The structure of the skin of the tree frog (Hyla arborea arborea L.).

The aim of the study was to investigate the structure of the skin of the adult tree frog Hyla arborea arborea L. by scanning electron microscopy (SEM) and light microscopy (LM). SEM observation shows that the skin from the dorsal part of body is smooth whereas the ventral part has regular ridges and grooves. The superficial layer of the skin consists of irregular shaped epidermal cells covered with microridges differing on the dorsal and ventral skin. Two types of gland outlets, funnel-type and collar-type, are seen on the surface of the epithelium. The dorsal and ventral skin observed in LM contained three kinds of glands: mucous glands, and two different types of serous glands, type I and II. The mucous glands are small and located in the upper layer of the stratum spongiosum of the connective tissue. The serous glands are large. Type I glands with small secretory granules (1-3 microns) appear sporadically in both the dorsal and ventral skin. Type II glands with large secretory granules (5-15 microns) are very numerous, particularly in the dorsal skin. Many capillaries invaginate to the epidermis of the ventral skin facilitating absorption of water in these sites. The lipid glands occurring in the skin of phyllomedusine frogs are not observed in the skin of the tree frog.