Morphology and Histology of the Tongue and Oral Chamber of Eublepharis macularius (Squamata: Gekkonidae), with Special Reference to the Foretongue and its Role in Fluid Uptake and Transport

Abstract

Detailed descriptions of tongue morphology of members of Squamata that refer to functional implications other than food processing are rare. Herein we focus on the morphology of the dorsal epithelium and internal structure of the tongue of the Leopard Gecko, Eublepharis macularius, emphasizing the foretongue and its relation to fluid uptake. We employ both scanning electron microscopy and serial histology to examine the morphology of the entire tongue, its component regions, and its situation in the oral chamber. We recognize five distinct morphological regions of the dorsal tongue surface, each of which is distinctive both morphologically and histologically. The foretongue bears papillae quite different in structure and spacing from those of all other tongue regions, and these non-glandular structures are involved in gathering and transporting fluid from the environment. Fluid unloaded from the foretongue in the region of the vomeronasal sinus is channeled through the network of cuboidal papillae and directed towards a pair of compartments lateral to the tongue in which fluid pools during a drinking bout. This allows the dorsal surface of the mid-and hind-tongue, which are involved in food processing and manipulation, to be largely segregated from the pathway of fluid flow. We relate our findings to descriptions of the tongue of other taxa, and propose functional hypotheses for the observed morphology. This study provides new anatomical information upon which future studies of the functional morphology of the buccal apparatus in the Gekkota can be based.

Fine structure of the dorsal lingual epithelium in Tarentola annularis and Crocodylus niloticus

“…It has been referred that these substances are helping the tongue adhesion and swallowing of the food easily; this has been also documented in other vertebrates [6,24,41,49]. The tongue shows stronger reaction for protein stained with bromophenol technique in the lingual glands of C. niloticus compared with moderate reaction of T. annularis.…”

Comparative histological characterization of the tongue in two reptiles; Scincus scincus (Scincidae) and Uromastyx ornata (Agamidae) in relation to diet

“…Nasr et al (2012) mentioned that the presence of taste buds on the tongue tip of the rat may play an important role in receiving chemical and mechanical information of food. On other hand, some authors failed to detect taste buds in Eublepharis macularius (Jamniczky et al, 2009), in Podarcis sicula (Abbate et al, 2010), and in Ptyodactylus guttatus and Stenodactylus petrii (Darwish, 2012).…”

Reactions of green lizards (Lacerta viridis) to major repellent compounds secreted by Graphosoma lineatum (Heteroptera: Pentatomidae)

“…In this case, the aversive effect could be mediated by gustation, which is also well developed in green lizards (Schwenk, 1985;Cooper, 1991). The absence of any aversive effect of oxoaldehyde on leopard geckos (Gregorovičová andČerníková, unpublished data) may be related to their poorly developed sense of gustation (Schwenk, 1985;Jamniczky et al, 2009). On the other hand, oxoaldehyde has a strong aversive effect on birds (Gregorovičová et al, unpublished data), presumably due to their relatively well developed gustatory sense (Mason and Clark, 2000).…”