Response patterns and neurogenesis of the olfactory bulb of Xenopus laevis during metamorphosis

Abstract

Amphibians possess the ability to smell in water and land. This dual ability requires massive modifications in the aquatic larva to the terrestrial adult life in the olfactory system during its development. In the larva of Xenopus laevis, the principal cavity in the olfactory epithelium detects waterborne odors and projects its axons to the ventral olfactory bulb. During metamorphosis the principal cavity is remodeled and transformed into the adult air nose which sends its axons to a newly build enlarged dorsal olfactory bulb. Meanwhile, the development in the olfactory epithelium of a new cavity occurs: the middle cavity and effectuates the role of a water nose. The sensory cells lining in the middle cavity extend their axons into the ventral olfactory bulb. In this project we undertook a stage-by-stage survey of the anatomical changes and odorant response profiles in the olfactory bulb of Xenopus laevis during metamorphosis to follow its anatomical changes and its functionality throughout development. The undisrupted functionality of the ventral olfactory bulb means that Xenopus is capable of smell while it undergoes metamorphosis, which is a relevant behavioral advantage for survival. This means that Xenopus laevis can feed, avoid danger and migrate when necessary. The changes taking place in the olfactory system in amphibians during metamorphosis provide valuable insights into the de novo formation and reorganization of functional neuronal networks.