Independent evolution of squamate olfaction and vomerolfaction and correlated evolution of vomerolfaction and lingual structure

Publisher Website
Google Scholar
Abstract
The comparative abundances of chemoreceptor cells for olfaction and vomerolfaction, the sense mediated by the vomeronasal organs, were studied in numerous squamate families, with emphasis on lizards, and compared with abundance of lingual taste buds and aspects of lingual structure likely to be related to chemosensory sampling for vomerolfaction. Abundances of vomerolfactory receptors vary greatly among, but little within squamate families. Using Felsenstein's method of independent contrasts, the abundance of vomeronasal receptors is significantly correlated with size of lingual tines, degree of lingual elongation, and condition of sampling surfaces (pallets) on the ventral side of the tongue. This indicates that correlated evolution has occurred. An intimate relationship exists between the chemosensory organ and its primary sampling device, highlighting a lingual-vomeronasal complex that functions to sample and analyze chemical stimuli from external environmental surfaces. Attributes enhancing lingual facility for chemical sampling are forking, which permits scent-trailing by tropotaxis, and possibly elongation, which may permit greater extension beyond the mouth or enhance maneuverability. Ventral lingual pallets, surfaces that directly contact substrates during sampling, are large in forms having low abundances of vomerolfactory receptors, but are reduced and are eventually lost with progressive increases in vomerolfactory receptor abundance. Pallet condition is negatively correlated with tine size and lingual elongation. Large tines appear to take over the sampling function in forms lacking pallets. Lingual taste bud abundance is negatively correlated with vomerolfactory receptor abundance, forking, elongation, and positively with pallet condition. The negative correlation between the abundance of vomerolfactory receptors and lingual taste buds may be attributable to physical incompatibility between taste buds and specialized modifications of the foretongue for vomerolfactory sampling or to loss of opportunity for lingual taste buds to function in vomerolfactory specialists that lack lingual functions such as prey prehension, manipulation, and transport and in which the tongues are ensheathed while in the mouth. The abundances of olfactory and vomeronasal chemoreceptor cells are uncorrelated using Felsenstein's method. Thus, olfaction appears to have evolved independently of vomerolfaction.

This publication has 0 references indexed in Scilit: