GASTROINTESTINAL HELMINTHS OF THE FRANCISCANA Pontoporia blainvillei (MAMMALIA: CETARTIODACTYLA) IN THE NORTHERN COAST OF RIO GRANDE DO SUL STATE, SOUTHERN BRAZIL

Abstract

The franciscana, Pontoporia blainvillei (Gervais & d'Orbigny, 1844), is an endemic dolphin species from the southwestern Atlantic, occurring exclusively in coastal waters of Brazil, Uruguay and Argentina. This species is considered threatened with extinction at both global and regional levels and is listed as "Critically Endangered" (CR) according to the IUCN criteria in the state of Rio Grande do Sul (RS), southern Brazil. The franciscanas from RS and Uruguay are considered to be part of the same management stock, defined as Franciscana Management Area III (FMA III). This study evaluated the helminths of the stomach of 34 specimens of franciscana, incidentally caught in fishing nets or stranded in the northern coast of RS, between 1993 and 2010. Additionally, the helminths found in the small and large intestines of four of those specimens were also analyzed. Although six parasite taxa have been identified, based on infection levels and reproductive status, three of them were considered as the most important helminths of franciscanas: Anisakis typica, Corynosoma cetaceum and Synthesium pontoporiae. The parasite assemblages and the parasitological indices were different from those reported in the literature for southern RS (i.e., Rio Grande). The most striking differences between the two areas were the lower prevalence of C. cetaceum as well as the absence of C. australe in the dolphins from northern RS. Based on these findings, we hypothesized the existence of an ecological differentiation on the helminthfauna of franciscanas inside the FMA III.