Bioenergetic responses to the initiation of winter and glycerol formation in the leech Nephelopsis obscura

Abstract

Changes in glycogen, total lipid, glycerol, triacylglycerols, and active phosphorylase were examined in the freshwater leech Nephelopsis obscura during acclimation from summer (20 °C) to winter (4 °C) temperatures, during exposure to winter temperatures, and after return to summer temperatures, with oxygen maintained at saturation. Total lipids, triacylglycerols, and glycogen did not increase significantly until the temperature dropped to 7 °C, and glycerol concentrations did not increase until after exposure to 4 °C for 3 days. Thus, while decreased temperature triggered increased energy storage, glycerol synthesis required a cold stress. Shifting cold-stressed N. obscura back to 20 °C resulted in rapid resynthesis of glycogen coupled with a decrease in glycerol, but no changes in total lipid and triacylglycerols.