Olfactory subsystems in the peripheral olfactory organ of anuran amphibians

JUNGBLUT LD; REISS, JOHN O.; POZZI AG

CELL AND TISSUE RESEARCH

SPRINGER

Año: 2021 vol. 383 p. 289 - 299

0302-766X

Anuran amphibians (frogs and toads) typically have a complex life cycle, involvingaquatic larvae that metamorphose to semi-terrestrial juveniles and adults. However,the anuran olfactory system is best known in Xenopus laevis, an animal withsecondarily aquatic adults. The larval olfactory organ contains two distinct sensoryepithelia: the olfactory epithelium (OE) and vomeronasal organ (VNO). The adult organcontains three: the OE, the VNO, and a ?middle cavity? epithelium (MCE), each in itsown chamber. The sensory epithelia of Xenopus larvae have overlapping sensoryneuron morphology (ciliated or microvillous) and olfactory receptor gene expression.The MCE of adults closely resembles the OE of larvae, and senses water-borneodorants; the adult OE is distinct, and senses air-borne odorants. Olfactorysubsystems in other (non-pipid) anurans are diverse. Many anuran larvae show apatch of olfactory epithelium exposed in the buccal cavity (bOE), associated with agrazing feeding mode. And other anuran adults do not have a sensory MCE, but manyhave a distinct patch of epithelium adjacent to the OE, the recessus olfactorius (RO),which senses water-borne odorants. Olfaction plays a wide variety of roles in the life oflarval and adult anurans, and some progress has been made in identifying relevantodorants, including pheromones and feeding cues. Increased knowledge of thediversity of olfactory structure, of odorant receptor expression patterns, and of factorsthat affect the access of odorants to sensory epithelia, will enable us to betterunderstand the adaptation of the anuran olfactory system to aquatic and terrestrialenvironments.