The cost of walking in crabs: Aerial and aquatic oxygen consumption during activity of two species of intertidal crab

Abstract

1. 1. The amphibious inertidal crab Pachygrapsus marmoratus consumed oxygen at almost equal rates in air and sea water during activity and when inactive. The low shore Carcinus medlterraneus when active or inactive respired at between 25 and 44% of the aquatic rate in air. 2. 2. Oxygen consumption in sea water increased linearly with walking speed for both species. After a 10 min period of exercise oxygen debts of between 40 and 100% of the net oxygen consumption during exercise were accumulated and repayed within 20 min. 3. 3. Costs of locomotion in sea water were temperature independent and similar to values for walking invertebrates and vertebrates. 4. 4. The circulatory adjustment during exercise included lowering of arterial and venous pO 2, maintenance of arterial to venous difference, and an increase in stroke volume.