| Summary: | Submerged lobsters at 15°C were normoxaemic (Ca O O2 = 0.52 mmol l-1 at a Pa O O2 of 6.53 kPa) and normocapnic (Pa CO CO2 = 0.44kPa; [HCO 3 -] = 9.3mequiv l-1 and pHa = 7.78). After 3h in air the haemolymph was markedly hypoxic and hypercapnic (Pa O O2 = 1.6 kPa; Ca O O2 0.2 mmol l-1; Pa CO CO2 = 0.7kPa and pHa = 7.64). Disturbance after 3h in air caused a greater increase in Pa CO CO2 to 1.28 kPa and a fourfold increase in lactate levels to 3.6 mmol 1-1. The combined respiratory and metabolic acidosis reduced pHa to 7.39. After 14 h in air, undisturbed lobsters remained hypoxic and hypercapnic (Pa O O2 = 1.2kPa; Pa CO CO2 = 1.2kPa). Lactate levels had increased to 6.2 mmol l-1. Despite this clear limit on respiratory gas exchange in air, oxygen transport by the haemolymph was restored. A rise in buffer base ([HCO 3 -] = l5.8 mequiv l-1) compensated for the potential respiratory and metabolic acidosis and pH was unchanged at 7.63. The combined effects of the increase in lactate ( logP 50 / log[lactate] = -0.175) and calcium ( logP 50 / log[Ca2+] = -0.20 at pH7.63) levels contributed to an increase in oxygen affinity of haemocyanin at constant pH. Consequently, mean Ca O O2 increased from 0.2 to 0.38 mmol l-1 between 3h and 14h in air. Resubmergence after 14 h in air resulted in a transient alkalosis due to retention of bicarbonate; oxygen and CO 2 were rapidly restored to submerged levels. The lobster possesses the appropriate respiratory adaptations for survival during the relatively long periods of exposure in air encountered during commercial shipment.
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