Aquatic and aerial respiration in the shore crab,Carcinus maenas (L.), acclimated to 15�C

Abstract

1. Oxygen consumption\((\dot V_{O_2 } )\) and heart rate of crabs acclimated to 15°C and exposed to water or air for 3 h were not significantly different (Fig. 1). 2. When in air crabs ventilate their branchial chambers in both the forward and reversed direction (Fig. 3). 3. Exposure to air caused a marked reduction in oxygen tension of the postbranchial haemolymph\((Pa_{O_2 } )\) and a fall in pHa associated with an increase in\(Pa_{CO_2 }\). Oxygen content\((Ca_{O_2 } )\) and the\(a - v_{O_2 }\) content difference were maintained relatively high due to the oxygen binding characteristics of the haemocyanin (Table 1 and Fig. 4). 4. The concentration of lactic acid in the haemolymph was not affected by exposure to air (Table 1). 5. Exposure to air for 3 h was associated with a small reduction in total mass caused by evaporative water loss with a concomitant increase in haemolymph sodium concentration (Table 1). 6. The gill lamellae are relatively well spaced out and derive physical support from their covering of chitin. They may, therefore, be suited structurally for respiratory gas exchange in both water and air (Fig. 5).