Rhabdias aegyptiaca El-Garhy & Garo, 2006 (Nematoda: Rhabdiasidae), parasitic in Sclerophrys regularis (Reuss) (Anura: Bufonidae) with a preliminary treatment of the problematic taxonomic status of North African Rhabdias

The taxonomic ambiguity of North African Rhabdias Stiles & Hassall, 1905 requires a deep revision and re-evaluation to define the genuine taxa. Based on newly gathered specimens, the African/Saharo-Arabian Rhabdias aegyptiaca El-Garhy & Garo, 2006 is redescribed for specimens collected from the lungs of the common African toad, Sclerophrys regularis (Reuss) (Anura: Bufonidae) from Egypt, northeast Africa. The species characterization is investigated through detailed morphology using light and scanning electron microscopy, as well as in-depth morphological and morphometric comparisons against closely related Rhabdias spp. The problematic morphological/taxonomic status of the original description of R. aegyptiaca is elucidated, discussed, and treated. Additionally, species identification is confirmed by genetic divergence, phylogenetic, and species delimitation analyses using the mitochondrial gene (cox1 mtDNA) and ribosomal genetic markers (28S rDNA + ITS rDNA). Rhabdias aegyptiaca differs from other African congeners in the combination of the following characteristics: truncate anterior end, buccal capsule 1117 (15 0.4) m wide, four submedian circumoral lips with two lateral pseudolabia, esophagus with dilatation at end of first third and tail wholly covered with inflated cuticle except for its end tip. Present investigations on the validity of the Saharo-Arabian record of R. africanus sensu Abdel-Hakeem, Fadladdin, El-Sagheer & Adel, 2022 regard it as another record of R. aegyptiaca. The confusing status of the Saharo-Arabian record of Rhabdias bufonis sensu Morsy, Mohamed, Abdel-Ghaffar, Fayoumi & Abdel-Haleem, 2018 is discussed and assigned as belonging to another genus, Thubunaea Seurat, 1914. Rhabdias bufonis sensu Moravec, Baru & Ryav, 1987 is considered a highly likely stand-alone Saharo-Arabian species, distinguished from the complex of Rhabdias bufonis (Schrank, 1788) Stiles & Hassall, 1905 by its pre-equatorial vulva, and largely sized buccal capsule and eggs. However, their specimens still need futural re-investigation for an appropriate description and designating type specimens.