Behavioural, physiological and metabolic responses to long-term starvationand refeeding in a blind cave-dwelling (Proteus anguinus) and a surface-dwelling (Euproctus asper) salamander

The effects of long-term starvation and subsequent refeeding on haematologi cal variables, behaviour, rates of oxygen consumption and intermediary and energy metabolism were studied in morphologically similar surface- and cave -dwelling salamanders. To provide a hypothetical general model representing the responses of amphibians to food stress, a sequential energy strategy h as been proposed, suggesting that four successive phases (termed stress, tr ansition, adaptation and recovery) can be distinguished. The metabolic resp onse to prolonged food deprivation was monophasic in the epigean Euproctus asper (Salamandridae), showing an immediate, linear and large decrease in a ll the energy reserves. In contrast, the hypogean Proteus anguinus (Proteid ae) displayed successive periods of glucidic, lipidic and finally lipido-pr oteic-dominant catabolism during the course of food deprivation. The remark able resistance to long-term fasting and the very quick recovery from nutri tional stress of this cave organism may be explained partly by its ability to remain in an extremely prolonged state of protein sparing and temporary torpor. Proteus anguinus had reduced metabolic and activity rates (consider ably lower than those of most surface-dwelling amphibians). These results a re interpreted as adaptations to a subterranean existence in which poor and discontinuous food supplies and/or intermittent hypoxia may occur for long periods. Therefore, P. anguinus appears to be a good example of a low-ener gy-system vertebrate.