Parasites of franciscana (<i>Pontoporia blainvillei</i>) from São Paulo and Paraná States, Brazil

Abstract

The franciscana, Pontoporia blainvillei, is a threatened small cetacean of the western South Atlantic Ocean and is commonly caught incidentally in fishing nets along its distribution. Detailed studies regarding parasite loads of P. blainvillei have been recommended as a tool to evaluated ecological segregation and stock structure. We analyzed metazoan parasites from stomach, intestines and lungs of 41 franciscanas from three close geographical areas: Group 1, Guarujá and Praia Grande (São Paulo State), n=12 (24° 00'S, 46° 17'W); Group 2, Cananéia (São Paulo State), n=17 (25° 00'S, 47° 56'W); Group 3, Paraná State, n=12 (25° 30'S, 48° 23'W). The sample consists mainly of immature specimens, less than 3 years old. No parasites were found in the lungs analyzed. The acanthocephalan (Polymorphus sp.) found in two stomachs were considered occasional. The trematode Hadwenius pontoporiae (Digenea: Campulidae) was the only parasite found in the intestines with prevalence of 100%; for Group 1, 82.35%; for Group 2 and 58.33%; for Group 3. The mean intensity of H. pontoporiae for Groups 1, 2 and 3 was 39.5, 25.05 and 13.5 parasites per host, respectively. In this study there was a significant difference between the number of parasites among the three groups (Kruskal-Wallis test, p=0.012). Groups 2 and 3 are geographically close, and exhibited non-significant differences in the total number of parasites found (Mann-Whitney test, p=0.063). Groups 1 and 3, that are further apart geographically, differed significantly in the total number of parasites found (Mann-Whitney test, p=0.003). Through the analysis of data from the areas where H. pontoporiae was found [i.e. Areas 1, 2, 3 (this study), Rio Grande do Sul State and Argentina], it could be noticed that the prevalence and mean intensity increase as latitude increases. H. pontoporiae may continue to be useful as a biological tag for identifying franciscana's ecological stocks, together with information from genetic, morphometric and other biological studies. However, it is essential that standardized methodology be used in the collection of the parasite data.