Cucullanus pinnai pinnai and C. pinnai pterodorasi (Nematoda Cucullanidae): what does the integrative taxonomy tell us about these species and subspecies classification?

Cucullanus pinnai has been divided in two subspecies (C. pinnai pinnai and C. pinnai pterodorasi) based on the morphology of oesophastome. While C. pinnai pinnai apparently shows low host specificity and broad geographic occurrence, with certain morphological variations, C. pinnai pterodorasi was reported once, parasitizing Pterodoras granulosus. We used an integrative taxonomic approach to evaluate whether or not populations of C. pinnai pinnai from Trychomycterus spegazzinii (Escoipe River, Argentina) and Pimelodus fur (Miranda River, Brazil), and of C. pinnai pterodorasi from Pterodoras granulosus (Miranda River, Brazil) are conspecific. Parasites were observed using light microscopy and genetically characterized based on partial sequences of the 18S and 28S rDNA, ITS1-5.8S-ITS2, and COI mtDNA. Phylogenies were reconstructed and the Generalized Mixed Yule Coalescent (GMYC), Poisson Tree Process (bPTP), and Automatic Barcode Gap Discovery (ABGD) were used for species delimitation purposes. The present samples formed well-supported monophyletic assemblages, corroborating in part the results of morphological analyses; however, they grouped according to geographic origin. Species delimitation suggested conspecificity of C. pinnai pinnai with C. pinnai pterodorasi from Brazil; consequently, the morphology of oesophastome may be an intraspecific variation. Results also indicated that C. pinnai may represent a species complex as samples from Argentina were suggestive of an independent specific entity. However, definitive affirmations are premature, since there is no autapomorphy for separating C. pinnai from Brazil and Argentina and sampling was limited to three host species from two river basins. The phylogenetic reconstructions also confirmed the artificiality of some genera within Cucullanidae.

Integrative taxonomy of Sprentascaris mahnerti and phylogeny of raphidascaridid nematodes (Nematoda: Ascaridoidea: Raphidascarididae) suggest the monophyly of Sprentascaris.

Sprentascaris mahnerti (Nematoda: Raphidascarididae) collected from Loricariichthys labialis (Siluriformes: Loricariidae) in the Pantanal wetlands, State of Mato Grosso do Sul (Brazil), was redescribed using light and scanning electron microscopy (SEM), and genetically characterised along with two other raphidascaridids: Raphidascaroides brasiliensis and Ro. moraveci. Due to the systematic discussion regarding Raphidascaris and Sprentascaris, as well as the poor knowledge about the phylogenetic relationships within Raphidascarididae, phylogenies were reconstructed based on partial sequences of the 18S and 28S nuclear rRNA gene, the nuclear ITS1-5.8S-ITS2 and the cytochrome c oxidase subunit I (cox1) mtDNA. Morphological study of S. mahnerti, confirmed some previously described features, revealed new characteristics and permitted to elucidate some inconsistencies noted in the literature. Morphological and genetic characterisation of S. mahnerti supported its validity. Phylogenetic reconstructions supported the monophyly of Sprentascaris, which has three pairs of interlabial conspicuous cuticular projections as a synapomorphy. The relationships among several lineages of raphidascaridids were unsolved, albeit Goezia and Ichthyascaris formed well-supported monophyletic assemblages, in which the first included species with no relations regarding the habitat of hosts and the geographic origin. The present findings represent one more step towards the understanding of the interrelationships of raphidascaridid nematodes. In this sense, Sprentascaris should be considered valid as an independent lineage from Raphidascaris.