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Journal of Experimental Biology 144,155-169 (1989)
Published by Company of Biologists 1989

Effects of Temperature on Gas Exchange and Acid-Base Balance in the Sea Turtle Caretta Caretta at Rest and During Routine Activity

PETER L. LUTZ ¹, ANN BERGEY ², and MICHAEL BERGEY ²

¹ Rosenstiel School of Marine and Atmospheric Science, Division of Biology and Living Resources ,4600 Rickenbacker Causeway, Miami, FL 33149, USA
² Rosenstiel School of Marine and Atmospheric Science, Division of Biology and Living Resources,4600 Rickenbacker Causeway, Miami, FL 33149, USA

Oxygen consumption, lung ventilation, plasma ion concentrations and osmolality, venous blood acid-base status and gas tensions were measured in unrestrained loggerhead sea turtles in sea water at 10, 15, 20 and 30°C at rest and during routine activity. Moderate activity caused a threefold increase in oxygen consumption, accommodated by a twofold increase in ventilation (the result of increases in breathing frequency) and a 60% increase in lung oxygen extraction. There was an increase in oxygen consumption with temperature (Q₁₀ = 2.4) alsodue primarily to an increase in oxygen extraction (decline in air convection requirement, ACR) since neither the tidal volume nor the breathing frequency changed.

Over the temperature range 15-30°C venous blood pH decreased by 0.017 units°C^-1, indicating that the maintenance of constant relative alkalinity is not confined to species of low aerobic scope. Venous blood P_COCO2 and P_OO2 increased with temperature. However, [HCO₃^-] decreased, suggesting that ventilatory adjustments alone are insufficient for regulating the thermally dependent shifts in blood pH. Plasma [K⁺] increased with temperature, which may be related to cellular-mediated adjustments in blood pH.

Temperature-related adjustments of blood pH in the loggerhead appear to be managed both at the lung (ACR-driven changes in blood P_COCO2) and tissue (ion exchange) levels. This mixed regulation is associated with the unique mode of respiration of the sea turtle.

Key words: sea turtle, temperature, oxygen consumption, lung ventilation, pH, blood gases, blood ions, lactate, urea

Accepted on March 13, 1989

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