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Pseudocrenilabrus pyrrhocaudalis sp. nov. is described from Lake Mweru in the upper Congo River drainage, on the border of the Democratic Republic of Congo and Zambia. This species, which appears to be endemic to the lake, lives in sympatry with P. philander. Pseudocrenilabrus pyrrhocaudalis sp. nov. is distinguished from P. philander in nuptial males by the presence of an orange colour on the ventral part of the body and the proximal parts of the anal and caudal fins, a broad band of bright white on the distal edge of anal and caudal fins, a uniform grey head and dorsum, and a subtruncate caudal fin. In addition, P. pyrrhocaudalis has a shorter snout, a narrower head, a smaller interorbital distance, a smaller pre-anal distance, a more slender caudal peduncle and fewer scales around the caudal peduncle in both sexes.

Fishes normally restricted to inland waters are valuable model systems for historical biogeography, inter alia, because of their limited dispersal abilities and concordance with the distribution patterns of other freshwater taxa (Zogaris et al. 2009). The comparison of fish species assemblages has been the major biogeographical tool for delineating African aquatic ecoregions as the fossil record is often meagre and merely offers complementary information. This is, for example, the case for the Zambezian and Congolian ichthyofaunal provinces, which display substantial contemporary fish diversity (Stewart 2001). Between both regions lies the Bangweulu-Mweru ecoregion (sensu Scott 2005), known for its high percentage of endemicity. Although hydrographically belonging to the Congo Basin, the Bangweulu-Mweru ecoregion has a high affinity with the Zambezi province (Scott 2005), due to historical river connections (Tweddle 2010). Studies comparing the Zambezi and Congo ichthyofaunal provinces are rare and hampered by lack of data from the Congo Basin. The latter harbours more than 1250 fish species (Snoeks et al. 2011) while in the Zambezi, only 120 freshwater fishes are found (Tweddle 2010). Indeed, species richness declines in all major African teleost families from the Congo Basin southwards, riverine haplochromine cichlids forming a notable exception to this rule (Joyce et al. 2005). Although it was hypothesized by Tweddle (2010) that the origin of many Zambezian fish species is in the Congo Basin, the haplochromines Serranochromis Regan, Sargochromis Regan, Pharyngochromis Greenwood and Chetia Trewavas, together forming the serranochromines, have their centre of diversity in the rivers of the Zambezian ichthyofaunal province (Joyce et al. 2005). Therefore, the biogeographical history of Cichlidae across the Zambezi- Congo watershed is not only key to cichlid biogeography on an African scale, but also complementary to biogeography of all other teleosts in the region. Yet, colonisation and speciation patterns are difficult to unravel due to complex hydrological history (Katongo et al. 2007; Schwarzer et al. 2012).

Barbus teugelsi, a new African cyprinid, is described from the Mongo River at Marela (Guinea). It is morphologically similar to the syntopically occurring ‘B.’ bigornei Leveque et al. 1988, with which it has been confounded in the past. However, the scale meristics of the new species differ from those of ‘B.’ bigornei, but are similar in all but one to those of ‘B.’ ablabes (Bleeker 1863) and ‘B.’ parablabes Daget 1957. Barbus teugelsi sp. nov. is clearly distinguished from both these species by the following unique combination of characters: a lower total number of gill rakers on the first gill arch (3–6); the presence of long barbels, with the anterior barbels reaching the vertical passing through the middle of the eye and the posterior barbels extending beyond the vertical passing through the posterior edge of the eye and reaching the pre-operculum. In addition, the cephalic sensory canals are highly reduced or even absent. Furthermore, small differences between the new species and the other three species were found for several measurements. A short discussion on the taxonomic value of some diagnostic characters in small barbs is included.

Intraspecific morphological variation in Neolamprologus niger from seven localities along the north-western shoreline of Lake Tanganyika (Luhanga, Bemba, Ubwari West, Ubwari East, Yungu, Kabimba and Kalemie) was investigated. As a result of geographical variation, the populations could be categorized into a northern, a central and a southern group. A clear clinal pattern was found for several meristics and measurements. The lack of knowledge on the geographical variation in African cichlids and its implication for further taxonomic research is discussed.