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 enzym es from energy metabolism, restructuring membrane phospholipids and modulat ing membrane fluidity. Although much is known about the temperature biology of earthworms, it is not known to what extent earthworms employ compensato ry changes in enzymatic capacities and membrane physical properties after e xposure to low temperature. We examined activities of enzymes from glycolys is and central oxidative pathways as well as fluidity and phospholipid fatt y acid composition of mitochondrial membranes prepared from the body wall o f the temperate oligochaete Lumbricus terrestris after a one month acclimat ion to 5 degrees and 15 degreesC. No compensation occurs in central pathway s of oxidative metabolism since activities of cytochrome-c oxidase and citr ate synthase, when measured at a common temperature, are similar for 5 degr eesC and 15 degreesC-acclimated animals. In contrast, activity of pyruvate kinase is elevated 1.3-fold after acclimation to 5 degreesC. Mitochondrial membranes display inverse compensation with respect to temperature (membran es from 5 degreesC animals are more ordered than membranes from 15 degreesC animals). Our results, in combination with earlier reports, indicate that routine metabolism in L. terrestris may be maintained at reduced temperatur es with little or no change in enzymatic capacities and inverse compensatio n of mitochondrial membranes. (C) 2001 Elsevier Science Inc. All rights res erved.