Comparative studies on the ultimobranchial body in reptiles and birds

Abstract

This is a second in a series of experiments involved in a comparative histological study of the ultimobranchial body in vertebrates. Reference is made to its glandular structure in selected specimens of turtles, lizards, snakes, and birds; its alleged functional relationship with the thyroid gland was also investigated with radioisotopes. No morphological resemblance by the ultimobranchial tissues to the thyroid parenchyma was observed in any of the specimens examined, though some similarity to the cellular structure of the parathyroid and thymus glands is recognizable in certain snakes and birds. Examination of autoradiographs prepared from I 131-treated specimens disclosed that the ultimobranchial body does not metabolize iodine. There is evidence, however, that the gland is capable of considerable physiological activity, i.e., synthesis of glycogen, mucopolysaccharides (sulfated and neutral), phospholipids, and other protein complexes, as demonstrated by Alcian blue-PAS, toluidine blue, Sudan black B, Millon's, and ninhydrin staining methods. Evidence for the presence of sulfated mucopolysaccharides is supported by the retention of S 35 within the secretion of the gland. An apparent influence of seasonal changes in the secretory activity of the ultimobranchial body in lizards (and possibly in other reptiles) is indicated by an increase of the secretory product in both content and density from June to September as well as an apparent increase in the relative amounts of glycogen and mucopolysaccharides in the gland.