AEROBIC CAPACITY OF THE BLUE-CRAB, CALLINECTES-SAPIDUS

The respiratory responses of Callinectes sapidus to enforced strenuous exercise were examined in crabs acclimated to seawater at 13-degrees-C, 20-degrees-C, and 28-degrees-C Standard and maximal O2 uptake rates (Mo2) and aerobic metabolic scope (= maximal Mo2 - standard Mo2) all increased fourfold between 13-degrees-C and 28-degrees-C Factorial aerobic scope (FAS = maximal Mo2 divided-by standard Mo2) was 4.6 at all temperatures. For such a highly active and proficient swimmer, C. sapidus displays a rather modest FAS compared with other aquatic and terrestrial decapod crustaceans. It appears that the evolution of swimming in the Portunidae did not involve modifications of the ventilatory and circulatory systems to achieve exceptional rates of O2 uptake and transport during exercise. The long-distance swimming capabilities of C. sapidus apparently result from a low aerobic cost of transport plus the capacity to sustain exercise at or near maximal Mo2, which allows this species to fully exploit its limited aerobic scope.