The effects of long-term fasting and subsequent refeeding on digestive physiology and energy metabolism

of fasting are experienced by numerous subterranean (i.e. hypogean) aquatic organisms, as many groundwater ecosystems are characterized yearly by severely limited food supplies due to lack of autotrophic production and sporadic allochthonous input (Poulson, 1964; Hüppop, 1985; Hervant et al., 1997). Even in highly productive hypogean biotopes, food resources may be extremely patchy (Malard and Hervant, 1999). In addition, many hypogean aquatic species have to cope with periods of prolonged hypoxia (Hervant et al., 1996; Malard and Hervant, 1999). An organism’s ability to withstand and recover from long periods of food shortage is a critical adaptation for survival in harsh, extreme, biotopes such as groundwaters. Undernourishment experienced during ontogeny and/or postembryonic development has important consequences for life history (Brzek and Konarzewski, 2001) and, although instantaneous ecological consequences of poor and spotty nutrition (and/or hypoxia) are sometimes difficult to distinguish, the reproductive potential of any animals experiencing such conditions may become reduced so the effects will manifest at the population level. It is therefore hypothesized that several hypogean species possess specific behavioral, physiological and/or metabolic adaptations that allow them to successfully exploit subterranean environments. These features suggest that subterranean species are excellent models to study the effects and responses to prolonged fasting. Hervant et al. (1997) discovered that the hypogean aquatic isopod Stenasellus virei surviving prolonged fasting (exceeding 200 days) longer than the surface-dwelling species Asellus aquaticus and most other crustaceans previously studied. The hypogean amphipods Niphargus virei and N. rhenorhodanensis and the cave amphibian Proteus anguinus also showed high tolerance to starvation (Hervant et al., 1999b, 2001). During long-term fasting in these subterranean species, locomotory, ventilatory and metabolic rates were drastically reduced, whereas surface-related species exhibited only slight 2079 The Journal of Experimental Biology 205, 2079–2087 (2002) Printed in Great Britain © The Company of Biologists Limited 2002 JEB4141