Helminth communities of Pontoporia blainvillei (Cetacea: Pontoporiidae) in Argentinian waters

Abstract

We studied the helminth communities of franciscanas (Pontoporia blainvillei) to establish the relative importance of ecological and evolutionary factors in their organization. Forty-six animals obtained from by-catch in Argentinian waters from 1988 to 1990 were surveyed. The helminth communities were depauperate. Only five helminth species were detected, two of them (Hadwenius pontoporiae and Polymorphus (Polymorphus) cetaceum) accounting for about 99% of all specimens. Three species (H. pontoporiae, P. (P.) cetaceum, and Anisakis simplex) formed a recurrent group. Contrary to the stochasticity observed in other cetacean species, the helminth infracommunities were largely predictable, with little change over the years. The low vagility and coastal bottom-feeding habits of the franciscanas may account for this. The distribution of helminth species among their hosts was bimodal and colonization was nonrandom. This pattern might result from helminth specificity and tnhe specialized diet of the host. The depauperate condition of both the component community and infracommunities contrasts with general predictions for large aquatic endotherms. Comparison with franciscanas from Uruguay suggests that the helminth communities are unsaturated and have low potential for colonization. This probably shows the influence of host evolution on the helminth component community, as previously proposed for other cetacean species.