Behavioural, ventilatory and respiratory responses of epigean and hypogean crustaceans to different temperatures.

Impact of temperature (from -2 to 28 degrees C) on survival, oxygen consumption, locomotory and ventilatory activities was measured in two aquatic subterranean crustaceans (Niphargus rhenorhodanensis and Niphargus virei) and in a morphologically close surface-dwelling crustacean (Gammarus fossarum). The hypogean N. virei presented all characteristics of a stenothermal organism: it showed small thermal plasticity and optimised its performance on a narrow range of temperature. In contrast, the epigean G. fossarum and more surprisingly the hypogean N. rhenorodanensis can be both characterized as eurythermal organisms: they exhibited important survival times and conserved their performance optimum throughout a large range of temperature. Such differences of survival and performance patterns in two hypogean organisms were unexpected since they both live in very thermally buffered biotopes. Our data suggest fresh hypotheses about the role of glaciations in the history and adaptation of hypogean crustaceans.