| Summary: | The effects of temperature on embryonic physiology have been examined in the Nauyuk and Labrador strains of Arctic char, 'Salvelinus alpinus ', using a new isolation technique for the separation of the yolk from embryonic tissue. In both strains survival rates were lower at higher incubation temperatures. Investigation into the metabolic response to different temperatures (4, 6, 8 and 10°C) has revealed thermal acclimation in O 2 consumption and cytochrome c oxidase activity since these two parameters changed with acute but not chronic temperature exposures. Arctic char embryos were found to be incapable of homeoviscous adaptation, as membrane phospholipid composition was not affected by temperature in the embryonic tissue. The concentration of free amino acids were higher in the yolk and lower in the embryonic tissue in the 10°C acclimated embryos as compared to the 4°C acclimated embryos, suggesting that free amino acid uptake may have been reduced at higher incubation temperatures. The lower survival rates observed at higher temperatures may be related, in part, to the lack of biochemical modifications observed in response to incubation temperature.
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