HELMINTH COMMUNITIES OF PONTOPORIA-BLAINVILLEI (CETACEA, PONTOPORIIDAE) IN ARGENTINEAN WATERS

We studied the helminth communities of franciscanas (Pontoporia blainv illei) to establish the relative importance of ecological and evolutio nary factors in their organization. Forty-six animals obtained from by -catch in Argentinian waters from 1988 to 1990 were surveyed. The helm inth communities were depauperate. Only five helminth species were det ected, 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 recur rent group. Contrary to the stochasticity observed in other cetacean s pecies, the helminth infracommunities were largely predictable, with l ittle change over the years. The low vagility and coastal bottom-feedi ng habits of the franciscanas may account for this. The distribution o f helminth species among their hosts was bimodal and colonization was nonrandom. This pattern might result from helminth specificity and tnh e specialized diet of the host. The depauperate condition of both the component community and infracommunities contrasts with general predic tions for large aquatic endotherms. Comparison with franciscanas from Uruguay suggests that the helminth communities are unsaturated and hav e low potential for colonization. This probably shows the influence of host evolution on the helminth component community, as previously pro posed for other cetacean species.