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Host age is one of the keyfactors in host–parasite relationships as it possibly affects infestationlevels, parasite-induced mortality of a host, and parasite distribution amonghost individuals. We tested two alternative hypotheses about infestationpattern and survival under parasitism in relation to host age. The first hypothesisassumes that parasites are recruited faster than they die and, thus, suggeststhat adult hosts will show higher infestation levels than juveniles because theformer have more time to accumulate parasites. The second hypothesis assumesthat parasites die faster than they are recruited and, thus, suggests thatadults will show lower infestation levels because of acquired immune responseand/or the mortality of heavily infested juveniles and, thus, selection forless infested adults. As the negative effects of parasites on host are oftenintensity-dependent, we expected that the age-related differences ininfestation may be translated to lower or higher survival under parasitism ofadults, in the cases of the first and the second hypotheses, respectively. Wemanipulated ectoparasite numbers using insecticide and assessed the infestationpattern in adult and juvenile gerbils (Gerbillus andersoni) in the Negev Desert.We found only a partial support for age-dependent parasitism. No age-relateddifferences in infestation and distribution among host individuals were foundafter adjusting the ectoparasite numbers to the host’s surface area. However,age-related differences in survival under parasitism were revealed. Thesurvival probability of parasitized juveniles decreased in about 48% comparedto unparasitized hosts while the survival probability of adults was notaffected by ectoparasites. Our results suggest that the effect of host age onhost–parasite dynamics may not explicitly be determined by age-dependentdifferences in ectoparasite recruitment or mortality processes but may also beaffected by other host-related and parasite-related traits |
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