P1.216 Wednesday, Jan. 4 Vascular patterns in iguanas: blood vessels and cephalic sites of thermal exchange PORTER, W. R.*; WITMER, L. M.; Ohio University; Ohio University firstname.lastname@example.org
Reptilian physiological research has shed light on the behavioral and physiological components of thermoregulation, yet no modern anatomical investigation has mapped vascular anatomy onto areas of potential thermal exchange. Archosaurs and mammals have been shown to use these sites to support selective temperature regulation, indicating that blood vessels are used in a similar manner across clades. Our understanding of similar concepts in reptiles, however, is incomplete. Vascular anatomy was investigated in the green iguana, with special attention to known sites of thermal exchange. Blood vessels were injected with a latex/barium solution of differing concentrations to discriminate arteries from veins in CT scans. Specimens were scanned using the OUµCT scanner at 90-micron slice thicknesses and analyzed using Avizo. The palatal plexus was less extensive than the archosaur plexus. The tongue was found to be highly vascularized, with vessels concentrated just ventral to the choana, possibly exposing blood vessels to airflow from the nasal cavity. Blood supply to the nasal cavity is from the supraorbital and ethmoid arteries with collateral supply via the palatal and maxillary arteries. These arteries anastomose around the nostril to form a narial plexus, exposing blood to ambient temperatures. A similar vascular pattern was found in the narial regions of archosaurs. The veins of the nasal cavity empty into the orbital sinus along the rostroventral border of the frontal bone. The orbital sinus surrounds the globus oculi and then coalesces into the jugular vein along the caudal aspect of the orbit. These results indicate that iguanas use similar sites of thermal exchange as archosaurs, suggesting that an ability to finely regulate cephalic temperatures may characterize all diapsids.