Sistemática das espécies de Oligacanthorhynchus Travassos, 1915 (Acanthocephala: Oligacanthorhynchidae)

Abstract

The Acanthocephala have gaps in the description and taxonomy of their species. These animals are characterized by being parasites of vertebrates and invertebrates, having a lacunar system, a proboscis with hooks in the anterior region of the body and the absence of a digestive system. These parasites are divided into four classes: Eoacanthocephala, Palaeacanthocephala, Polyacanthocephala and Archiacanthocephala. The genus Oligacanthorhynchus currently has 31 species belonging to the order Oligacanthorhynchida, in the class Archiacanthocephala. Among vertebrate hosts marsupials stand out, as they are geographically distributed throughout the New World, and can be parasitized not only by acanthocephalans, but also cestodes, nematodes and trematodes, among other parasites. The general objective of this work was to carry out a taxonomic and systematic study of the genus Oligacanthorhynchus, including the description of a new species, validating or refuting known species and proposing a taxonomic key for the species considered valid for the genus. The new species was found in the small intestine of Didelphis aurita, an endemic species of the Atlantic Forest, in necropsy at the Laboratory of Taxonomy and Ecology of Helminths – Odile Bain (LABTECH), in Juiz de Fora, Minas Gerais, Brazil. The morphology was characterized through Light Microscopy and Scanning Electron Microscopy. The size of the lemnisci, the morphology and morphometry of the eggs and the reproductive structures (cement glands and genital pore) determined the new species was distinct from the other species. In addition, the species of the genus were gathered through descriptions and consultations with specimens deposited in the Helminthological Collection of the Instituto Oswaldo Cruz (CHIOC), Rio de Janeiro, Brazil. The taxonomic status was discussed for each species, determining their validity and proposing diagnostic characteristics for each one. In total, 12 species were classified with a valid differential diagnosis. Eight species were described in juvenile stages and another seven were treated as incertae sedis. Finally, the identification key was elaborated for the valid species. This study was important to expand knowledge of the helminth fauna present in the Atlantic Forest and to provide the first attempt at systematic organization of the genus Oligacanthorhynchus, avoiding ambiguous identification of species and collaborating to advance the taxonomic study of the group.