Nychthemeral variations of plasma corticosteroids in captive female Lacerta vivipara Jacquin: influence of stress and reproductive state.

This work was designed to study nychthemeral variations of plasma corticosterone and aldosterone in captive female lizards Lacerta vivipara. In preliminary experiments, the possible alterations of plasma corticosteroids by various stress factors were researched. A prolonged blood sampling (up to 8 min) did not alter plasma corticosterone levels but a significant increase of plasma aldosterone levels was observed. Confinement (1 or 18 hr) in small individual cages before blood collection resulted in a significant increase of both corticosterone and aldosterone. Whatever the period investigated (vitellogenesis, gestation, 2 months after parturition), plasma corticosterone levels showed a unimodal daily rhythm correlated with the activity of the females in the laboratory. No shift of the peak was observed according to season but the mean minimal and maximal levels were lower during vitellogenesis than during the other periods tested. Nychthemeral variations of plasma aldosterone levels were similar to those of corticosterone but of lower amplitude. Adrenal response to a short confinement (less than 1 hr) before blood sampling varied during a 24-hr period (period tested: vitellogenesis). Only minimal levels of corticosteroids were significantly increased. The possible effects of a long duration of captivity under optimal thermal conditions are discussed.