Evolutionary morphology of the lizard chemosensory system
Baeckens, Laboratory Of Functional Morphology, Department Of Biology, University Of Antwerp, Universiteitsplein, Wilrijk, Department Of Organismic, Evolutionary Biology, Harvard University, Cambridge
Variation in vomeronasal-lingual morphology Squamates use their vomeronasal-lingual system to sample chemicals from the surroundings47,48. Since bifid tongues may enhance tropotactic scent-trailing19 and since a thick sensory epithelium might increase the functionality, discriminatory ability, reliability and sensitivity of the VNO47,48, it is tempting to infer this co-variation between ‘sampler’ and ‘sensor’ as a functional ‘optimization’ of chemosensory design. This might be an explanation of why the average degree of tongue bifurcation of lacertids (T FS ) is 4.2 times smaller than those of varanids (following Schwenk19). While the present study was unable to find an association between foraging activity and the chemosensory design of lacertids, it did establish a link between a lizards’ investment in chemical signalling and the morphology of their vomeronasal-lingual system. Our findings showed a relationship between tongue form and VNO sensory epithelium thickness of lacertids, and their investment in secretion production: species that carry many secretory glands and are able to produce large amounts of secretion, have on average a thin layer of VNO sensory epithelium and long, broad tongues that are only marginally forked (Fig.