Abstract

There are reports describing the gross, histologic and ultrastructural anatomy of the cetacean pituitary dating back to the late 1800s. However, the observations have usually been based on only one or a few animals. Pathological abnormalities of the cetacean pituitary have rarely been described. The purpose of this study was to identify abnormalities in the adenohypophsis, or anterior pituitary, of stranded cetaceans.

Full necropsies were performed between 1991-2000 on freshly stranded cetaceans collected by the Texas Marine Mammal Stranding Network under a permit from the National Marine Fisheries Service. Fifty-eight pituitaries were collected from nine species ranging from neonate to adult. Cross or longitudinal sections were stained with hematoxylin and eosin (H&E); hematoxylin, phloxine and saffron (HPS) and with PAS-Orange G.

Colloid containing follicles were a prominent feature in most pituitaries, occurring in forty four of the 47 T. truncatus all in non-Tursiops species examined except for a juvenile M. europaus. All T. truncatus without colloid in the adenohypophysis were less than 138 cm in length. Colloid was most commonly present as small to intermediate follicles (n=51) but larger cysts occurred in 23 of the animals. The colloid follicles and cysts were surrounded by cells with stellate processes and flat, elongated nuclei. Distribution of follicles was throughout the pituitary in well defines zones but they were most commonly associated with the stalk (pars tuberalis) region. With one exception, cysts were always posterior but centrally located and frequently extended laterally through the wings of the adenohypophysis. One cyst extended 24 mms in a 28 mms wide pituitary. Several of the cysts were macroscopically visible.

Psamomma bodies (lamellar calcifications) were observed in 22 T. truncatus (16 females, 6 males), a juvenile female M. europaeus and a female S. bredanensis. The smallest T. truncates in which these calcifications occurred was 196 cm. All but one was observed to have colloid in the pituitary and twelve of these cases also had the large colloid cysts described above.

Hyperplastic nodules occurred in nine T. truncatus (4 male, 5 female) but none were identified in other species. All but one of the hyperplastic nodules were in animals greater than or equal to 215cm in length, the other occurred in neonate. A squamous cyst and cholesterol clefts were observed in a 240 cm female. A male T. truncatus also had cholesterol clefts formed in the pituitary. One case of hyperpituitarism associated with hypogonadism also was documented.¹

Reference

1.  Haubold, E.M., and D.F. Cowan, 1998. Sterility in an Atlantic bottlenose dolphin (Tursiops truncatus) with a hypertrophic pituitary and hypogonadism. Proceedings of the 29th Annual International Association for Aquatic Animal Medicine Conference. San Diego, CA. Pg. 63.