Biochemical acclimation of metabolic enzymes in response to lowered temperature in tadpoles of Limnodynastes peronii.

We measured the rate at which the metabolic enzymes lactate dehydrogenase (LDH), citrate synthase (CS), and cytochrome c oxidase (CCO) acclimate in the response to lowered temperature in the axial muscle of tadpoles of Limnodynastes peronii (Anura: Myobatrachidae) over 6 weeks. In addition, we measured growth rates of the tadpoles kept at both temperatures and examined the activities of these enzymes in the liver tissue of the control group and cold-acclimated group at the end of the experiment. We found that LDH acclimates in axial muscle; the differences between the control and cold-acclimated group became apparent after 21 days. After 42 days, the activity of LDH in axial muscle in the cold-acclimated group was 30% greater than the control group. Growth rates were maintained at 0.7 mm/week within both treatments despite the 10 degrees C difference in temperature between experimental groups. Both LDH and CS were increased in activity in the liver (5 and 1.3 times greater, respectively, in the cold-acclimated group). The thermal sensitivity (Q(10)) of LDH was between 20 and 30 degrees C in the cold-acclimated group (1.2+/-0.01) when compared to the control group (1.6+/-0.15). The rate at which acclimation in this species occurs is appropriate for seasonal changes in temperature, and these animals may not be able to respond to a rapid drop in temperature.