Vertebrates may control heat transfer with the environment by differentially changing heart rate and blood flow during heating and cooling. In reptiles, the ecological benefit of this physiological thermoregulation is a pronounced increase in the time spent at a "high" body temperature during the day. During heating and cooling in a lizard, the cardiovascular system is controlled by prostaglandins and to a lesser extent by the autonomic nervous system. There are, however, pronounced phylogenetic differences in cardiovascular control mechanisms of thermoregulating reptiles. Additionally, the characteristic heart rate "hysteresis" pattern also occurs in a crustacean, pointing towards parallel evolution of control mechanisms alongside increasing vascularisation.
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