Taxonomic revision of Rhabdochona (Rhabdochona) esseniae Mashego, 1990 and Rhabdochona (Rhabdochona) gendrei Campana-Rouget, 1961 in Labeobarbus spp. from the Vaal River, South Africa.

内容摘要

During standard parasitological surveys in the Vaal River, South Africa, nematodes were collected from Labeobarbus aeneus (Burchell, 1822) and Labeobarbus kimberleyensis (Gilchrist and Thompson, 1913). No adult nematodes had been reported from these fishes before; thus, the specimens were studied using integrated taxonomic approaches to identify them. This involved combining light microscopy (LM), scanning electron microscopy (SEM), genetic characterisation (18S rDNA, 28S rDNA, and CO1 mtDNA), and multivariate statistical analyses, applying several of these approaches to the same specimen to obtain more holistic information. Two morphotypes were observed and identified as Rhabdochona (Rhabdochona) esseniae Mashego, 1990 and Rhabdochona (Rhabdochona) gendrei Campana-Rouget, 1961. These taxa could be distinguished using several morphological characteristics, some of which have not been previously reported for these species. These included morphology of the vagina, sublabia, mucron, and eggs (revised), which complemented the previously established use of right spicule morphology and left spicule length as characteristic features. Morphological differences between R. (R.) esseniae and R. (R.) gendrei were supported by distinct haplotypes for all gene regions utilised, confirmed through integrated approaches and hologenophore material. Additionally, deirids are reported for the first time for R. (R.) esseniae. Both nematode species were collected from L. aeneus and L. kimberleyensis, with co-infections also observed, representing new host and locality (Vaal-Orange River system) records for R. (R.) esseniae and R. (R.) gendrei. As mixed infections were recorded in both host fishes, and reanalysis of the R. (R.) esseniae type series revealed that a male paratype represented R. (R.) gendrei, the diligent revision of rhabdochonids in Africa is advised. The use of integrative taxonomy, as implemented here, with the same specimen used for microscopy (SEM and LM) and genetic characterisation, was crucial for differentiating taxa and identifying diagnostic morphology in this study and should be considered in future studies of Rhabdochona spp.