Effects of acclimation temperature on enzymatic capacities and mitochondrial membranes from the body wall of the earthworm Lumbricus terrestris.

Many ectotherms respond to low temperature by adjusting capacities of enzymes from energy metabolism, restructuring membrane phospholipids and modulating membrane fluidity. Although much is known about the temperature biology of earthworms, it is not known to what extent earthworms employ compensatory changes in enzymatic capacities and membrane physical properties after exposure to low temperature. We examined activities of enzymes from glycolysis and central oxidative pathways as well as fluidity and phospholipid fatty acid composition of mitochondrial membranes prepared from the body wall of the temperate oligochaete Lumbricus terrestris after a one month acclimation to 5 degrees and 15 degrees C. No compensation occurs in central pathways of oxidative metabolism since activities of cytochrome-c oxidase and citrate synthase, when measured at a common temperature, are similar for 5 degrees C and 15 degrees C-acclimated animals. In contrast, activity of pyruvate kinase is elevated 1.3-fold after acclimation to 5 degrees C. Mitochondrial membranes display inverse compensation with respect to temperature (membranes from 5 degrees C animals are more ordered than membranes from 15 degrees C animals). Our results, in combination with earlier reports, indicate that routine metabolism in L. terrestris may be maintained at reduced temperatures with little or no change in enzymatic capacities and inverse compensation of mitochondrial membranes.