First molecular characterization and species validation of Toxocara alienata (Rudolphi 1819) (Nematoda: Ascarididae), from a crab-eating raccoon (Procyon cancrivorus)

Abstract

Toxocara alienata infects racoons and wild pigs in South America and its taxonomy is important to distinguish thespecies from closely related zoonotic congeners, such as T. canis. This study provides the first genetic characterizationof T. alienata from the Brazilian Amazon, along with a comprehensive morphological description, toclarify its distinction from the closely related T. canis. Nematodes were observed using light and scanningelectron microscopy and genetically characterized based on barcode COI mtDNA. A phylogeny was reconstructedusing Bayesian inference and different species delimitation methods (PTP, bPTP, ASAP, GMYC) were performedfor robust species validation. Specimens were identified as T. alienata based on a somewhat narrow cervical alae;male with equal, alate spicules, shorten than 1 mm, 28 pairs of caudal papillae (24 subventral precloacal pairsand 4 postcloacal pairs) and a protruded well-developed precloacal lip with an unpaired papilla on it, which wasobserved for the first time in the species. These morphological features can differentiate T. alienata from T. canismainly regarding number and arrangement of postcloacal papillae, structure of precloacal lip and the presence ofthe unpaired papilla. In the phylogeny, T. alienata represented an independent lineage, sister to a clade formed byT. canis sequences. All species delimitation methods validated T. alienata as a specific entity, different fromT. canis. The present results, including the first genetic characterization of T. alienata, reinforce its validation andprovide crucial data for future taxonomic, epidemiological and ecological works on Toxocarinae.