Effects of the Naturally Occurring Parasitic NematodeChondronema passaliLeidy on Lifting Strength and Captivity-Related Body Mass Patterns in the Horned Passalus Beetle,Odontotaenius disjunctus(Illiger) (Coleoptera: Passalidae)

Abstract

Abstract Parasites are ubiquitous among insects and well-studied, but knowledge of their full range of host effects is not complete, especially concerning their impact on physical performance of hosts. The horned passalus beetle, Odontotaenius disjunctus (Illiger), in the USA is frequently parasitized by Chondronema passali Leidy, a nematode that can number in the thousands within the hemocoel. We performed an experiment that examined the effects of this parasite on a key performance metric, lifting strength, which should be important during fighting. We assessed beetle lifting strength using a vertically-mounted force gauge, as well as their body mass. At the end of the experiment, we dissected the beetles to determine parasite status and gender. The average beetle (1–2 g each) lifted between 300 and 400 g during the trials. Though the final sample size of non-parasitized beetles was small (n = 8), our results showed parasitized beetles tended to lift 17% less weight than non-parasitized beetles, and thi...