Comparative responses to severe hypoxia and subsequent recovery in closelyrelated amphipod populations (Gammarus minus) from cave and surface habitats

The locomotory and ventilatory activities, oxygen consumption, and the inte rmediary and energy metabolism modifications of a spring and a cave populat ion of the aquatic amphipod crustacean Gammarus minus were investigated in normoxia, severe hypoxia (P-O2 < 0.03 kPa) and subsequent recovery. The aim s of this study were to compare (1) the reactions of both populations to th ese experimental conditions, (2) these results with those obtained on the h ypogean amphipod Niphargus, and (3) the degree of adaptation to hypoxia sho wed by both populations of G. minus. Despite their different origins, both populations of G. minus presented identical responses in all experimental c onditions. The lethal time for 50% of the population was about 6 h, and the oxygen consumption about 44 mu mol O-2/g dw per h in normoxic conditions. The metabolic effects of severe hypoxia and subsequent recovery were signif icant compared to normoxic conditions, but also similar between both popula tions for alanine, arginine phosphate, ATP, glycogen and lactate levels. Th is study (i) underlines the statement that a high resistance to lack of oxy gen is not universally found in subterranean organisms, but is more related to oxygen availability and/or to the energetic state of each subterranean ecosystem, and (ii) highlight the diversity of adaptive responses to an env ironmental constraint expressed by hypogean crustaceans.