Comparative study on the metabolic responses of subterranean and surface-dwelling amphipods to long-term starvation and subsequent refeeding

The effects of long-term starvation and subsequent refeeding on intermediar y and energy metabolism were investigated in two subterranean aquatic crust aceans, Niphargus rhenorhodanensis and Niphargus virei, and in a morphologi cally similar surface-dwelling species, Gammarus fossarum, The metabolic re sponse to prolonged food deprivation was monophasic in G, fossarum, showing an immediate, linear and large decline in all of the energy reserves. In c ontrast, both subterranean organisms displayed successive periods of glucid ic, proteo-glucidic then lipidic-dominant catabolism during food deprivatio n, In both subterranean species, lipids (51% of the energy consumed during a 180-day starvation period) and proteins (44%) were the most metabolized s ubstrates in terms of total energy, whereas glycogen (5%) contributed littl e energy. G, fossarum displayed a different energetic strategy: proteins co mprised 56% of the energy losses during a 28-day starvation period, total l ipids some 39% and glycogen reserves only 5%, We propose an energy strategy for food-limited subterranean crustaceans involving the possession of (1) higher amounts of stored arginine phosphate, triglycerides and glycogen and (2) lower utilization rates of stored metabolites than G, fossarum and num erous other surface-dwelling crustaceans, making the fueling of food depriv ation possible for a longer time. In addition, these species had a faster a nd more efficient assimilation of available nutrients during recovery from food deprivation, enabling preparation for a new nutritional stress. These specific adaptive responses might be considered, for N, virei and N, rhenor hodanensis, as an efficient energy-saving strategy for an environment where extended starvation periods alternate with sporadic feeding events, theref ore improving their competitive advantages.