The effect of acute changes in temperature and light on the aerobic metabolism of embryos and yolk-sac larvae of turbot (Scophthalmus maximus)

The effect of acute changes of temperature and light on the rates of oxygen consumption and ammonia excretion of developing embryos and yolk-sac larvae of turbot (Scophthalmus maximus) reared at 15degreesC were studied. Short-term temperature adjustments of +/-2degreesC gave a mean Q(10) of 2.6 for the rate of oxygen consumption. Neither the presence nor the absence of light significantly influenced this response to acute temperature changes, despite light causing a significantly higher rate of oxygen consumption in the yolk-sac larvae between 9 and 12 days after fertilisation. This elevated metabolic rate in the presence of light occurred after pigmentation of the eyes and was probably due to activity associated with food-searching behaviour of this visual feeder. Similarly, for most development, the presence or absence of light and acute temperature adjustments did not cause any significant shift in the relative fraction of amino acids catabolised at 15degreesC. However, on day 10 after fertilisation when peak rates of oxygen consumption occurred in the yolk-sac larvae exposed to light, the significantly elevated apparent nitrogen quotients indicated that greater amounts of amino acids were utilised for catabolic substrate oxidation.