ULTRASTRUCTURAL-STUDY OF POSTHATCHING DEVELOPMENT IN THE PINEAL-GLANDOF THE JAPANESE-QUAIL

The pineal gland of the Japanese quail(Coturnix coturnix japonica) ret ained numerous follicular structures, each of which was composed mostl y of pinealocytes and supporting cells radially arranged around the fo llicular lumen during the first 6 weeks of age. In the pinealocytes, p araboloids and regular stacks of lamellar disks: which were demonstrat ed at 1 day of age in a previous study [14], rapidly decreased in numb er after 1 week of age. From 1 to 6 weeks of age, the pinealocytes had more developed lamellar whorls in the follicular lumen with the incre ased numbers of mitochondria in their apical protrusions and synaptic ribbons in their basal processes. In addition to these photosensory el ements, pigment-containing cells occasionally accumulated in the basal side of the follicular structure. Their pigment granules, which were considered as melanin, gradually became larger and more roundish in sh ape after 1 week of age. The histological elements associated with the secretory function of the quail pineal were dense-cored vesicles and lysosomes in the pinealocytes and dense bodies in the supporting cells . The synaptic ribbons and the dense-cored vesicles in the pinealocyte s rapidly increased in number at 1 week of age, scarcely exhibiting di stinct changes thereafter. Thus, it is clarified that the foregoing ph otosensory and secretory elements change during the post-hatching deve lopment. Furthermore, it is suggested that, in respect of these elemen ts, the pineal gland of the quail assumes more active appearances than that of the chicken.