Meeting Abstract
64.5 Tuesday, Jan. 6 Hyperoxia reduces the costs of digestion in snakes: Investigating the energetic consequences of the paleoatmosphere MCCUE, M.D.; Blaustein Institutes for Desert Research, Ben Gurion University mmccue@bgu.ac.il
Oxygen levels in the Earths atmosphere have fluctuated dramatically during the Phranerozoic eon, and may have reached concentrations at 60% greater than current levels. These atmospheric changes have engendered much speculation about the relationship between O2 availability and major evolutionary events among animals (e.g. insect gigantism, flapping flight, endothermy, etc.). With the exception of studies on exercising humans, a limited number of investigations have examined the effects that hyperoxic conditions can have on physiological performance variables. Given that energetic costs of maintenance and digestion can account for a majority of the total energy budget of snakes, this study was conducted to determine the effect of simulated paleoatmospheric O2 levels on the metabolic requirements (i.e. VO2 and VCO2) of postabsorptive and postprandial snakes. A series of three repeated measures experiments conducted on western diamondback rattlesnakes, (Crotalus atrox, (n = 20) under O2 concentrations ranging from 21% to 50% demonstrated that hyperoxia did not influence resting metabolic rates, but that 35% O2 was sufficient to reduce metabolic costs of digestion (i.e. specific dynamic action; SDA) by an average of 11%. It is impossible to determine whether or not extinct snakes would have shown similar responses, and to quantify the precise evolutionary significance of such responses. However, given our current understanding about the degree to which extent extant snakes are energy limited, such an energetic benefit could have had enormous implications to the life histories and feeding behaviors of ancient snakes as they radiated from their lizard ancestors.
