The aim of this work was to perform a systematic study to detect and quantify the digenetic trematode infections in South American sea lions from the southern Brazilian coast. Twenty-four South American sea lions, Otaria flavescens (Carnivora: Otaridae), were found dead along the coast of Rio Grande do Sul State, Brazil, between June 2010 and September of 2011. Two trematode species were found in the intestines of O. flavescens , i.e., Stephanoprora uruguayense (Digenea: Echinostomatidae) and Ascocotyle ( Phagicola ) longa (Digenea: Heterophyidae). Ascocotyle (P.) longa reached a prevalence of 33.3% and mean intensity of 248,500, whereas S. uruguayense showed a prevalence of 4.2% and mean intensity of 202. The 2 trematode species infecting sea lions were likely transmitted by feeding on mullets, Mugil platanus , that commonly harbor heterophyid metacercariae. The present work is the first report of digenetic trematodes infecting O. flavescens in Brazil. The high prevalence and mean intensity values of the 2 trematode species infecting sea lions in the present study suggest caution in human consumption of mullets and other fish, which can be infected with the metacercariae of these trematodes known to have zoonotic potential.
Scanning electron microscopy was used to analyze superficial features of Gordius dimorphus Poinar, 1991, larvae that might serve as generic or specific diagnostic characters. Three adults of G. dimorphus (2 males and 1 female) were maintained under laboratory conditions until oviposition, which occurred within long strings commonly referred to as egg strings. Larvae have a cylindrical body, annulated and divided into 2 sections, plus an anterior preseptum and a posterior postseptum. Three concentric rings with 6 spines each surround the proboscis. The proboscis is retractile, dorsoventrally flattened, with 1 pair of forceps-like projections on its distal-most portion. On the surface of each projection, 3 pairs of aculeiforms spines are aligned and lean toward the proboscis opening. One large spine is present on the posterior portion of the postseptum. Papillae were not observed. Gordius dimorphus larvae are similar to previous light microscope descriptions. This is the first record of G. dimorphus in Brazil.