Ventilation in the shore crab Carcinus maenas (L.) as a function of ambient oxygen and carbon dioxide: Field and laboratory studies

Ventilatory responses of crabs Carcinus maenas (L.) to changes in ambient oxygen and carbon dioxide were studied in field and laboratory experiments, over a range of Pw_O2 and Pw_co2 conditions encompassing natural variations observed in intertidal rock-pools. Ventilatory activity was assessed by recording gill chamber hydrostatic pressure and estimating the specific ventilation, Vw/M_O2, the reciprocal of the difference of oxygen concentrations in inspired and expired waters.

Variations in ambient oxygenation always induced large changes of ventilatory activity, hyperventilation in hypoxia, hypoventilation in hyperoxia. Conversely, Pw_CO2 changes either at constant P_O2 or in combination with different P_O2 values (hypoxic hypercapnia or hyperoxic hypocapnia) led only to small or even non-significant ventilatory responses. In the field, strong hyperventilation developed during tidal exposure at night, when the pool water became hypoxic and hypercapnic, whereas during the day the animals hypoventilated in progressively more hyperoxic and hypocapnic conditions.

Thus, in a typical intertidal animal such as C. maenas, the only ventilatory stimulus of ecological significance appears to be the ambient water oxygenation.