The ultrastructure of the pituitary and the adrenal gland of three newborn marsupials (Dasyurus hallucatus, Trichosurus vulpecula and Isoodon macrourus).

The ultrastructure of the pituitary glands of the newborn northern native cat, brushtail possum and the northern brown bandicoot and the adrenal glands of the former two marsupials were examined to determine whether these endocrine glands were functional at birth. The anterior pituitary of all three species was well vascularised and many cells contained electron-dense, membrane bound granules. The adrenal glands were composed of two distinct cell populations. One group of cells possessed dark staining granules, normally observed in catecholamine-secreting cells, and the second group contained large amounts of smooth endoplasmic reticulum and mitochondria with tubulovesicular cristae, indicative of steroid hormone secreting cells. The ultrastructure of the cells of the fetal pituitary and adrenal of all three species would suggest that these glands are functional at birth and, as with many eutherians, the marsupial pituitary and adrenal gland may play an important role in determining the length of gestation.