Biochemical adaptation to rapid temperature changes in scombrid red blood cell enzymes

The physiological adaptations of skipjack tuna lead to 10 degrees C changes in blood temperature every few seconds. The change in reaction rate of red blood cell LDH, MDH and GAPD to change in temperature are large under saturating substrate conditions but under intra-cellular substrate conditions reaction rate is almost independent of temperature. It seems likely that the biochemical effects observed are mediated through changes in Km with temperature. Three species related to the skipjack, but lacking its extreme physiological adaptations, had many of the biochemical adaptations seen in the skipjack. The primitive ancestor of the skipjack probably had the biochemical preadaptations needed to allow the physiological evolution seen in this lineage.