The Influence of the Hypophysis and the Thyroid on the Ultimobranchial Body of the Anura of Israel

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Abstract
The ultimobranchial body of Hyla arborea L., Rana ridibunda Pall., Pelobates syriacus Boettger, and Bufo viridis Laur., the common anurans of Israel, is a paired organ, situated on both sides of the aditus laryngis. Its development runs parallel to the fluctuating activity of the thyroid (Boschwitz, 1960). (a) In the premetamorphic period of relative thyroid dormancy, the ultimobranchial body consists of one follicle with single-layered epithelium in Hyla, Rana, and Bufo, and of a coiled tube with parafollicular cells in Pelobates. A capsule with capillaries surrounds the organ. (b) In the period of metamorphosis up to the beginning of tail-resorption, during which thyroidal activity is heightened, the epithelium of the ultimobranchial body becomes pseudostratified, and the size of the follicle enlarges. In Pelobates the coiled tube changes into several single-layered follicles with parafollicular cells. The whole organ becomesless dispersed. The follicles of all 4 species contain a small amount of faintly eosinophilic coagulum, and often normal-appearing nuclei are embedded therein.