The role of branchial ventilation in hemolymph acid-base changes in the shore crabCarcinus maenas during hypoxia

Abstract

1. When exposed to hypoxia in the ambient medium, the crabCarcinus maenas increased and sustained high levels of branchial ventilation for up to 70 h (Fig. 1). 2. The role of hyperventilation in establishing changes in hemolymph acid-base status during hypoxia was investigated. Hemolymph pH and\(P_{CO_2 } \) changes in hypoxic crabs (Figs. 2 and 4) were compared with crabs whose branchial chambers were artificially hyperventilated in normoxia by siphoning water through a mask attached to the carapace (Fig. 3). 3. Hyperventilation alone does not account for the observed alkalosis during hypoxia. It is suggested that changes in both CO2 production and ventilation may be responsible for altering hemolymph acid-base status. 4. Artificial hyperventilation in normoxic crabs resulted in a respiratory alkalosis which is fully compensated after 16 hours by a metabolic acidosis (Fig. 3). 5. Reduction of the hemolymph bicarbonate pool during hypoxia did not interfere with the ability of crabs acclimated to low salinity to regulate hemolymph chloride ion concentration (Fig. 5).