Meeting Abstract

50.5  Jan. 6  Hydraulic Delivery of Chemicals to the Vomeronasal Organs in Squamate Reptiles: A Comparative Morphological Study FILORAMO, N.I.; SCHWENK, K.**; Univ. of Connecticut, Storrs; Univ. of Connecticut, Storrs kurt.schwenk@uconn.edu

Despite growing evidence for the importance of vomeronasal chemoreception in the sociobiology of lizards and snakes, the biomechanics of this process are poorly understood. Vomeronasal chemoreception can be divided into three mechanical tasks: retrieval (transfer of environmental chemicals to the tongue tips); stage 1 delivery (delivery of chemicals into the oral cavity near to the vomeronasal fenestrae); stage 2 delivery (delivery of chemicals into the vomeronasal organs). Retrieval occurs through diffusion of scent molecules into the fluid covering the tongue tips. Stage 2 delivery is caused by suction generated within the VNOs. The prevailing theory of stage 1 delivery is based on snakes. It suggests that the forked tongue tips are wiped against sublingual plicae on the floor of the mouth as the tongue is retracted; the plicae are then elevated against the palate and the vomeronasal fenestrae. Snakes are highly derived compared to most lizards in having reduced, narrow, forked tongues that are retractile within a sheath and modified, pronounced sublingual plicae, making the generality of this theory questionable. In most lizards the tongue is not forked, is non-retractile and the sublingual plicae are unmodified or weakly developed. We show that there is complementarity of upper and lower mouth surfaces reflecting the shape of the foretongue. At closure, palatal glands and sublingual plicae are apposed, sealing the tongue within a snug-fitting chamber. We suggest that chemical-laden fluids on the tongue tip surfaces are transported instantaneously, either through compression or capillarity, to the vomeronasal fenestrae. Elevation and compression of sublingual glands might express fluid dorsad, flushing the tongue tips and aiding this process.