Behavioral Changes in Tribolium Beetles Infected with a Tepeworm: Variation in Effects Between Beetle Species and Among Genetic Strains

We report behavioral alterations induced by tapeworm (Hymenolepis diminuta) infection in several genetic strains of two species of flour beetles, Tribolium, under two infection levels in a laboratory environment. Under a high level of infection, Tribolium castaneum (strain cSM) shows decreased emigration and surface-seeking behavior and increased cannibalism. In contrast Tribolium confusum (strain b+) shows increased emigration and surface-seeking behavior, and cannibalism is not significantly changed. Under a low level of infection, emigration is not affected in any of the 11 genetic strains examined. Prevalence of parasitism is positively associated with emigration rate. Different genetic strains of T. confusum exhibited different susceptibility to tapeworm infection, suggesting intraspecific genetic variation in susceptibility to infection. This genetic basis may reflect past differences in selection resulting from different infection histories and suggests susceptibility to infection could evolve as a result of future selection. This variation in changes in host behavior seen among genetic strains also suggests that caution is needed before generalizing about expected changes in host behavior induced by a particular parasite and before concluding that such changes represent an adaptive manipulation of host behavior by a parasite species.