VASCULARIZATION OF THE PINEAL COMPLEX IN THE LIZARD TILIQUA-RUGOSA

The vascularization of the pineal complex in the lizard Tiliqua rugosa was investigated by vascular corrosion and latex casting techniques. The fine structure of the pineal capillaries was also studied by trans mission electron microscopy. The pineal complex in T. rugosa consists of an elongated pineal gland proper and a separate, distinct parietal eye. The pineal complex derives an abundant blood supply from branches of the middle and posterior cerebral arteries. Scanning electron micr oscopy of vascular corrosion casts revealed a dense and extensive pine al capillary bed which drains ultimately into a wide longitudinal sinu s suggesting an efficient pathway for the rapid removal of substances secreted by the gland. The parietal eye, which receives a unilateral l eft-sided blood supply from the unpaired anterior pineal artery, is sh own to be a highly vascularized structure. The close morphological rel ationship between the pineal gland and dorsal sac, where the two struc tures apparently share the same blood vessels, suggests a functional r elationship between them. The pineal capillaries are fenestrated with tight junctions between adjoining endothelial cells. Podia-like ablumi nal extensions of the endothelial cells were observed in close relatio n to unmyelinated nerve bundles. The basal margin of the pineal parenc hyma is highly invaginated with thin finger-like cytoplasmic protrusio ns into the pericapillary space. Distinct bands of microfibrils form ' 'struts'' anchoring the pineal parenchyma to the endothelial wall. The se features may have a role in the transfer of materials between the p ineal gland and the blood stream.