EFFECTS OF TEMPERATURE ON CUTICULAR LIPIDS AND WATER-BALANCE IN A DESERT DROSOPHILA - IS THERMAL-ACCLIMATION BENEFICIAL

The desert fruit fly Drosophila mojavensis experiences environmental c onditions of high temperature and low humidity, To understand the phys iological mechanisms allowing these small insects to survive in such s tressful conditions, we studied the effects of thermal acclimation on cuticular lipids and rates of water loss of adult D. mojavensis. Mean hydrocarbon chain length increased at higher temperatures, but cuticul ar lipid melting temperature (T-m) did not, Lipid quantity doubled in the first 14 days of adult life, but was unaffected by acclimation tem perature. Despite these changes in cuticular properties, organismal ra tes of water loss were unaffected by either acclimation temperature or age, Owing to the smaller body size of warm-acclimated flies, D. moja vensis reared for 14 days at 33 degrees C lost water more rapidly on a mass-specific basis than flies acclimated to 25 degrees C or 17 degre es C. Thus, apparently adaptive changes in cuticular lipids do not nec essarily result in reduced rates of water loss, Avoidance of high temp eratures and desiccating conditions is more likely to contribute to su rvival in nature than changes in water balance mediated by surface lip ids.