Meeting Abstract
Parasites interact with nearly all free-living organisms and can impose substantial fitness costs on their hosts. Accordingly, parasitism is predicted to be a significant selective force shaping the evolution of host phenotypes. However, studies testing this prediction are challenged by the difficulty of both measuring selection and achieving long-term manipulations of parasites in the wild. In particular, current anti-parasite drug formulations (1) are not well characterized for the non-model host species typically used in studies of selection, (2) are not commercially available at concentrations suitable for many of these species, and (3) require short-term dosing schedules that are incompatible with long-term sampling required to measure fitness. To address these challenges, we developed a method for the long-term removal of nematode and arthropod parasites from the brown anole, Anolis sagrei, a small lizard that is ideally suited for long-term studies of natural selection. First, we confirmed that oral delivery of Ivermectin, a broad spectrum anti-nematode and anti-arthropod drug, is effective at lowering nematode burden in captive A. sagrei. Next, we adapted techniques from the drug development literature to create a biodegradable, in situ-gelling injection for the sustained release of Ivermectin. We characterized the appropriateness of this compound in vivo over a period of four months in captive anoles. Finally, we tested this technique using a mark-recapture study of drug-treated and control-injected males (n = 70) and females (n = 85) to characterize the impact of nematode parasites on survival in a wild population of Anolis sagrei. While our work was done in Anolis sagrei, these techniques are generalizable and should allow for the long-term removal of nematodes and arthropods in a variety of host species.
