Structure of the helminth community of the Magellanic penguin: first results from northern Argentinean coast

DÍAZ, J. I.; PAZOS, G. E.

Ushuaia, Argentina

Congreso; V International Penguin Conference; 2004

In this work we present the first results about the parasites helminth community of Spheniscus magellanicus on the Argentinean coast. From 1996 to 2001, 30 Magellanic Penguins, which were found dead, were collected (20 from Chubut province, 6 from the same area but coming from a massive mortality occurred in 2000, and 4 from Buenos Aires province). The birds were dissected and the helminthes recovered studied using conventional techniques. The prevalences (P), mean intensities (MI) and mean abundances (MA) were calculated for each parasitic species. The 100% of the hosts were parasitized. The 20 specimens from Chubut were parasitized for some of the following helminthes: Tetrabothrius lutzi (Cestoda: Tetrabothridae) (intestine, P = 80%, MI = 42, MA = 34); Cardiocephaloides sp. (Digenea: Strigeidae) (intestine, P = 55%, MI = 128, MA = 70); Cosmocephalus obvelatus (Nematoda: Acuariidae) (esophagus, P = 25%, MI = 5, MA = 1.4); Contracaecum sp. (Nematoda: Anisakidae) (adults: esophagus and stomach, P = 40%, MI = 149, MA = 60; larvae: intestine, P = 100 %, MI = 283, MA = 283) and Corynosoma sp. (Acanthocephala: Polymorphidae) (intestine, P = 55%, MI = 55, MA = 30). The 40% of the host were parasitized by different combinations of the three species. According to the relations variance-mean and Morisita Index, the distribution of the parasite species in the host population fits the Binomial Negative model. The parasitic interactions in the intestine, which were analyzed by the Fager Index, showed only a positive association between T. lutzi and Cardiocephaloides sp. (t = 2.76; p < 0.05), although the other association values were closely to the level of significance. The index of diversity of Shannon-Weaver was relatively low (ISh = 0.9) and the equitability was of an intermediate value (E = 0.56). The specimens examined from the massive mortality were parasitized for the same helminthes parasites, excepting C. obvelatus which was absent; the prevalences and intensities were much higher, indicating a bad condition of the birds. In the penguins from Buenos Aires, C. obvelatus, T lutzi and Corynosoma sp. Were not present; however, an undescribed species Tetrabothrius species was found instead. According with the analysis performed, we can conclude that the helminth community in S. magellanicus is very predictable. The low value of parasitic diversity observed is corroborating the hypothesis that a narrow trophic spectrum corresponds with few ways of incorporating parasites, because most helminthes are transmitted by food.