CHANGES IN THE HEMOLYMPH ACID-BASE STATE OF THE SHORE CRAB, CARCINUS MAENAS, EXPOSED TO SIMULATED TIDEPOOL CONDITIONS

¹ Laboratoire de Neurobiologie et Physiologie Comparées, CNRS UA 1126-Université de Bordeaux I, place du Dr-Bertrand Peyneau, 33120-Arcachon, France

High-tide and low-tide conditions were established in an artificial pool containing algae by alternately circulating seawater and leaving it stagnant for successive 6-h periods. Diurnal cyclical changes of water temperature and partial pressures of oxygen and carbon dioxide were almost the same as in natural tidepools. Hemolymph acidbase status (pH, carbon dioxide partial pressure, and bicarbonate concentration) was determined during day and night low-tide periods in crabs (Carcinus maenas) acclimated to artificial pool conditions. Except at water Po₂ below 20 Torr where the animals breathed air and developed a partially compensated respiratory acidosis, acidbase disturbances induced by changes of respiratory gases were much less than those observed in single-factor laboratory experiments, mainly because of counteracting influences of oxygen and carbon dioxide. This resulted in a decrease of hemolymph pH at increasing water temperature of –0.016 pH unit °C^-1, consistent with the imidazole alphastat hypothesis.