Olfactory epithelium ontogenesis and function in postembryonic North American Bullfrog (Rana (Lithobates) catesbeiana) tadpoles

Canadian Journal of Zoology, e-First Articles. During metamorphosis, the olfactory system remodelling in anuran tadpoles — to transition from detecting waterborne odorants to volatile odorants as frogs — is extensive. How the olfactory system transitions from the larval to frog form is poorly understood, particularly in species that become (semi-)terrestrial. We investigated the ontogeny and function of the olfact ory epithelium of North American Bullfrog (Rana (Lithobates) catesbeiana Shaw, 1802) tadpoles at various stages of postembryonic development. Changes in sensory components observable at the epithelial surface were examined by scanning electron microscopy. Functionality of the developing epithelium w as tested using a neurophysiological technique (electro-olfactography (EOG)), and behaviourally, using a choice maze to assess tadpole response to olfactory stimuli (algae extract, amino acids). The youngest (premetamorphic) tadpoles responded behaviourally to an amino acid mixture despite having un derdeveloped olfactory structures (cilia, olfactory knobs) and no EOG response. The consistent appearance of olfactory structures in older (prometamorphic) tadpoles coincided with reliably obtaining EOG responses to olfactory stimuli. However, as tadpoles aged further, and despite indistinguishable differences in sensory components, behavioural- and EOG-based olfactory responses were drastically reduced, most strongly near metamorphic climax. This work demonstrates a more...
Source: Canadian Journal of Zoology - Category: Zoology Authors: Source Type: research