Presence of pigment in the ovine pineal gland during embryonic development.

Light- and electron-microscopic analyses were used to identify and describe the characteristic features of cells containing pigment in the ovine pineal gland during prenatal development. 72 ovine embryos (36 male, 36 female) ranging in age from 54 to 150 days were used for this study. Cells containing pigment granules were a constant feature in this gland. When samples from the different groups were inspected using the naked eye, the detection of pigment was of 61% in groups I (54 to 67 days of prenatal development) and II (71 to 92 days of prenatal development), 83% in group III (98 to 113 days of prenatal development) and 25% in group IV (118 to 150 days of prenatal development). The morphological features and histochemical properties of the pineal pigment enabled it to be identified as melanin. Several types of pigment granules were ultrastructurally distinguished; these varied in size, shape and location within pineal cell populations. The pigment granules were detected in pinealocytes, interstitial cells and pigmented cells. The largest amount and the widest variety of pigmented granules were found in pigmented cells. The presence of cells containing pigmented granules amongst the cell populations of the developing ovine pineal gland was analysed and compared with that of other mammalian species.