Antidiuretic Activity in the Pituitary Gland of the Koala Bear

ARGININE or lysine vasopressin is found in the pituitaries of most placental mammals and arginine vasopressin has been tentatively identified in a monotreme1and in four species of marsupials1,2. We have investigated antidiuretic activity in the pituitary of a young koala bear (Phascolarctos cinereus), which is of interest because this animal is rarely, if ever, known to drink, its water intake being derived solely from eucalyptus leaves.