Meeting Abstract
P2.107 Saturday, Jan. 5 Are ectoparasites always harmful to their hosts? DOWNS, C.J.*; ST. JULIANA, J.R.; WIELEBNOWSKI, N.; KRASNOV, B.R.; KHOKHLOVA, I.S.; Ben-Gurion Univ. of the Negev, Israel; Ben-Gurion Univ. of the Negev, Israel; Indiana State Univ., Terre Haute, Indiana; Ivy Tech Community College Wabash Valley, Terre Haute, Indiana ; Chicago Zoological Society, Brookfield Zoo, Illinois; Ben-Gurion Univ. of the Negev, Israel; Ben-Gurion Univ. of the Negev, Israel downsc@gmail.com
Parasites by definition harm their hosts, whereas hosts defend themselves against parasites. While the negative effects of endo- and micro-parasites have been repeatedly demonstrated, studies on ectoparasites often failed to reveal this. Parasites are distributed unevenly among different host species. The host species that supports majority of parasite individuals is considered as the principal host for that parasite, while other hosts are considered as auxiliary hosts. Using fleas parasitic on small mammals as a model host-parasite association, we measured the effects of 4 different fleas on fecal glucocorticoid metabolite concentrations (FGMC) of 8 different hosts. The level of FGMC among rodent species infested by the same flea increased with the phylogenetic distance of a given rodent from the principal host of a given flea species. We also compared metabolic rates of parasitized and non-parasitized hosts in 8 different flea-rodents pairs. We found that metabolic rate of the auxiliary host increased with flea infestation while no such changes were found in the principal host. This indicates that the principal host have greater tolerance for parasite than an auxiliary host. In addition, host-induced flea mortality increased with the phylogenetic distance of a given rodent from the principal host of this flea species. These results suggest that the degree of parasite-induced harm is determined by history of association of a given host and a given parasite during which a parasite may fine-tune its strategy of host exploitation not to evoke anti-parasitic defense of its host.
