Meeting Abstract
75.2 Tuesday, Jan. 6 Diving and digestion – the effect of an elevated metabolic rate on submergence in an aquatic ectotherm PRATT, K L*; WILSON, R S; BLOMBERG, S P; FRANKLIN, C E; University of Queensland, Australia; University of Queensland, Australia; University of Queensland, Australia; University of Queensland, Australia k.pratt@uq.edu.au
Diving vertebrates submerge for varying durations, the extent to which is determined primarily by oxygen stores and metabolic rate (calculated aerobic dive limit). Environmental and physiological factors determine oxygen stores and metabolic rate; including temperature and aquatic PO2, the effects of which are well understood. Almost completely overlooked is digestion, a physiological process which dramatically increases metabolism particularly in infrequently feeding ectotherms (eg. snakes) and the consequences for dive duration are untested. This study aimed to determine changes in metabolic rate and dive duration in response to the combined effects of temperature and aquatic PO2 and to digestion in the fully-aquatic Arafura filesnake (Acrochordus arafurae). In the first experiment, three temperatures (20C, 26C, 32C) were used under aquatic normoxia and hypoxia. Metabolic rate increased with temperature (Q10 = 2.2) but was not affected by PO2. Snakes used aquatic respiration during normoxia but lost oxygen to the water during hypoxia, increasing aerial respiration to maintain a constant metabolic rate. As temperature increased, maximum dive time under normoxia decreased from 77 min at 20C to 28 min at 32C with hypoxia further reducing dive time to 21 min at 32C. Digestion was more energetically demanding and enduring than changes with temperature and PO2. Metabolic rate increased with meal size and digestion of the largest meal (15% body mass) resulted in an 11-fold increase in metabolic rate. Aquatic respiration increased three fold during digestion. Dive duration reduced to below 20% of fasting times (< 5 min) with the largest meal and the smallest meal (1.6%) halved maximum dive time.
