Relationship between the preoptico hypophysial system and the vascular system in the teleost Rita rita (Ham.).

In Rita rita the internal carotid artery gives rise to hypothalamic and hypophysial arteries. The hypophysial artery directly enters the pituitary and largely contributes to the interface vasculature lying in between the neurohypophysis and the pars distalis which can be considered as an equivalent of the median eminence. Blood vessels from the interface vasculature enter the pars distalis. The hypothalamic artery gives rise to the primary capillary plexus in the infundibular floor and the portal vessels formed by it irrigate the glandular pituitary. Both, at the level of the hypothalamus and at the interface, neurosecretory material might get access to blood vessels. Thus, in Rita rita, not only the typical teleostean type of hypothalamo-hypophysial vascularization is present, but also an incipient tetrapodal pattern is evident.