RELATED CHANGES IN HEMOLYMPH ACID-BASE STATUS, ELECTROLYTES, AND ECDYSONE IN INTERMOLT CRAYFISH (PROCAMBARUS-CLARKII) AT 23-DEGREES-C DURING EXTRACELLULAR ACIDOSIS INDUCED BY EXPOSURE TO AIR, HYPEROXIA, OR ACID

The relationships between hemolymph acidic-basic equivalents (pH, PCO2 and [HCO3- + CO32-]), electrolytes (Na, K, Ca, Mg, and Cl), and ecdys one concentration were investigated in the crayfish Procambarus clarki i at 23 degrees C during extracellular acidosis resulting from: (1) 24 -h aerial exposure, (2) 96-h hyperoxic exposure (PO2 > 550 mm Hg), or (3) 96-h acid exposure (pH 4.0). A control series failed to reveal any significant effects of repetitive hemolymph sampling. In air, crayfis h developed an initial (3-h) respiratory acidosis that was completely compensated within 24 h by metabolic base [HCO3- + CO32-] accumulation . Circulating Ca and Cl both decreased at 24 h, while K increased. In this case, there was evidence that acid-base balance was corrected by ion exchange with the intracellular compartment. Hyperoxia was charact erized by an initial (3-h) respiratory acidosis followed by a metaboli c acidosis. The combined acidosis remained uncompensated, and circulat ing ecdysone decreased after 24 h. Acid exposure produced a purely met abolic acidosis that was partially corrected by a respiratory alkalosi s between 48 and 72 h and was accompanied by an increase in circulatin g ecdysone. Ca and K decreased. Collectively, the experiments establis hed a relationship between extracellular ecdysone and pH. Meanwhile, C a remained relatively constant in all 3 treatments.