Population structure of the nematode Contracaecum pelagicum johnston & mawson, 1942 during the winter migration of the magellanic penguin Spheniscus magellanicus (Forster, 1781) in Southern Brazil

Abstract

Magellanic penguins, Spheniscus magellanicus, are frequently found along the coast of Brazil during the winter migration. However, there are very few ecological studies of the parasite fauna of these birds, especially of the adults, which are found dead on Brazilian beaches. Moreover, no studies of parasites of the Magellanic penguins found on the Brazilian coast have evaluated adult or larval nematodes during winter migration so far. Thus, this work is the first one to investigate the parasitism by anisakid nematodes comparatively between young and adult specimens of S. magellanicus in southern Brazil. Parasitological indexes were compared in relation to host gender, parasite development stage and gender, and sites of infection. The gastrointestinal tract of 36 specimens of Magellanic penguins found dead along the coast of Paraná and Rio Grande do Sul states, were analyzed. The nematode fauna was composed of a single species, the anisakid, Contracaecum pelagicum. In Rio Grande do Sul, the young specimens of S. magellanicus were more intensely and abundantly parasitized by C. pelagicum than the adult ones. The stomach and the intestine were the organs that showed highest mean density of infection by adult and larval nematodes, respectively, in the hosts collected in both locations. A high prevalence was observed in both areas, although no differences in the parasitism between male and female penguins were detected. The young Magellanic penguins found in Paraná were on average less parasitized than the ones found in Rio Grande do Sul. These results, together with data available in the literature, suggest a latitudinal variation in the parasitological indexes of C. pelagicum, which are related to changes in the diet of the Magellanic penguins during their winter migration in the Southwestern Atlantic Ocean.