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Journal of Experimental Biology 144,417-436 (1989)
Published by Company of Biologists 1989

Oxygen Transport and Acid-Base Balance in the Haemolymph of the Lobster, Homarus Gammarus, During Aerial Exposure and Resubmersion

E. W. TAYLOR ¹ and N. M. WHITELEY ²

¹ School of Biological Sciences, University of Birmingham, Birmingham B15 2TT, and nstitut für Zoologie IV, University of Düsseldorf, FRG Gatty Marine Laboratory, University of St Andrews, Scotland
² School of Biological Sciences, University of Birmingham, Birmingham B15 2TT, and Institut für Zoologie IV, University of Düsseldorf, FRG Gatty Marine Laboratory, University of St Andrews, Scotland

Submerged lobsters at 15°C were normoxaemic (Ca_OO2 = 0.52 mmol l^-1 at a Pa_OO2 of 6.53 kPa) and normocapnic (Pa_COCO2 = 0.44kPa; [HCO₃^-] = 9.3mequiv l^-1 and pHa = 7.78). After 3h in air the haemolymph was markedly hypoxic and hypercapnic (Pa_OO2 = 1.6 kPa; Ca_OO2 0.2 mmol l^-1; Pa_COCO2 = 0.7kPa and pHa = 7.64). Disturbance after 3h in air caused a greater increase in Pa_COCO2 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_OO2 = 1.2kPa; Pa_COCO2 = 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 ([HCO₃^-] = 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 (logP₅₀/log[lactate] = -0.175) and calcium (logP₅₀/log[Ca²⁺] = -0.20 at pH7.63) levels contributed to an increase in oxygen affinity of haemocyanin at constant pH. Consequently, mean Ca_OO2 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 CO₂ 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.

Key words: oxygen transport, acid-base regulation, aerial exposure, crustaceans, lobster, Homarus

Accepted on February 20, 1989

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