Morphological, ultrastructural, and molecular characterization of a new digenean (Plagiorchiidae) found in Osteogaster aenea (Gill) from Brazil

Abstract

The present study aims to describe a new genus and species of a plagiorchid digenean as a parasite of the callichthyid freshwater fish Osteogaster aenea from São Paulo State, Brazil. Detailed morphological analyses using light and scanning electron microscopy, combined with molecular characterization based on partial sequences of the 28S rDNA and COI mtDNA genes, were used to characterize the new species and to describe its phylogenetic position within the Digenea. Atriumlateralis capivarensis n. gen. et n. sp. is characterized by an elongate foliaceous body with smooth tegument, a ventral sucker larger than the oral sucker, obliquely arranged testes, dextral ovary, vitelline follicles arranged in two lateral clustered fields extending intra and extracaecally, and a laterally opening genital pore positioned immediately anterior to the ventral sucker. Phylogenetic analyses consistently recovered the new taxon as a well-supported monophyletic lineage, closely related to Choledocystus hepaticus. This study represents the first record of a mature digenean infecting O. aenea and contributes novel morphological and molecular data to the understanding of plagiorchiid diversity and systematics in Neotropical freshwater fishes.