Morphological and molecular characterization of Glossidium pedatum Looss, 1899 and Orientocreadium batrachoides Tubangui, 1931 from sharptooth catfish,Clarias gariepinus (Burchell, 1822)

The superfamily Plagiorchioidea has a considerable number of genera and species with great uncertainty of their phylogenetic position. The objectives of the current study were to specifically describe the morphology and determine for the first time the phylogenetic position of Glossidium pedatum and Orientocreadium batrachoides. Examination of G. pedatum using conventional light and scanning microscopy techniques revealed undescribed features related to the digestive system, the presence of papillae-like lateral lappets, and terminal lobes covered with backwardly directed spines. Orientocreadium batrachoides revealed a pharynx that is four lobed anteriorly. Both the large (28S) and small (18S) subunits of the ribosomal genome, analysed through Bayesian inference and maximum likelihood, were used to genetically characterise these species. Phylogenies indicate that G. pedatum does not fit well into any known family within the Plagiorchioidea, as currently indicated in various systematic structures based on morphology. However, G. pedatum was closely related to Haematoloechidae according to analyses of 18S and 28S rDNA. Based on 28S rDNA, O. batrachoides formed a well-supported clade with Orientocreadium pseudobagri within the family Orientocreadiidae. In turn, Orientocreadiidae is closely related to Leptophallidae. The current study provides essential information that could be helpful to assign the family for Glossidium in future studies. Characterisation of life-cycle stages may be necessary to fully elucidate the systematic position of G. pedatum.