THE PARATHYROID-GLANDS OF 2 SPECIES OF DOLPHIN - RISSOS DOLPHIN, GRAMPUS-GRISEUS, AND BOTTLE-NOSED-DOLPHIN, TURSIOPS-TRUNCATUS

Although there have been many reports regarding the structure of the p arathyroid glands of various terrestrial mammals, little is known abou t the parathyroid glands of marine mammals including Cetacea. The morp hology of the parathyroid glands of three Risso's dolphins, Grampus gr iseus (about 3 m in length and 300 kg in weight), and three bottlenose dolphins, Tursiops truncatus (about 3 m in length and 300 kg in weigh t), was examined macroscopically and microscopically The dolphins exam ined in the present: study had two or four parathyroid glands that var ied in size and location on the thyroid gland. Each parathyroid gland was encapsulated by fibrous tissue on the dorsal surface of the thyroi d gland, and was divided into several lobules by interlobular connecti ve tissue which contained numerous capillaries. The parenchymal cells consisted of pale staining chief cells. Each cell was polygonal and ab out 15 mu m in diameter, and had one round or oval nucleus. Oxyphil ce lls were not found. Considering their greater body size, the parathyro id glands were rather small. By electron microscopic observation, the pararthyroid gland of the bottlenose dolphin had sparse granular endop lasmic reticulum, poorly developed Golgi complexes, and abundant secre tory granules in the cytoplasm of the chief cells. These results suppo rt a possibility that the activity of the parathyroid gland is suppres sed to adapt to a sea habitat. (C) 1998 Academic Press.