Insights into the phylogenetic position of genus Synodontella (Monopisthocotylea) among some other Dactylogyridea gill parasites of African catfishes and the importance of haptoral elements

Abstract

This work provides new molecular data on seven species representing three genera (Protoancylodiscoides, Schilbetrema and Synodontella)  in the order Dactylogyridea. The results help to explain the origin of Synodontella spp. and to elucidate the phylogenetic position of   Synodontella in relation to the other genera. The findings also highlight the importance of the haptoral elements in determing  phylogenetic relationships between and within Dactylogyridea taxa, which are monogenean parasites of mostly cyprinid fishes in fresh  water. A total of 36 catfish specimens representing five species in three genera (Synodontis, Schilbe and Chrysichthys) were collected from two rivers in Cameroon: the Sanaga River (at Edéa and Nachtigal, in the Littoral and Cental regions, respectively) and Boumba River (at  Mang-kaka, East Region), and examined for gill parasites. The novel 28S rDNA sequences of seven species belonging to Dactylogyridea  were obtained and their phylogenetic relationships inferred. Synodontella resulted as a monophyletic lineage; the samples obtained from  the catfish in Cameroon were well-differentiated into two groups. Synodontella appears to be more closely related to Schilbetrema  than to the other Dactylogyridea species investigated here. The shape of the ventral bar should be considered an important feature for  distinguishing among Dactylogyridea genera. The existence of two or more lineages within the genus Synodontella, as suggested by  previous morphological studies, is here molecularly confirmed, indicating speciation as likely an outcome of ecological influences or the  phylogenetic relationships among parasites and/or hosts.