The ichthyofauna of Lake Tanganyika consists of 12 families of fish of which five belong to Siluriformes (catfishes). Studies on Siluriformes and their parasites in this lake are very fragmentary. The present study was carried out to help fill the knowledge gap on the monogeneans infesting the siluriform fishes of Lake Tanganyika in general and, more particularly, Clarias gariepinus. Samples of gills of Clarias gariepinus (Clariidae) were examined for ectoparasites. We identified the monogenean Gyrodactylus transvaalensis (Gyrodactylidae). This is the first time this parasite was found infecting gills. We are the first to observe a large spine in the male copulatory organ of this species and to provide measurements of its genital spines; this completes the description of the male copulatory organ, which is important in standard monogenean identification. This is the first monogenean species reported in C. gariepinus at Lake Tanganyika and the third known species on a representative of Siluriformes of this lake. It brings the total number of species of Gyrodactylus recorded in Lake Tanganyika to four. Knowing that other locations where this species has been reported are geographically remote from Lake Tanganyika, we propose a “failure to diverge” phenomenon for G. transvaalensis.

In the Upper Congo Basin, there are few records of monopisthocotylan parasites from clariids. More surveys of clariid fishes can lead to the discovery of multiple monopisthocotylan species that are new to the region or new to science. We aimed to investigate the monopisthocotylan parasite fauna belonging to Quadriacanthus of five clariid fishes in the Upper Congo Basin by (i) inventorying the species composition and providing the description of new species when necessary, and (ii) analysing their infection parameters. Clarias ngamensis, C. stappersii, C. buthupogon, C. gariepinus and C. theodorae were purchased from fishermen in the Lufira, Lubumbashi and Kafubu rivers in the Upper Congo Basin. Monopisthocotylans were mounted on glass slides with ammonium picrate-glycerin for identification based on morphological analysis of genital and haptoral sclerotised parts. Eight species, namely Q. aegypticus, Q. allobychowskiella, Q. amakaliae, Q. domatanai, Q. halajiani, Q. kalomboi n. sp., Q. bassocki n. sp. and Q. shigoleyae n. sp. are reported. The most prevalent parasite species was Q. amakaliae on C. stappersii (prevalence 60%) with a mean infection intensity of 9.8 ± 7.7. We report C. stappersii and C. buthupogon as new hosts for species of Quadriacanthus as well as three new parasite species for science and new localities for the first five parasite species mentioned above. The new records and the description of Q. kalomboi n. sp., Q. bassocki n. sp. and Q. shigoleyae n. sp. increase the knowledge of the diversity of monopisthocotylans in this region.

In spite of the global barcoding effort, there is still a lack of genetic data on African freshwater fishes. We aimed to contribute to bridging this gap by providing molecular data on commercially important catfish species from the north-western part of Lake Tanganyika. We collected 215 catfish specimens and sequenced the standard vertebrate barcoding gene (COI) for 41 specimens. Additionally, we sequenced 20 specimens for the mitochondrial Cyt-b gene to make the link to previously published datasets. We identified 11 species using morphology, compared DNA sequences with those available on GenBank, and employed Automatic Barcode Gap Discovery (ABGD) and phylogenetic approaches. The dataset includes the first molecular data (COI and Cyt-b) for Chrysichthys acsiorum, as well as the first-ever COI sequences for Dinotopterus cunningtoni and Malapterurus tanganyikaensis. Our findings extend the known distribution of C. acsiorum by approximately 100 km. Additionally, we demonstrated the difficulty in delineating species of Chrysichthys and Synodontis from Lake Tanganyika with molecular tools. For Chrysichthys, automated methods, such as ABGD, failed to delineate species. However, barcoding does seem promising as all the individual species are resolved as clades. Within Synodontis, the study found a strong similarity between S. grandiops and S. multipunctatus, highlighting a need for revision. Our findings emphasize the necessity for integrative taxonomy in the study of catfishes from Lake Tanganyika.