Plasma T3 and T4 levels in a snake, Elaphe taeniura

Abstract

The plasma thyroid hormones (TH) in the snake, Elaphe taeniura, were studied using RIA. Samples of plasma were obtained from untreated snakes in March, May and September as weU as thyroidectomized snakes in May. Scale biopsies were taken from each snake in order to see if there were any correlations of plasma T3 and T4 levels and epidermal changes during the sloughing cycle. Plasma samples were also taken from another snake species Ptyas korros and a chelonia sp. Clemmys mutica for comparison. Data showed that the plasma T3 and T4 levels of these reptilian species were very low (less than 1 nmol/1) and there were extensive individual variations (from below detection to 0.910 nmol/1). There were seasonal variations in these levels in E. taeniura. One week after thyroidectomy, the plasma levels of T3 and T4 could not be detected, suggesting that the thyroid gland is the only source of thyroid hormones in the snake. There was no correlation between mean plasma T3 and T4 levels during the resting and renewal phase. The extreme low level of plasma T4 preceding, and its absence following thyroidectomy which always precipitates, the renewal phase provide circumstantial support to the inhibitory role of TH on epidermal proliferation/differentiation in sloughing.