African catfishes and their monogenean gill parasites: barcoding, diversity and biogeography

Abstract

Africa is one of the regions with a high concentration of aquatic biodiversity. This continent also has many scientifically underexplored areas, which means there is still much to be done regarding research on aquatic biodiversity. To contribute to this topic, we focused on three families of economically important catfishes that are widely distributed across several ichthyological provinces of the African continent: Auchenoglanididae, Bagridae, and Clariidae. Our results provide the first available COI and/or Cyt-b sequences for three species of catfishes collected from Lake Tanganyika: Chrysichthys acsiorum (COI and Cyt-b), Dinotopterus cunningtoni (COI) and Malapterurus tanganyikaensis (COI). We also provide the first-ever genetic data for any member of Bagrobdella (28S rDNA and 18S-ITS1 sequences of Bagrobdella vanhovei and B. vansteenbergei) and for Quadriacanthus aegypticus (28S rDNA sequences). In this study, we present seven new records of monogeneans (B. anthopenis, B. fraudulenta, B. vanhovei, B. vansteenbergei, Q. aegypticus, Macrogyrodactylus clarii, M. karibae). Bagrobdella vanhovei and B. vansteenbergei are reported for the first-time outside of Lake Tanganyika. These two species are now known to occur throughout the Congo Basin in the Democratic Republic of the Congo (DRC). Bagrobdella fraudulenta only occurs in the ichthyological province of Nilo-Sudan: in the Niger River in Bamako, Mali, and in Lake Albert, in Uganda. This is the first time it is also reported from the Congolese side of Lake Albert. Quadriacanthus aegypticus and Macrogyrodactylus karibae, already known from the DRC, are reported for the first time in Lakes Kivu and Tanganyika, respectively. This is also the first time that Macrogyrodactylus clarii is recorded in the ichthyological province of the Congo. We described a new species of Quadriacanthus: Q. lindiensis. We estimate that at least 500 monogenean species parasitising African catfishes remain undescribed. We found that Auchenoglanis occidentalis requires a taxonomic revision as it is composed of at least three groups/potential species: one restricted to the Congolese province, another confined to the Upper Guinea province, and the third present throughout the Nilo-Sudanese province. We combined DNA barcoding of the host with a screening of its monogenean parasites to reconstruct the evolutionary history of Clarias gariepinus. The populations of C. gariepinus in Lakes Kivu and Edward share COI sequences, suggesting that the evolutionary origin of this fish may be the paleolake Obweruka, which formerly encompassed Lakes Kivu, Edward, and Albert. Among these three lakes, we only found monogenean parasites on the population of C. gariepinus from Lake Kivu. This population found to be parasitised by two only species of monogeneans: Q. aegypticus and M. clarii. Given the poor parasite fauna in these populations of origin, we hypothesize that the current gill parasite fauna of this wide-spread fish built up via lateral transfer as it spread throughout the continent. The state of taxonomy of monogeneans parasitising African catfishes is advancing. We noted that 67% of the first authors currently active in describing new species of monogeneans from African catfishes are early-career researchers based in Africa.