| Abstract: | The amounts of 5-hydroxytryptamine (5-HT) in the skin of nine species of anurans were estimated by the fluorescence method. Relatively large quantities of 5-HT were found in the dorsal skin of five species of semi-terrestrial frogs, while in the skins of four highly aquatic species none, or only a trace, was found. Using the histochemical fluorescence method of Falck, 5-HT was located in the granules of the venom glands of Rana pipiens, a semi-terrestrial species, while no fluorescing glands were found in R. catesbeiana, a highly aquatic species. The results of Erspamer and others are discussed. It is suggested that the most probable role of 5-HT in frog skin is that of defense against land predators. |
