EFFECT OF DESOXYCORTICOSTERONE ACETATE ON METAMORPHOSIS INDUCED BY THYROXINE IN ANURAN TADPOLES

Abstract

Effects of desoxycorticosterone acetate (DCA) on thyroxine-induced metamorphosis were studied. When tadpoles at hind limb-bud stage are treated with DCA alone, their metamorphosis is completely inhibited. DCA seems to inhibit development of functional activity of the thyroid gland in the tadpoles at this stage. But when thyroxine and DCA are given simultaneously, the steroid accelerates the water loss as well as the following degenerative changes of thyroxine-induced metamorphosis: decrease in the length of trunk and tail, resorption of tail fin and opercular perforation. On the other hand, it antagonizes slightly but significantly the effect of thyroxine on anabolic changes such as the growth of forelegs and hind limbs. It is suggested that the ratio of circulating amounts of thyroxine and mineralocorticoids is important in regulating the metamorphosis of anuran tadpoles.