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This study highlights the value of museum collections in invasion biology. It focuses on introduced tilapias, Oreochromis niloticus and Coptodon rendalli in the Congo Basin and their monogenean (Platyhelminthes) gill parasite fauna. O. niloticus was introduced throughout the Congo Basin while C. rendalli was introduced into the Lower Congo, but is native to the Middle and Upper Congo. In order to study the impact of these stocking events on the native parasite community we investigate the co-introduction and host switching of their parasites. Post-introduction material is compared with pre-introduction samples from museum collections of 5 native tilapias in the Congo Basin. Nine of the known parasites of O. niloticus were co-introduced, while one, Cichlidogyrus rognoni, is missing and possibly not established. In contrast, no parasite species were found co-introduced with C. rendalli into the Lower Congo. The parasite fauna of Tilapia sparrmanii shared no species with O. niloticus. Oreochromis mweruensis shared five species with O. niloticus, but these were also found on the pre-introduction samples, and are considered native to both hosts. We report three putative host switches: Cichlidogyrus sclerosus and Cichlidogyrus tilapiae to Coptodon tholloni in the Lower Congo Basin and Gyrodactylus nyanzae to C. rendalli in the Upper Congo. [ABSTRACT FROM AUTHOR]

In this study, morphological differences were found that corroborate earlier results that showed the existence of six species within the previously monospecific African pike genus Hepsetus. Additional genetic data ( coI, mtDNA and rag1, nDNA) confirm the morphology-based species delineations. Deep genetic divergences imply a relatively old age for diversification within the genus. An identification key for the six species is provided in the present study. [ABSTRACT FROM AUTHOR]

Labeo rosae, a species with a native range in Southern Africa, was discovered in the Congo basin by re-identification of two museum specimens previously identified as Labeo mesops. The occurrence of this species in the upper Congo implies a range extension of the species of more than 1000 km. Although the species' distribution is mirrored by that of some other Cypriniformes, its occurrence in the Congo might be due to introduction by humans. [ABSTRACT FROM AUTHOR]

An α-taxonomic revision of the African pike, Hepsetus odoe, from Lower Guinea is provided. The results show that three different species occur in Lower Guinea instead of one. Hepsetus akawo, recently described from West Africa, is present in the northern part of Lower Guinea; Hepsetus lineata, the most widespread species within Lower Guinea, is known from the Sanaga (Cameroon) in the north to the Shiloango ( Democratic Republic of the Congo) in the south and Hepsetus kingsleyae sp. nov. is endemic to the Ogowe Basin. The new species H. kingsleyae is described and H. lineata, which is elevated here to the species level, is redescribed. Hepsetus lineata can easily be recognized by its prominent horizontal line pattern on the flanks and differs further from H. akawo and H. kingsleyae in the number of lateral-line scales and the number of gill rakers. Hepsetus kingsleyae differs from H. lineata and H. akawo by its narrow head, elongated snout and narrow, knife-shaped body. All three species are also distinguishable from H. odoe and the recently revalidated H. cuvieri. A few exceptional specimens could not be allocated to one of the three species and may represent hybrids because of their mixed diagnostic characters or their intermediate values. [ABSTRACT FROM AUTHOR]

Within the genus Hepsetus, a new species from the eastern part of West Africa is described. Hepsetus akawo sp. nov. is mainly distinguished from Hepsetus odoe by a smaller number of lateral line scales [43–51 vs 50–60 (exceptionally 49)] and a shallower head depth [38.0–45.6 (mean 42.0) % head length vs 41.4–49.0 (44.6) % head length] (positively allometric). Hepsetus akawo sp. nov. differs mainly from the recently rehabilitated Hepsetus cuvieri by: a higher number of gill rakers (17–23 vs 8–13); and a lower number of scales between the dorsal fin and the lateral line (7½–9½ vs 10½–11½). Within West Africa, the distribution area of the new species is restricted to the Sassandra River (Ivory Coast) in the west up to the Cross River (Cameroon) in the east. The species is entirely allopatric with H. odoe, which has a far more restricted distribution than previously thought and occurs from the Senegal River (Senegal) in the west to the Cavally River (Ivory Coast) in the east. [ABSTRACT FROM AUTHOR]

Hepsetus cuvieri (Castelnau, 1861), originally described from 'lac N'gami' (Botswana) and synonymized with H. odoe (Bloch, 1794) by Roberts (1984), is revalidated. Hepsetus cuvieri can be readily distinguished from H. odoe based on a lower total number of gill rakers (8-13 versus 14-21); a generally higher number of scales between the dorsal fin and the lateral line (10½-11½ versus 7½-10½) and a higher number of scales between the adipose fin and the lateral line (6½-7½ versus 4½-6½) and other characters. A neotype is designated, as the holotype of this nominal species is apparently lost. Hepsetus cuvieri is restricted to the Quanza, Zambezi ichthyofaunal provinces and the southern part of the Congo Basin, i.e. the Congo ichthyofaunal province. [ABSTRACT FROM AUTHOR]

A detailed morphometric study of 123 specimens identified as Mastacembelus albomaculatus and the six syntypes of M. tanganicae was undertaken. On each specimen, 27 morphometric measurements and 12 meristics were taken. The type series of M. tanganicae contains more than one species, with four specimens attributed to a new species M. reygeli sp. nov. A redescription of M. albomaculatus and a description of the new species are provided. Both species are endemic to the northern and central part of Lake Tanganyika. They can be distinguished based on the number of caudal vertebrae [47–52 (median 49) in M. albomaculatus v. 42–46 (44) in M. reygeli sp. nov.], the total number of vertebrae [85–90 (88) v. 78–83 (81)] and the distance from the snout to the last externally visible dorsal spine (S-LDS) [61·8–67·0 (mean 64·0) v. 66·6–71·5 (68·6)% LS]. In addition, intermediate specimens and populations between M. albomaculatus and M. reygeli were discovered from several parts of the lake, but mainly from the southern part. The latter intermediate populations were provisionally identified as introgressed populations. [ABSTRACT FROM AUTHOR]

Mastacembelus liberiensis of West Africa is discussed with reference to its distribution within the Konkoure River basin (Guinea). The synonymies of M. reticulatus and M. laticauda with M. liberiensis are both confirmed. Further, intraspecific meristic, morphometric and colour pattern variation within M. liberiensis is documented and discussed. Finally, a new species, M. kakrimensis sp. nov., endemic to the Konkoure River basin is identified and described. [ABSTRACT FROM AUTHOR]

A detailed morphometric study was undertaken of collections of the Lake Tanganyika endemic Mastacembelus ophidium. On each specimen 27 measurements and 12 meristics were taken. Within the specimens previously identified as M. ophidium a new species was discovered. A redescription of M. ophidium and a description of the new species are provided. [ABSTRACT FROM AUTHOR]

The family Mastacembelidae is currently divided into two subfamilies, the Mastacembelidae and the Afromastacembelinae. Within the African Afromastacembelinae two genera, Caecomasiacembelus and Aethiomastacembelus, are recognized. Both the subfamily and the African generic division were critically evaluated mainly through X-ray analyses and osteological research. There is no supporting evidence for a split into two subfamilies. In addition, the present diagnosis of the African genera proved to be unworkable, and no convincing phylogenetic evidence supporting this classification is available. Therefore, pending new detailed phylogenetic research, the use of a subfamily classification within the family Mastacembelidae is not recommended. Furthermore, Caecomastacembelus and Afromastacembelus are placed in synonymy with the genus Masiacembelus. [ABSTRACT FROM AUTHOR]