Abstract
Various factors influence the transmission of the tapeworm, Hymenolepis diminuta to its grain beetle host, Tenebrio molitor. Previous studies suggest the presence of a beetle attractant present in rat feces containing tapeworm eggs, which increases the probability of tapeworm transmission to the beetle. The results also suggest that various factors work to influence beetle foraging behavior. When infected beetles increase their feeding activity, they increase the probability of becoming re-infected. To simulate conditions in which host resources are limited, male and female beetles were starved, and the weight change and frass production were compared between infected and control beetles. A second experiment provided male and female beetles with food so that the beetleℓ s weight change, frass production, and food intake were compared between infected and control beetles. Results show that host resources do not limit parasite growth, and infected beetles do not feed more than uninfected beetles. Instead, male beetles feed more than females suggesting an explanation behind the higher median load of parasites recovered from male beetles. The preference of individual male and female beetles was tested for infective versus uninfective feces under varying conditions. When allowed to feed, females preferred infective feces while males showed lower activity levels. Further, the results suggest that the beetle attractant is found in infective feces instead of the tapeworm eggs. Infected hosts often behave differently from uninfected hosts. The preference of infected male and female beetles for infective bait was tested. When allowed to feed, neither male nor female beetles exhibited a preference for infective bait. This was true when beetles were tested individually or in groups. These results suggest that beetles, once infected, lose their preference for infective feces. This preference change may be a host response, parasite adaptation, or both. The preference of groups of uninfected male and female beetles was tested for infective bait. Males avoided infective feces while females showed no preference. These results suggest that the selective pressure to avoid parasitism is stronger in males than in females, which may reflect the higher reproductive cost of infection for males.