The ontogeny of nasal chemical senses in garter snakes.

The development of the nasal chemical senses of reptiles is of particular interest since evidence suggests that neonatal reptiles use both their olfactory and vomeronasal systems. This review focuses on the embryonic development of these nasal chemosensory systems in garter snakes (Thamnophis spp.). Three approaches have been used to examine development: (1) Normal morphological studies, (2) 3H-thymidine autoradiographic studies, and (3) metabolic mapping of the accessory and main olfactory bulbs with cytochrome oxidase histochemistry. In addition, garter snake embryos have been grown in vitro to facilitate experimental procedures. The results of these studies show that reptiles are a rich and diverse group for investigating the developmental processes that form the neurobiological basis for naturally occurring chemosensory-mediated behaviors.