THE ACTIVITIES OF ENZYMES ASSOCIATED WITH THE INTERMEDIARY AND ENERGY-METABOLISM IN HYPOGEAN AND EPIGEAN CRUSTACEANS

The activities of 18 enzymes involved in the intermediary and energy m etabolism were measured in certain widely-spread peracarid crustaceans : 3 hypogean (Niphargus virei, Niphargus rhenorhodanensis and Stenasel lus virei) and 2 epigean (Gammarus fossarum and Asellus aquaticus) one s. The activities of numerous enzymes were correlated with the known m etabolic rates of the 5 species. Such rates are reduced in hypogean or ganisms: levels of enzymatic activity in subterranean species were 1.2 to 8.6 times lower than in epigean species of the main key regulatory enzymes involved in the Krebs cycle and glycolysis (phosphofructokina se, pyruvate kinase, hexokinase and citrate synthetase). The relative activities of phosphofructokinase, glycogen phosphorylase and hexokina se clearly indicated that glycogen was the main fuel oxidized in both epigean and hypogean organisms. A higher glycogen phosphorylase/hexoki nase ratio in hypogean than in epigean crustaceans showed that subterr anean species has a greater ability to function anaerobically. The pre sence of high activities of glutamate-pyruvate transaminase and lactat e dehydrogenase in all species (and of malate dehydrogenase and fumara se in hypogean species) was indicative of a coupled fermentation of gl ycogen and glutamate during anaerobiosis, with lactate and alanine as end-products (as well as succinate in hypogean species). A low fructos e-1,6-bisphosphatase/phosphofructokinase ratio, associated with a low level of phosphoenolpyruvate carboxykinase activity, indicated that th e glycolytic pathway was active and that gluconeogenic ability was lim ited in epigean crustaceans. In contrast, in hypogean species, associa tion of a high ratio and a high level of phosphoenolpyruvate carboxyki nase activity suggested a low glycolytic activity and a high gluconeog enic ability.