Energetics of swimming in Callinectes sapidus and walking in Homarus americanus

Abstract

1. 1. The relationship between swimming speed and oxygen consumption was investigated in the blue crab Callinectes sapidus. 2. 2. Estimates of maximum oxygen consumption were proportional to W 0.35 whereas oxygen consumption of inactive animals was proportional to W 0.67; factorial aerobic scope (maximal rates/inactive rates) declined from 6 to 4 across the weight range of animal studied. 3. 3. At the end of swimming for 30 min oxygen consumption returned to pre-exercise levels within 20 min and the oxygen debt was 11% of the net increase in oxygen consumption during activity. 4. 4. In the lobster Homarus americanus walking speed was linearly related to oxygen consumption and factorial aerobic scope was about 4 and remained constant across a weight range. 5. 5. Oxygen debts were not detectable at the end of 30 min of walking. 6. 6. Correlated with the aerobic nature of their activity and their fatigue resistance the power stroke muscle in both species contained high numbers of mitochondria-rich slow muscle fibres. 7. 7. The minimal weight and velocity specific net costs of transport declined with increasing body size and were close to the values for swimming fish rather than those for walking crustaceans.