Mechanics and kinematics of fluid uptake and intraoral transport in the leopard gecko

Abstract

Drinking permits amniote vertebrates to compensate for water loss. Lizards (nonophidian squamates) use their tongue to imbibe water, but for most lizards the tongue is also employed in other activities. To determine how these various demands can be accommodated alongside the tongue's role in drinking, it is necessary to firstly determine the tongue's function in water uptake and intraoral transport in a lizard that does not use this organ for chemoreception or food prehension. We selected the leopard gecko (Eublepharis macularius) for this purpose. We build upon previous morphological observations of the anatomy of its tongue and oral cavity and explore its drinking behaviour through high-speed cinematography and cineradiography. This allows us to follow the movement of radio-opaquely labelled water in association with tongue, jaw and throat movements. The tongue is modified to collect water and to release it into the anterior region of the buccal cavity. Repeated tongue cycles are associated with the shifting of the imbibed water into paired ventrolateral chambers and ultimately to its passage to a single, midline posterior chamber prior to swallowing. Tongue movements, capillarity and pressure changes due to hyolingual movements cause water to be moved posteriorly along specific pathways prior to swallowing, bypassing the airways and dorsal surface of the mid-and hind tongue. In this licking-based lingually driven approach to drinking, only small volumes of water can be gathered at a time, with a drinking bout consisting of 20-30 tongue cycles before emersion and swallowing occur. This mechanism differs from drinking in turtles and snakes, which do not employ licking and may take in larger quantities of water. We advance the hypothesis that all lizards have conserved this pattern of tongue-based water uptake and precisely directed intraoral fluid transport, with specializations for tongue-based food capture and/or lingually based chemoreception being superimposed thereupon.

Morphological characteristics of the blackspot seabream (Pagellus bogaraveo) tongue: A structural and immunohistochemical study

“…It has been shown that the capacity and modality of feeding are strictly related to the morphofunctional adaptations of fish to the environment, thus explaining the several differences observed in the presence, morphology, abundance and distribution of taste buds, papillae with mechanic or sensitive properties and teeth of different shapes in several species of fish (Abbate et al, 2006(Abbate et al, , 2017(Abbate et al, , 2020b(Abbate et al, , 2020a(Abbate et al, , 2012b(Abbate et al, , 2012aGermanà et al, 2009;Amato et al, 2012;Dos Santos et al, 2015;Sadeghinezhad et al, 2015;Guerrera et al, 2015 ;Mahmoud et al, 2016;Kettratad et al, 2017;Levanti et al, 2017;Ik pegbu et al, 2019;Kasumyan, 2019). Also, a strict comparative correlations with numerous studies carried out in other vertebrates like birds and reptiles are significative (Abbate et al, 2020c(Abbate et al, , 2010(Abbate et al, , 2009(Abbate et al, , 2008Erdoğan and Alan, 2012;Erdoğan and Iwasaki, 2014;Herrel et al, 2014;Cizek et al, 2019;Bels et al, 2020). In addition, recent data demonstrate that the role of some hormones is strictly related to the anatomical aspects of the digestive system and particularly of the teleosts oral cavity (Montalbano et al, 2016(Montalbano et al, , 2018aMania et al, 2017;Audira et al, 2018;Carnovali et al, 2018).…”

Anatomical, histological and immunohistochemical study of the tongue in the rainbow trout (Oncorhynchus mykiss)

“…The most of the functional processes inside the oral cavity are carried out by the tongue, whose presence and description have been showed in different species of fish, demonstrating the variation in the presence of anatomical structures like taste buds, mucous cells and teeth in teleosts, also of commercial interest (Abbate et al., 2006,2017,2020a,2020b; Abbate, Guerrera, Montalbano, Ciriaco, et al., 2012; Abbate, Guerrera, Montalbano, De Carlos, et al., 2012; Alsafy, Bassuoni, & Hanafy, 2018; Amato et al., 2012; Dos Santos, Arantes, Santiago, & Dos Santos, 2015; El Bakary, 2014; Elgendy, Alsafy, & Tanekhy, 2016; Germanà et al., 2009; Guerrera et al., 2015; Ikpegbu, Ibe, & Nlebedum, 2019; Kasumyan, 2019; Kettratad, Senarat, Boonyoung, & Jiraungkoorsku, 2017; Levanti et al., 2017; Mahmoud, Essa, & Sayed, 2016; Sadeghinezhad, Rahmati‐holasoo, Fayyaz, & Zargar, 2015; Sayed, Mahmoud, & Essa, 2019; Yu et al., 2019). Several significant papers, important as comparative data, are present in the literature in upper vertebrates like birds, reptiles and mammals (Abbate et al, 2008, 2009, 2010, 2020b; Abumandour & Kandyel, 2020; Barbosa et al., 2020; Bels et al., 2020; Cizek, Hamouzova, Goździewska‐Harłajczuk, Klećkowska‐Nawrot, & Kvapil, 2020; Cizek, Hamouzova, Kvapil, & Kyllar, 2019; Emura, 2016a,2016b,2016c,2017,2018a,2018b,2018c,2018d,2019; Erdoğan & Alan, 2012; Erdoğan & Iwasaki, 2014; Erdoğan Lima & Pérez, 2016; Erdoğan Villar Arias & Pérez, 2016; Erdoğan, Villar Arias, et al., 2016; Erdoğan et al., 2018a; Erdoğan and Sağsöz, 2018b; Freire et al., 2019; Gonçalves et al., …”

Food transport in Reptilia: a comparative viewpoint

“…Finally, water is accumulated in the pharyngeal cavity corresponding to a final compartment and variously swallowed in separate phases (e.g. emersion phase; pharyngeal scope) [26,48]. In hummingbirds, special internal structures are able to move the nectar from the tongue to the buccal cavity by wringing (i.e.…”