9630807 Hicks In contrast to the completely divided heart of birds and mammals, the heart of non-crocodilian reptiles (turtles, snakes and lizards) is made up of a single ventricle. This anatomical arrangement results in the mixing of oxygen-rich and oxygen-poor blood within the heart (cardiac shunting). Historically, this was viewed as an intermediate evolutionary step that was thought to be inferior compared to the circulation of birds and mammals. This perception changed in the later half of this century when studies showed that the amount of cardiac shunting is probably regulated and that cardiac shunts may provide several unique physiological advantages to reptiles. However, this notion of the reptilian circulation is based on a relatively small number of observations during specific types of behaviors or physiological states, for example during breathing. Utilizing technological advances in miniature blood flow measuring devices and computer assisted data collection systems, this research will measure a variety of physiological states including terrestrial locomotion, swimming, digestion and during periods of rest. This research provides an unprecedented opportunity to determine cardiac shunting patterns in reptiles during a variety of behaviors and physiological challenges and will make significant advancement towards understanding their unique cardiovascular "design".
