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Journal of Experimental Biology, Vol 181, Issue 1 295-311, Copyright © 1993 by Company of Biologists

JOURNAL ARTICLES

THE EFFECTS OF SEASONAL VARIATIONS IN TEMPERATURE ON EXTRACELLULAR ACID-BASE STATUS IN A WILD POPULATION OF THE CRAYFISH AUSTROPOTAMOBIUS PALLIPES

N. M. Whiteley and E. W. Taylor

Between February 1990 and February 1991, a wild population of Austropotamobius pallipes (L.) inhabiting a large, shallow, freshwater pool in Staffordshire, central England, experienced environmental fluctuations in water temperature (1-21°C) and pH (8.2-9.5). Moulting was seasonal, with crayfish entering pre- and postmoult between May and August. Haemolymph pHa levels declined in the spring when temperatures increased from 8 to 18°C (deltapH/deltat=-0.013 pH units°C-1). This decrease was accompanied by a fall in [HCO3-] (of 4.12 mmol l-1) and [lactate] (of 4.71 mmol l-1) and a premoult elevation in PCO2 to 0.59 kPa. After ecdysis, when water temperatures and pH were at their maxima, pHa levels increased, they continued to increase as temperature fell in late summer, reaching 7.97 in intermoult crayfish at 13°C during September. This increase was accompanied by a decrease in PCO2 to 0.22 kPa at constant [HCO3-] (5-6 mmol l-1). Between September (13°C) and October (11°C) pHa fell to 7.87 with an elevation in PCO2 (of 0.18 kPa) and [lactate] (of 1.84 mmol l-1). As temperature continued to decrease (11-1°C), pHa remained unchanged despite an elevation in [HCO3-] by 2.4 mmol l-1 at constant PCO2. A mechanism accounting for the unvarying haemolymph pH values at low temperatures is proposed, stressing the importance of temperature-related seasonal changes in CO2 solubility and measured values for pK1' in addition to adjustments in [HCO3-] and PCO2. These were apparently unaffected by changes in collecting and holding protocols.




© The Company of Biologists Ltd 1993