17. THE EFFECT OF HEAT ON DIFFERENT LIFE HISTORY STAGES OF THE ENDOPARASITIC WASP COPIDOSOMA FLORIDANUM

Abstract

Endoparasitoids are organisms that live inside of their host before killing them. Because of the close relationship shared between endoparasitoids and their hosts, the former is exposed to the stressors of their hosts’ environment. Host stressors, in turn, can affect the endoparasitoid. Several stressors exist that may affect an organism’s physiology or behavior, including starvation, infection, and heat. The effects of heat stress on organisms in general are of increasing concern because of climate change. Copidosoma floridanum is an endoparastic wasp that lays its eggs in the eggs of Trichoplusia ni, a cabbage looper. C. floridanum then develops inside the T. ni larvae, ultimately producing two larval castes, a reproductive caste and a sterile soldier caste. Previous work has shown that the number of soldier caste individuals that develop can change in response to environmental conditions. To explore how temperature affects two life history stages of C. floridanum, we allowed C. floridanum females to parasitize T. ni eggs at three different temperatures, 19º C, 27ºC, and 37ºC. The 27ºC treatment had the highest rate of parasitism. Additionally, we heat shocked T. ni larvae parasitized by C. floridanum by putting them at 42ºC for 4 hours, after which the number of soldier larvae produced were counted at different time points. Over time, there was no increase in the number of soldier larvae produced in response to heat shock. These results suggest that the degree of response to heat in C. floridanum differs across life history stages.