Rupert A., Smith, Alan M., Saxon, Andrew D., Shechonge, Asilatu H., Ngatunga, Benjamin P. & Turner, George F., 2022, Revision of the African cichlid fish genus Ctenochromis (Teleostei, Cichliformes), including a description of the new genus Shuja from Lake Tanganyika and the new species Ctenochromis scatebra from northern Tanzania, European Journal of Taxonomy 819, pp. 23-54 : 42-43

Genus Ctenochromis Pfeffer, 1893

Type species

Ctenochromis pectoralis Pfeffer, 1893 (by original designation).

Diagnosis

Ctenochromis is a haplochromine cichlid genus restricted to species with the combination of four key characters, following Greenwood (1979): 1) “The abrupt size transition between the very small chest scales and the larger scales on the ventrolateral aspects of the anterior flanks”, 2) “a naked area on either side of the chest”, 3) “a failure of cheek squamation to reach the ventral margin of the cheek”, and 4) “anal fin markings of male fishes are in the form of one or two (rarely three) non-ocellate spots”.

Remarks

As noted by Greenwood (1979: 288), non-ocellate spots are “without a dark margin or clear surround”. In Greenwood (1979) the significance of the non-ocellate male egg spots in the diagnosis of Ctenochromis is unclear, hence a rediagnosis has been provided here. Using the four diagnostic characters for Ctenochromis listed above, the genus currently includes only C. pectoralis and Ctenochromis scatebra sp. nov. described herein.

Of Greenwood’s (1979) five species of Ctenochromis , namely C. pectoralis , C. horei , C. luluae , C. oligacanthus and C. polli, Greenwood notes that three species have non-ocellate egg spots but did not specifically mention which species, although it is likely that Greenwood considered his C. polli to have this trait, given the mention of a colour photograph of the species in Voss (1977: 74). Based on photographs of field collected specimens, or specimens kept in aquaria, we are aware of only one of Greenwood’s five species that unquestionably possesses non-ocellate egg spots, namely the type species C. pectoralis ( Fig. 6 ). Aquarium specimens of Greenwood’s C. horei (herein Shuja horei gen. et comb. nov.) are clearly in possession of ocellate egg spots (see Konings 2015). In contrast to Greenwood, we consider Voss (1977: 74) to show a specimen of Greenwood’s C. polli with an ocellate spot, as does a photograph in Lamboj (2004: 212). There is a photograph of a specimen of C. luluae in Lamboj (2004: 211) with ocellate eggspots. We are unaware of any unambiguous evidence of the precise egg spot characteristics of Greenwood’s C. oligacanthus . Hence, we follow Daget et al. (1991) and Fricke et al. (2021) in assigning Greenwood’s C. polli , C. luluae and C. oligacanthus to the catchall genus Haplochromis , as Haplochromis polli , Haplochromis luluae and Haplochromis oligacanthus , respectively. These three taxa will require a comprehensive taxonomic evaluation. In addition, the specimens we observed of Shura horei gen. et comb. nov. do not possess the “naked area on either side of the chest” characteristic of Ctenochromis , but instead have a single scaleless area at the anterior of

the chest. This single scaleless area at the anterior of the chest is also shared with the phylogenetically proximate Gnathochromis pfefferi .

Figures

Fig. 6. a. Ctenochomis pectoralis Pfeffer, 1893, lectotype ZMH402 from Korogwe (imaged by Thilo Weddehage). b. C. pectoralis, paralectotype BMNH 1899.2.27.1 from Korogwe. c. C. pectoralis, ♂ from Ruvu River shortly after capture (part of BMNH 2021.7.15.1-3). d. C. pectoralis, ♂ from Ruvu River preserved state (part of BMNH 2021.7.15.1-3). e. C. scatebra Genner, Ngatunga & Turner sp. nov., ♂ from Chemka Springs shortly after capture (part of BMNH 2021.7.15.1-3). f. C. scatebra sp. nov. holotype BMNH 2021.7.15.4. Scale bars: 10 mm.