A comparative optical microscopic and ultrastructural study on the ultimobranchial (UB) glands of three common species of Israeli anurans:Bufo viridis, Hyla arborea, andRana ridibundaduring metamorphosis is presented. The UB glands typically consist of a single follicle with a central lumen, though occasionally secondary follicles are present inHylaandRana.A single UB cell type is found which appears either in a very electrondense “dark” form or as a less dense “light” form, though the ratio of dark: light cells from gland to gland at any one stage of metamorphic development is quite variable. By the end of metamorphosis inBufoandHylaall the UB cells are usually of the light variety, whereas inRanathe dark cells persist. The organelles of these secretory cells including secretory granules, granular endoplasmic reticulum, free ribosomes, tonofilaments, microtubules, Golgi bodies, and lipid droplets, their distribution, abundance, and possible functions in relation to metamorphosis are described. Apocrine secretion into the central lumen of the gland is also described and di
展开▼
