Interação parasita-hospedeiro em pequenos mamíferos da fazenda experimental do Glória: padrões interespecíficos e impactos da interação sobre os indivíduos parasitados

Abstract

The existing variation in parasites species richness and abundance among host species has become the aim of several ecological researches. Among the main factors considered responsible for the variation in parameters related to the parasites population and community are the host’s ecological characteristics, such as population density, body size and mass, longevity and reproduction. It’s of summary importance the comprehension of factors responsible for parasite abundance and species richness, because the impacts promoted by parasites might be influenced by the number of parasites occurring in a host species. In this way, the present study has two main objectives. The first one is to analyze the variation in endoparasite abundance and species richness among different rodents and marsupials species, and test the hypotheses that the host species with higher values of body weight should have the highest parasitism rates. The second objective of this research is to evaluate the impacts promoted by endoparasites on hosts, through the test of the hypotheses that the hosts with richer parasites communities and with high abundance must have decreased body condition and reduced investment in secondary sexual characters. All animals were captured in a forest fragment located at Uberlândia municipality (MG), through 12 monthly captures events of four consecutive nights between June 2011 to May 2012. 709 animals were captured through an effort of 3840 traps/night. The rodents species were represented by Rhipidomys sp. (54), Oligoryzomys sp. (24) and Hylaeamys megacephalus (16) and the marsupials species by Didelphis albiventris (10) and Gracilinanus agilis (27). The results indicates that host body mass differ between species and, co-variance tests show that abundance of endoparasites varies among rodents hosts, independent of body weight, but not among marsupials hosts. On the other hand, the richness of endoparasites is significantly different only between marsupials. These results suggest that other factors might be responsible for the variation in endoparasite abundance in rodents, such as hosts’ population density. Parasites species richness appears to be influenced by body weight, only when this variation has a large magnitude, as in the case of marsupials. Furthermore, future research must focus in others factors that could explain the variation in parasite species richness between the hosts, such as longevity. The absence of significant results on the impacts of parasitism on rodents hosts suggest some kind of overcompensation of the potential damage caused by parasites through increased food ingestion or maybe because of the lack of effects of this parasitism on these hosts species. Among marsupials, the members of G. agilis species presented positive correlation between abundance of endoparasite eggs and body condition. These results indicate that parasites might choose for hosts with greater energetic reserves, yet future tests must evaluate these hypotheses. The results observed in the impacts on reproductive investment on G. agilis and D. albiventris were conflicting. It’s possible that differences on the response of hosts to different parasites are related to pathogenicity and the latter life span.