Integrative taxonomy reveals hidden cestode diversity in Pimelodus catfishes in the Neotropics

Proteocephalid tapeworms are the dominant group of endoparasites in siluriform catfishes in South America, but their interrelationships and actual diversity remain poorly understood. Molecular prospecting of proteocephalids found in pimelodid and other catfishes, especially in Pimelodus spp., along with thorough morphological evaluation, revealed high species diversity of these parasites. Using newly obtained sequences of the partial large subunit nuclear ribosomal RNA (lsrDNA) and complete mitochondrial cytochrome c oxidase subunit I (COI), phylogenetic relationships of the cestodes of Pimelodus catfishes were assessed and a new genus, Pseudoendorchis gen. n., proposed to accommodate Pseudoendorchis auchenipteri comb. n. (type species; formerly Endorchis auchenipteri), Pimelodella cristata sp. n. from Pimelodella cristata (Heptapteridae), Pimelodella felipei sp. n. from Pimelodus fur, Pimelodus souzalimae sp. n. from Pimelodus maculatus and another three putative new species. Members of the new genus can be readily distinguished from all known Neotropical proteocephalids by having a large Mehlis' gland, representing at least 18% of proglottid width, and the vagina always anterior to the cirrus-sac. Moreover, all phylogenetic, species discovery and validation analyses support validity of Pseudoendorchis. Combining the lsrDNA + COI sequence data appeared to provide the best resolution in phylogenetic analyses, which may be useful to reduce the uncertainty of the interrelationships among Neotropical proteocephalids.