[Immunohistochemical and morphometric studies on the development of the thyroid, parathyroid and ultimobranchial body in Xenopus laevis Daudin]

The development of the thyroid, parathyroid and ultimobranchial body was examined by immunohistochemistry and morphometric analysis in the larvae of Xenopus laevis Daudin from the time immediately after hatch to the end of metamorphosis. The thyroid appeared at stage 43 and began to secrete thyroglobulin from stage 47/48. Both the volume of the thyroid and the height of the follicular epithelium reached the peak at stage 61 and decreased thereafter towards the end of metamorphosis at stage 66. The parathyroid first appeared at stage 43 as the thickening of the wall of the third and fourth visceral pouch. The volume of the parathyroid gradually increased with the progress of development until the end of metamorphosis. The ultimobranchial body appeared at stage 45 as a recess of the epithelium lining the floor of the pharynx. It became follicular in the structure at stage 53. Its volume reached the peak at stage 61 and decreased thereafter towards the end of metamorphosis. Calcitonin-immunoreactive cells first appeared in the ultimobranchial body at stage 47/48, showed the most intense reaction at stage 59, and rapidly decreased in number thereafter towards the end of metamorphosis.