Filoramo, N.I.*; Schwenk, K.: Ultrastructure of the lingual surface in anguimorph lizards and snakes: evolutionary and functional implications.

In squamates, one of the tongue’s roles is to collect chemicals from the environment. Both volatile and non-volatile chemicals are delivered to the vomeronasal chemosensory organs (VNOs). The information gained from these chemicals allows squamates to find and identify mates and prey items. Given the tongue’s central role in delivering chemicals to the VNOs, understanding the surface topology of the tongue and how it might affect the tongue’s ability to retrieve environmental chemicals and deliver them to the VNOs is of high import. This study focuses on anguimorph lizards and snakes, whose tongues have become highly modified for their role in chemoreception. Snakes are widely believed to have evolved from within the Anguimorpha. Both scanning and transmission electron microscopy where employed. The surface topology of the forked region of the tongue (the tines) differs from that of posterior, unforked region of the tongue in all specimens investigated to date. The surface topology of the tines in snakes differs significantly from those of anguimorph lizards. In snakes, the tine surfaces are covered with microfacets. However, in most anguimorph lizards both the dorsal and ventral surfaces are covered depressions and the ventral surfaces have scattered small or “incipient” microfacets. Helodermatids are an exception in that instead of scattered incipient microfacets on the ventral surfaces of the tines there are clusters of larger, snake-like, microfacets. Ultrastructural features suggest that the deeply forked tongues of snakes and varanids were derived independently. Biomechanical evidence suggests that ultrastructural differences may be unrelated to function.