Marine mammal parasite relations in the patagonian ecosystem

B. BERÓN-VERA, E.A. CRESPO, M. KOEN-ALONSO, J.A. RAGA, N.A. GARCÍA

Selva Negra, Alemania

Congreso; BLACK FOREST SYMPOSIUM ON ECOLOGICAL & ENVIRONMENTAL PARASITOLOGY: THE IMPACT OF GLOBAL CHANGE; 2005

Prey-predator interactions and host-parasite specificity determine parasite communities. In the southwestern Atlantic Ocean (Patagonia, Argentina), parasites of marine mammals are being intensely studied lately. At the same time, efforts have been done to enlarge the knowledge on population dynamics and relations of these top predators, their prey and parasites, which are transmitted through the food web. Within this framework, in this work our goal was to determine the parasites of marine mammals of Patagonia and the potential parasite relations between them and their prey, whose parasites are also scarcely known. We provide a potential division of the environment, considering the habitats exploited, diet and parasites of marine mammals and, whenever possible, parasites of prey. These hosts are protected by law and no intentional killing is allowed so all the studies describe helminth communities of hosts recovered either as bay-catch or stranded on beaches. The present panorama of the southwestern Atlantic ecosystem, from the parasite-relations point of view, is as follows. Commerson´s (C. commersonii) and dusky dolphins (L. obscurus) exploit the pelagic environment and are both parasitized by Anisakis simplex, Braunina cordiformis and Pholeter gastrophilus and both prey on Engraulis anchoita, Merluccius hubbsi, Illex argentinus and Loligo gahi. E. anchoita, M. hubbsi and I.  argentinus  are intermediate hosts of A. simplex and Contracaecum sp.  The intermediate hosts and larvae of marine mammal digeneans remain unknown. Commerson´s dolphins are also exclusive hosts of Hadwenius sp1 while Hadwenius sp2 is common between dusky and hourglass dolphins (L. cruciger) from the same environment. These two hosts also shared prey items. Common dolphins (D. delphis) are also present here but their distribution range extends northward. They are parasitized by the common species to Commerson´s and duskies and, also, by Oschmarinella rochebruni, only shared with hourglass dolphins. Common dolphins, on the other hand, share Corynosomacetaceum with franciscanas (P. blainvillei) as well as their prey E. anchoita and L. sanpaulensis. Cynoscion striatus has been recently described as an intermediate host of C. cetaceum (J.T. Timi, pers. Comm.) and was an important prey of common dolphins. Although pelagic but with a more coastal distribution, bottlenose dolphins (T. truncatus) share Pseudoterranova sp. and C. australe with South American sea lions (O. flavescens) and South American fur seals (A. australis). All the pinnipeds were parasitized by Contracaecum ogmorhini and C. australe and exploit a demersal-pelagic environment where E. anchoita, M. hubbsi and E. megalocyathus are the most important prey. E. anchoita and Raneya brasiliensis are intermediate hosts of C.  australe. O. flavescens is also infected by Diphyllobothrium sp. Also coastal are Burmeister´s (P. spinipinnis) and spectacled porpoises (P. dioptrica). The former shares C. cetaceum with common and franciscana dolphins and P. gastrophilus with all the pelagic hosts. The latter is parasitized by C. australe and Phyllobothrium delphini, which is present in cetaceans of the oceanic environment beyond the Argentine shelf: sperm whales (P. macrocephalus), Gray´s beaked whales (M.grayi), Risso´s dolphins (G. griseus) and long-finned pilot whales (G. melas). The sperm whale was also infected by A. physeteris and C. bullosum. The most important prey in this environment are the squids Kondakovia longimana, Mesonichotheutis hamiltoni, Megalochranchia sp., an intermediate host of Anisakis sp. M. grayi is the only host of Scolex pleuronectis, whose intermediate hosts in the adjacent area is I. Argentinus, although among its prey are Mastigoteuthis sp., Teuthowenia sp. and Histioteuthismacrohista. Some diet information is also available for prey of these marine mammals. This study enlarges the scarce parasitological information for cetaceans of Argentina. Detailed information on parasites of marine mammals off Patagonia is relevant for a better knowledge of these top predators and their role in the food web of this little explored marine ecosystem.