The role of the blood in the temperature dependence of oxidative metabolism in decapod crustaceans. II. Interspecific adaptations to latitudinal changes

Abstract

AbstractThe effects of acclimation temperature on hemocyanin‐oxygen (HcO2) transport were examined in two species of decapod crustaceans representing different geographic and thermal ranges. In the coldwater species Cancer borealis and the warmwater species Menippe mercenaria, the performance of the HcO2 transport system is maximized at 15 °C, a summer temperature in the northern habitat and a winter temperature in the southern habitat. In C. borealis little unloading at the tissues occurs at 5 °C, and in M. mercenaria oxygenation at the gill is incomplete at 25 °C. The temperature coefficients describing rates of ventilation, heartbeat, and total oxidative metabolism fall within a narrow range (Q10 = 1.9−3.6), providing no indication of ventilatory or cardiovascular adjustments that would allow the HcO2 transport system to function at the maximum level at different temperatures. Comparison of the HcO2 equilibrium properties suggests that HcO2 affinity has been selected for a particular thermal range, but not cooperativity or pH dependence. The thermal limits of the O2 transport system are set by both the direct effect of temperature on HcO2 equilibrium and the indirect effect via the Bohr shift that accompanies the change in blood pH with temperature.