Related changes in hemolymph acid-base status, electrolytes, and ecdysone in intermolt crayfish (Procambarus clarkii) at 23°C during extracellular acidosis induced by exposure to air, hyperoxia, or acid

The relationships between hemolymph acidic-basic equivalents (pH, PCO₂ and [HCO₃^- + CO₃^2-]), electrolytes (Na, K, Ca, Mg, and Cl), and ecdysone concentration were investigated in the crayfish Procambarus clarkii at 23°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, crayfish developed an initial (3-h) respiratory acidosis that was completely compensated within 24 h by metabolic base [HCO₃^- + CO₃^2-] 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 characterized by an initial (3-h) respiratory acidosis followed by a metabolic acidosis. The combined acidosis remained uncompensated, and circulating ecdysone decreased after 24 h. Acid exposure produced a purely metabolic acidosis that was partially corrected by a respiratory alkalosis between 48 and 72 h and was accompanied by an increase in circulating ecdysone. Ca and K decreased. Collectively, the experiments established a relationship between extracellular ecdysone and pH. Meanwhile, Ca remained relatively constant in all 3 treatments.