Local Metamorphosis of Larval Skin in Rana pipiens

Abstract

Cholesterol pellets containing 20% thyroxine, implanted under the skin or in the cranial cavity of young tadpoles, are shown to stimulate the adjacent skin to undergo metamorphic changes. The extent of skin transformation near the pellets is much greater than farther away. Generally changes can be detected up to 3 mm. from the pellet site, for pellets of about 0.25 mg. Local changes include complete glandular development, adult spot formation, stratification of the epidermis, and molting. Some thyroxine also gets into the blood stream, and brings about a short, moderate, generalized metamorphic stimulation; but in no case did genera development proceed to the level at which normal skin trans-formation changes might be expected. The pellets seem to lose all thyroxine in 10-14 days, and many tadpoles then enter a period of metamorphic stasis.