Effect of Acute Captivity Stress on Plasma Concentrations of Corticosterone and Sex Steroids in Female Whistling Frogs, Litoria ewingi

Abstract

Plasma concentrations of corticosterone and sex steroids were examined in vitellogenic frogs (Litoria ewingi) at 0, 0.5, 3, and 24 hr after capture from the wild. Plasma corticosterone concentrations were undetectable (<1.8 ng/ml) in all frogs at capture and rose significantly as time in captivity increased (P < 0.05). Plasma concentrations of estradiol (1001 ± 13 pg/ml) and testosterone (4.0 ± 0.7 ng/ml) did not change after capture (P ± 0.05). Plasma progesterone concentration varied slightly after capture (P = 0.046) but this was of doubtful significance. Concentrations of corticosterone did not significantly correlate with estradiol, testosterone, or progesterone concentrations during 0-24 hr after capture. These results and previous studies indicate considerable variation among the sex steroid responses of female amphibians to capture. We suggest that the stage of vitellogenesis may modulate the amphibian response to captivity stress.