DIETARY FATS, SELECTED BODY-TEMPERATURE AND TISSUE FATTY-ACID COMPOSITION OF AGAMID LIZARDS (AMPHIBOLURUS-NUCHALIS)

The composition of tissue and membrane fatty acids in ectothermic vert ebrates is influenced by both temperature acclimation and diets. If su ch changes in body lipid composition and thermal physiology were linke d, a diet-induced change in body lipid composition should result in a change in thermal physiology. We therefore investigated whether the se lected body temperature of the agamid lizard Amphibolarus nuchalis (bo dy mass 20 g) is influenced by the lipid composition of dietary fatty acids and whether diet-induced changes in thermal physiology are corre lated with changes in body lipid composition. The selected body temper ature in two groups of lizards was indistinguishable before dietary tr eatments. The selected body temperature in lizards after 3 weeks on a diet rich in saturated fatty acids rose by 2.1 degrees C (photophase) and 3.3 degrees C (scotophase), whereas the body temperature of lizard s on a diet rich in unsaturated fatty acids fell by 1.5 degrees C (pho tophase) and 2.0 degrees C (scotophase). Significant diet-induced diff erences were observed in the fatty acid composition of depot fat, live r and muscle. These observations suggest that dietary lipids may influ ence selection of body temperature in ectotherms via alterations of bo dy lipid composition.