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.

Helminths of the marine tucuxi, Sotalia fluviatilis (Gervais, 1853) (Cetacea: Delphinidae), in northern Rio de Janeiro State, Brazil

“…The narrow range of preferred prey in its diet could be the factor determining the low diversity of parasite groups. The same pattern was recorded for Commerson's dolphin (Cephalorhynchus commersonii) and franciscana (Pontoporia blainvillei) in Argentinian waters (Aznar et al, 1994;Berón-Vera et al, 2001). The absence of significant differences between sex, maturity and seasons was consistent with recent findings in diet studies.…”

“…Rohde et al (1995), describing the parasitism of marine fish, found trematodes in the Atlantic cutlassfish, indicating its potential to be intermediate host of these parasites. Low diversity in parasite species is related to host diet (Aznar et al, 1994). Only four parasite species were recorded in the marine tucuxi along the study area.…”

GASTROINTESTINAL HELMINTHS OF THE DUSKY DOLPHIN, LAGENORHYNCHUS OBSCURUS (GRAY, 1828), OFF PATAGONIA, IN THE SOUTHWESTERN ATLANTIC

“…The presence of acanthocephalans in the intestines of many cetaceans and pinnipeds is well documented (Raga 1992(Raga , 1994), but only three acanthocephalan species (Corynosoma hamanni, Polymorphus arctocephali, and €? cetaceum) are known to have colonized the stomachs of marine mammals (Zdzitowiecki 1984, Smales 1986, Aznar et al 1994). In the Argentine dusky dolphins, only two immature individuals of C. aastrale were found in the stomach of one animal.…”

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

“…P. blainvillei and S. guianensis are not phylogenetic closely related, which may explain in part why their parasite community is different, even though they occur in the same habitat. Aznar et al (1994) mention that Pontoporiidae dolphins have adapted secondarily to freshwater habitats at least three times, and that franciscanas may have had one or several freshwater ancestors, which would involve remarkable habitat shifts for its helminth parasites. Evolutionary restrictions may be responsible for the relatively low richness and diversity of helminths found in the franciscana.…”