Respiratory metabolism in pacifastacus leniusculus (Dana) (crustacea: decapoda) as related to its ecology

Summary Respiratory metabolism in the high-altitude crayfish, Pacifastacus leniusculus from Lake Tahoe (California-Nevada, U.S.A.) was investigated in a series of laboratory experiments. In general, oxygen consumption was found to be directly proportional to size when expressed per individual, and inversely proportional to size when expressed per ash-free gram dry weight per unit time. No significant variations in respiratory rates were observed between males and females. There was little variation in uptake over a temperature range of 5°C to 12.5°C, while the lowest and highest uptake values were observed at 0°C and 15°C respectively. An increase in temperature above 15°C, however, resulted in a decrease in respiratory activity. These results closely correlate with patterns of ventilatory activity, oxygen extraction efficiency, and seasonal feeding and reproductive activity in Pacifastacus as related to the annual temperature profile for their Lake Tahoe habitat. These results, as well as the extremely low tolerance of this species for low oxygen levels, suggest temperature as the possible critical environmental factor in the determination of the nature of seasonal metabolic cycles. It is concluded that Pacifastacus shows little tolerance for fluctuations in environmental oxygen and temperature and is well adapted to the narrow range of condition present in its Lake Tahoe habitat.