The energy metabolism of the leech Hirudo medicinalis in anoxia and muscular work

The medical leech Hirudo medicinalis has only small reserves of glycogen (˜ 40 μmol/g fresh weight), but malate is present in comparatively high concentrations (8 to 10 μmol/gm fresh weight) in the tissues and in the blood. Leeches are able to survive several days of anoxia at 20°C. From the onset of anoxia the level of malate drops rapidly and concomitantly the concentration of succinate rises in converse manner. After the initial phase, both metabolites do not change significantly. Then large quantities of propionate accumulate which, in part, are also excreted into the surrounding water. In contrast, continuous swimming causes the concentration of lactate to rise steeply and lactate is the dominant end product. There is only a modest decrease in the concentration of malate whereas succinate does not change. These distinct patterns of metabolite concentrations arising in anoxia and in muscular activity seem to indicate that different modes of energy metabolism are used in both situations.