Abstract
BackgroundAfrican catfishes of the families Bagridae and Clariidae are known to be parasitized with monogeneans of Quadriacanthus Paperna, 1961 (Dactylogyridae). The genus remains taxonomically challenging due to its speciose nature and relatively wide host range representing two fish orders, i.e. Siluriformes and Osteoglossiformes, in Africa and Asia. Here, we investigated diversity of Quadriacanthus spp. parasitizing Clarias gariepinus (Burchell), Heterobranchus bidorsalis Geoffroy Saint-Hilaire, and Bagrus docmak (Forsskål) collected in the Lake Turkana (Kenya) and Nile River Basin (Sudan). The interspecific relationships among Quadriacanthus spp. parasitizing catfishes inferred from ribosomal DNA sequences were investigated for the first time.MethodsA combined morphological and molecular approach was used for description of the new species and for a critical review of the previously described Quadriacanthus spp., by means of phase contrast microscopic examination of sclerotized structures, and assessing the genetic divergence among the species found using rDNA sequences.ResultsSeven species (including four new) of Quadriacanthus were identified. These were as follows: Quadriacanthus aegypticus El-Naggar & Serag, 1986, Quadriacanthus clariadis Paperna, 1961, Quadriacanthus fornicatus n. sp., Quadriacanthus pravus n. sp., and Quadriacanthus zuheiri n. sp. from Clarias gariepinus (Clariidae); Quadriacanthus mandibulatus n. sp. from Heterobranchus bidorsalis (Clariidae); and Quadriacanthus bagrae Paperna, 1979 from Bagrus docmak (Bagridae). For both 18S-ITS1 and 28S rDNA regions, Q. clariadis from a clariid fish was found to be most closely related to Q. bagrae from a bagrid host. Quadriacanthus mandibulatus n. sp. was observed to be the most distant species from the others. The separation of Q. mandibulatus n. sp. from the other species corresponds with the different morphology of its copulatory tube. The copulatory tube is terminally enlarged in Q. mandibulatus n. sp., while the tube in all other congeners studied is comparatively small and with an oblique tapering termination.ConclusionsThis study contributes to a better understanding of African dactylogyrid diversity and provides the first molecular characterization of Quadriacanthus spp. The observed interspecific genetic relationships among Quadriacanthus spp. from clariids and Q. bagrae from a bagrid host suggest a possible host-switching event in the evolutionary history of the genus. Our records extend the currently known geographical range for Quadriacanthus spp. to Kenya and Sudan.
Highlights
African catfishes of the families Bagridae and Clariidae are known to be parasitized with monogeneans of Quadriacanthus Paperna, 1961 (Dactylogyridae)
This study contributes to a better understanding of African dactylogyrid diversity and provides the first molecular characterization of Quadriacanthus spp
Clariid catfishes most likely originated in Asia 40–50 MY ago but contemporary African and Asian species originated from a common ancestor that was present on the Arabian plate about 15 MY ago [38]
Summary
African catfishes of the families Bagridae and Clariidae are known to be parasitized with monogeneans of Quadriacanthus Paperna, 1961 (Dactylogyridae). Quadriacanthus Paperna, 1961 (Dactylogyridae) represents one of the genera with wider host and geographical distribution This genus comprises mostly gill parasites of African and Asian clariids (Siluriformes, Clariidae), one species has been recorded on bagrids (Siluriformes, Bagridae) and one species on phylogenetically distant notopterids (Osteoglossiformes, Notopteridae) in Africa [2, 3]. Despite the work of these authors, Dubey et al [6] established Anacornuatus Dubey, Gupta & Agarwal, 1992 for those species of Quadriacanthus that possess a two-piece ventral bar instead of a single-piece ventral bar, as indicated by Paperna [4] They were unaware of the work of Kritsky & Kulo [5] and erred in proposing the new genus. This finding extends the host range of species of Quadriacanthus to a new family (Notopteridae) and even a new order (Osteoglossiformes)
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