Meeting Abstract
24.4 Friday, Jan. 4 Predigestive costs in Python regius WAAS, S.; WERNER, R.A.; STARCK, J.M.*; University of Munich (LMU), Munich, Germany; ETH Zuerich, Switzerland; University of Munich (LMU), Munich, Germany starck@uni-muenchen.de
Digestion of a meal and absorption of nutrients incur energetic costs to any organism by activating gastric functions, intestinal enzyme activity, and membrane transporters for the absorption of nutrients. Predigestive costs are supposedly high in sit-and-wait foraging snakes which tolerate long fasting periods during which functions of their GI-tract are down-regulated. Immediately after feeding, the GI-tract is activated and a 5-10fold increase of metabolic rate above SMR is observed (specific dynamic action, SDA). We studied the sources of fuel use during SDA in ball python (N = 11, avg. body mass 867 g) and quantified the predigestive energy investment. To differentiate between the snakes� own energy sources and the meal, we enriched mice with 13C by raising them on a corn diet. After feeding mice (avg. 657 kJ per meal), switching from metabolizing �own� sources to �meal� should result in less negative δ13C values of the snakes� exhaled breath. We used the time of switching and the rate of change in isotope signature to estimate the amount of energy contributed to SDA from different sources. For 3h before and 48h after feeding we measured the O2-consumption (VO2) of N=7 snakes and collected breath samples in 30-minute intervals (fasting snakes N=4 as control). VO2 during SMR was 0.03 � 0.01 ml O2 g-1 h-1. 20.5h after feeding, VO2 peaked at 0.11 � 0.03 ml O2 g-1 h-1. Total energy consumption during SDA was 63.8 kJ per snake. 2.5 h after feeding, δ13C of the exhaled breath begun changing to less negative values, indicating the beginning of metabolization of prey, reaching its least negative value at 42h, then indicating full metabolization of the prey. The total amount of energy invested from own resources was c. 10% of SDA but only 1.3 % of the cross energy intake by the prey.
