Detailed morphological study of the tongue of forest dragon (Gonocephalus chamaeleontinus) by scanning electron and light microscopy

Abstract

Background: The forest dragon (Gonocephalus chamaeleontinus) is a reptile of the Agamidae family, and its distribution includes Indonesia and Malaysia. The forest dragon uses its tongue to catch insects and invertebrates. In terms of morphology, the tongue of the Agamidae family is different from other reptiles. The study of morphology in the tongues of Agamidae is crucial for understanding their feeding behavior, prey capture mechanisms, and evolutionary relationships.

Aim: This research attempts to analyze the morphology of the dorsal surface of the tongue of G. chamaeleontinus by using the scanning electron microscope (SEM) and its histological structure by using hematoxylin-eosin (HE) staining.

Methods: This study achieves the SEM and light microscope images using hematoxylin eosin stains and employs six samples of G. chamaeleontinus.

Results: The tongue of G. chamaeleontinus separated into three distinct parts: the apex (A), corpus (C), and radix ®. The structure's A contains dome-shaped papillae (DP). The C section contains DP and circumvallate papillae. The R contains scale-like papillae. Additionally, histological analysis using HE stains revealed the taste buds on the DP and circumvallate papillae and the presence of lingual salivary glands (SG) on the lamina propria mucosa.

Conclusion: The tongue's papillae of G. chamaeleontinus comprise sensory and mechanic papillae, which are also completed by lingual SG.

Keywords: Gonocephalus chamaeleontinus; Light microscopy; Scanning electron microscopy; Tongue.

Fig. 1.. Macroscopic view of G. chamaeleontinus tongue (a) in dorsal section (A = apex region, C = corpus region, R = radix region, BT = bifurcatio tongue, GL = glottis, Tr = trachea, CB I = ceratobranchial I, CB II = ceratobranchial II, CH = ceratohyal); (b) in lateral section (BT= bifurcatio tongue).

Fig. 2.. SEM image of G. chamaeleontinus tongue at the A. (a) whole A with 30 times magnification; (b) the anterior tip of the tongue shows bifurcatio tongue (BT), TP, and interpapillary groove (*) with 100 times magnification; (c) DP are polygonal with 100 times magnification; (d) at the superficial papillae there are TP with 400 times magnification.

Fig. 3.. SEM image of G. chamaeleontinus tongue at the C. (a) whole C with 30 times magnification; (b) polygonal DP with 100 times magnification; (c) on the superficial papillae there are CVP with 400 times magnification; and (d) and (TP and white circles) with 1000 times magnification.

Fig. 4.. SEM image of G. chamaeleontinus tongue at the R. (a) whole R with 30 times magnification; (b) SP with 100 times magnification, not all papillae on the R found TP (arrow).

Fig. 5.. Histological structure of the tongue of G. chamaeleontinus with HE staining of the A. (a) whole A visible DP; (b) distribution of lingual SG in the mucosal LP to the tunica MU; (c) tunica mucosa composed of LEM and mucosal LP; (d) lingual SG between the m. DL; (e) the ventral A shows m. T, two bundles of m. HG; and (f) entoglossal process of hyoid (EH).

Fig. 6.. Histological structure of the tongue of a G. chamaeleontinus with HE staining of the C. (a) whole C visible tunica MU consists of m. DL, m. T, m. verticalis (V), two bundles of m. HG, and m. GGL ventrally; (b) C dorsally showing DP, lingual SG distribution, LEM, mucosal LP, and tunica MU; (c) TB on LEM; (d) lingual SG between the m. DL; (e) entoglossal process of hyoid (EH) composed of (f) HC enveloped by PE.

Fig. 7.. Histological structure of the tongue of G. chamaeleontinus with HE staining of the R. (a) whole R visible tunica MU consisting of m. T, m. verticalis (V), two bundles of m. HG, and m. GGL in the ventral; (b) R dorsolateral part showed LEM, lamina LP, and tunica MU; (c) little m. DL; (d) R dorsal midline found (e) lingual SG; (f,g) lingual SG R located between m. T; (h) entoglossal process of hyoid (EH) composed of (i) HC enveloped by PE.