Aerobic and anaerobic energy expenditure during rest and activity in montane Bufo b. boreas and Rana pipiens

The relations of standard and active aerobic and anaerobic metabolism and heart rate to body temperature ( T b ) were measured in montane groups of Bufo b. boreas and Rana pipiens maintained under field conditions. These amphibians experience daily variation of T b over 30°C and 23°C, respectively (Carey, 1978). Standard and active aerobic and anaerobic metabolism, heart rate, aerobic and anaerobic scope are markedly temperature-dependent with no broad plateaus of thermal independence. Heart rate increments provide little augmentation of oxygen transport during activity; increased extraction of oxygen from the blood probably contributes importantly to oxygen supply during activity. Development of extensive aerobic capacities in Bufo may be related to aggressive behavior of males during breeding. Standard metabolic rates of both species are more thermally dependent than comparable values for lowland relatives. Thermal sensitivity of physiological functions may have distinct advantages over thermally compensated rates in the short growing season and daily thermal fluctuations of the montane environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47726/1/442_2004_Article_BF00348070.pd

The Influence of Symbiotic Dinoflagellates on Respiratory Processes in the Giant Clam Tridacna squamosa

Several aspects of respiratory gas exchange are distinctive in the giant clam Tridacna squamosa, which obtains nutrients from symbiotic dinoflagellates found in the mantle. During the day, when more oxygen is produced than consumed by the host and its symbionts, oxygen extraction is negative. Exhalant water P02 is higher than inhalant water P02, and prebranchial blood P02 is higher than heart blood P02. Ventilation of the mantle cavity and the gills continues, which rids the system of much excess oxygen and, possibly, prevents the formation of gas bubbles in the blood, which is supersaturated. In the dark, when the oxygen balance shifts to a rate of uptake that is unexceptional among lamellibranchs, the ventilation rate remains low and oxygen extraction high relative to species that rely exclusively on an exogenous food source. On a 24-hr basis, the total oxygen uptake exceeded the total oxygen production