Meeting Abstract

P2-87  Friday, Jan. 5 15:30 – 17:30  Temperature alters Digestive Energetics and Fuel Selection in a Lizard PLASMAN, M; MCCUE, MD*; REYNOSO, VH; TERBLANCHE, JS; CLUSELLA-TRULLAS, S; Stellenbosch University, South Africa and Universidad Autónoma de Tlaxcala, Mexico; St. Mary’s University, Texas; Universidad Nacional Autónoma de México, Mexico; Stellenbosch University, South Africa; Stellenbosch University, South Africa melissaplasman@hotmail.com

Food provides animals with energy and other resources, yet processing an ingested meal also requires energy, this is called specific dynamic action (SDA). SDA is (at least partially) fuelled by oxidation of the recently ingested nutrients. In ectotherms, environmental temperatures can affect SDA and possibly fuel selection. We examined SDA, gut passage time, assimilation efficiency, and fuel use in the lizard Agama atra digesting crickets whose body lipids or proteins were isotopically labelled with ¹³C. Lizards were tested at three ecologically relevant temperatures (20, 25, and 32ºC). We found that at higher temperatures the magnitude of the peak in a postprandial metabolic rate increased, while duration of the SDA response and gut passage time decreased. The oxidation of dietary protein peaked earlier than that of lipids at all temperatures tested. After the peak, protein oxidation rapidly decreased. Lipid oxidation, however, remained relatively high and stable for the duration of the trial at 20 and 25ºC and only decreased, but slowly, at 32ºC trials. These results indicate that in this lizard temperature has a pronounced effect on digestive energetics and that this effect differs between nutrient classes. Changes in environmental temperatures may thus alter the energy budget and nutrient reserves of these animals.