Catalina Reyes

PhD candidate (UBC) MSc Zoology (UBC) BSc (Los Andes University, Colombia) Contact Info: Department of Zoology University of British Columbia 6270 University Blvd. Vancouver, British Columbia Canada, V6T 1Z4 Tel: (604) 822-5799 FAX: (604) 822-2416 reyes@zoology.ubc.ca

Peripheral chemoreceptors in reptiles and their role in cardiorespiratory control

Reptiles encounter hypoxic and hypercapnic environments on a daily and seasonal basis (diving, burrows and dormancy). In order to maintain blood gas homeostasis under these conditions, adjustments in both the cardiovascular and respiratory systems occur. Control systems such as those incorporating the central and peripheral chemoreceptors are responsible for monitoring the level of blood gases and adjusting ventilation and perfusion to meet metabolic demands. Breathing in reptiles appears to be highly affected by peripheral chemoreceptor input, while in mammals these receptors only play a modulating role. In all vertebrates, aortic and carotid bodies (peripheral chemoreceptors) associated with oxygen and CO2/H+ sensing are characterized by an association of glomus cells, sustentacular cells and nerve terminals. The location and innervation of these structures varies widely between vertebrate groups. Structures homologous to the carotid bodies in mammals have not yet been localized in reptiles. Few studies have found several chemoreceptive sites in the truncal region of turtles. Indirect evidence suggests that chemoreceptors in lizards are located in the carotid arch, but unlike turtles, no other chemoreceptive area has been investigated and chemoreceptive function is unknown.

My research aims to 1) locate and characterize the ultrastructure, innervation and putative neurotransmitters of peripheral chemoreceptors in different groups of reptiles so that homologies with those of other vertebrates can be derived; and 2) establish the role of different chemoreceptive sites in ventilatory regulation and cardiovascular control. I will test whether distinct populations of chemoreceptors sense oxygen tension or O2 content and differ in their regulatory roles. Specifically, I will ask whether multiple chemoreceptive sites are advantageous for reptiles that regulate blood gases by changing ventilation and/or the degree of cardiac shunt. My study will examine if O2-sensing structures are highly conserved among vertebrates, while the location (multiple O2-sensing sites) changed so that a more effective ventilatory or cardiovascular control can be exerted in animals with cardiac shunts such as reptiles.

Last updated: 8 December, 2008