Helminth Parasitism in Isloated Populations of a Neotropical Forest Rodent

Rodent population - Panama;Proechimys;Parasites;Parasitism;Helminth

Ireland, Annette L.Adler, Gregory ;

University of Wisconsin

关键词: Rodent population - Panama;    Proechimys;    Parasites;    Parasitism;    Helminth;   

Others  :  https://minds.wisconsin.edu/bitstream/handle/1793/62201/Ireland%2c%20Annette.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: University of Wisconsin

【 摘 要 】

Parasitism is an extremely common life style that has evolved independentlymany times, and parasites are diverse with respect to that life style. Parasitic nematodesare commonly found in rodents and can serve as excellent model systems forunderstanding parasite-host interactions. Proechimys semispinosus (the CentralAmerican spiny rat) is a widely-distributed and common rodent in Neotropical forests.Several species of intestinal nematodes have been isolated from this rat, includingHeligmostrongylus sp. I analyzed data collected from isolated populations of P.semispinosus. The data set included counts of eggs of Heligmostrongylus sp. that wereshed in the feces of their rat hosts. The data were collected over a 13-month period(January 1997 through January 1998) from rat populations on seven small islands inGatun Lake, central Panama. Rats were censused monthly by live trapping, and monthlyfruit availability was assessed by counting the numbers of trees and lianas that wereproducing ripe fruits. Rat populations on five islands were provisioned withsupplemental food during the period of least food availability (November and December1997 and January 1998) to test the effects of host nutritional status on reproductiveactivity of Heligmostrongylus sp. Rat fecal samples were collected from each capturedindividual, and nematode eggs were counted from each sample. I estimated monthly ratdensities, fruit densities, and per capita fruit availability for each island. I also calculatedthree indices (egg density, prevalence, and egg density of egg-shedding individuals ) ofHeligmostrongylus sp. reproductive activity. Egg density and density of egg-sheddingindividuals were log10+1-transformed, and prevalence was arcsine square roottransformed.I computed cross-correlation functions of each pair-wise islandcombination to search for synchrony in nematode reproductive activity among insularpopulations of rats. I computed Spearman rank correlation coefficients of island-widemeans of the three Heligmostrongylus sp. indices and rat density, fruit density, and percapita fruit availability. I used repeated measures analysis of variance (ANOVA) tosearch for differences in mean parasite indices with respect to treatment period, treatmentgroup, population nested within treatment group, month, and the month x treatment groupinteraction. I then searched for differences in the mean number of eggs shed by ratsaccording to age and sex by constructing a full ANOVA model that included age, sex,and the interaction. I compared the proportions of male and female rats that shednematode eggs at some time in their capture histories. I used linear regression analysis tosearch for a relationship between the number of eggs shed and rat body weight.Reproductive activity of Heligmostrongylus sp. varied widely over time, but there waslittle evidence of synchrony among islands. There were no associations of the parasiteindices with rat density, fruit density, or per capita fruit availability. Food provisioninghad no effect on reproductive activity, but such activity varied among islands. There2were no differences in Heligmostrongylus sp. reproductive activity between age classesof rats, but female rats shed more eggs than did males. By contrast, the proportions ofmale and female rats shedding eggs did not differ, and there was no relationship betweenthe number of eggs shed by a rat and it body weight. Results suggest that reproductiveactivity of Heligmostrongylus sp.is infrequent and aseasonal but spatially variable. Hostnutritional status has little effect on nematode reproductive activity, but dietary orphysiological consequences of female rat reproduction may increase nematode activity. Isuggest that Heligmostrongylus sp. has little impact on host fitness or population-levelprocesses.