Parasitoid-induced behavioral alterations of Aedes aegypti mosquito larvae infected with mermithid nematodes (Nematoda: Mermithidae)

Parasite-induced behaviors occurring in hosts are ubiquitous and parasitized insects are amenable to the study of such changes. The majority of studies have focused on parasites with complex lifecycles and the adaptive nature of parasite-induced behaviors. Behavioral changes caused by parasitoids, multi-cellular single-host parasites that kill their host upon emergence, are far less studied and the adaptive nature of these changes is likely to be different. I conducted several experiments in which I determined that the mermithid nematode, Romanomermis culicivorax, alters larval behavior of Aedes aegypti mosquito larvae in ways that increase mosquito larval activity early in mermithid development and decrease it later in development. I also found that infected mosquito larvae behaved similarly to uninfected-starved mosquito larvae. Altered activity of infected Ae. aegypti at specific stages in parasitoid development indicate that these behavioral alterations may be parasitoid adaptations that reduce host predation risk and thus increase host and parasitoid survival. However, without definitive evidence of increased fitness, it is difficult to determine if the behavioral changes are parasitoid-adaptations or consequences of impaired nutrition due to infection. My second set of experiments addressed the adaptive nature of these behaviors: do mermithid-induced behavioral alterations increase mermithid fitness by reducing host predation risk? I compared the behaviors of infected and uninfected Ae. aegypti in the presence of the predatory mosquito larva, Toxorhynchites rutilus, and found that the behaviors of infected and uninfected larvae did not differ. In addition, when I conducted an experiment on prey choice of Tx. rutilus, there was no difference in predation rate on infected or uninfected Ae. aegypti. Based on these results, I found no evidence that mermithid-induced behavioral alterations are adaptive in ways that benefit the parasitoid by decreasing host predation risk.; Eventually, the study of parasite-induced behavioral changes of mosquito larval behavior and the impact these changes could have on trophic interactions could lead to determining possible mechanisms for how parasite-induced behavioral alterations shape community structure. I reviewed literature that addresses the ecology and parasites of container dwelling mosquitoes and the potential effect that these parasites may have on the structure of natural container communities.