Temperature and blood acid-base status in the blue crab, Callinectes sapidus

The blood acid-base status of blue crabs. Callinectes sapidus, was assessed at temperatures ranging from 10 to 30 degrees C. Blood pH varied inversely with temperature, with a slope (dpH/tT) of - 0.012. The PaCO rose only slightly between 10 and 27 degrees C, from 2.09 torr to 2.91 torr, with the result that the total dissolved CO2 actually fell slightly due to the decrease in solubility. In vitro the blood behaved like a conventional Rosenthal system, with a rise in PCO2 at constant CT which was much greater than the observed in vivo increase. I vivo the CT of the blood decreased significantly in order to maintain the OH/H ratio. The ratio of ventilation to oxygen consumption (and presumably carbon dioxide production) was not significantly different at 10 and 27 degrees C, indicating that ventilation is not participating in the acid-base adjustment to temperature. The principal acid-base regulating mechanisms in the crab are probably ionic exchanges in the gills rather than ventilatory control of PaCO2.