Digestive tract morphology and argyrophil cell distribution of three sympatric lizard species

The digestive tract plays a crucial role in an organism's health. Here, the digestive tract morphology and argyrophil cell distribution of three sympatric lizard species, Teratoscincus roborowskii, Phrynocephalus axillaris and Eremias roborowskii, were studied. Our results show that T. roborowskii's snout–vent length (SVL) and digestive tract length (DTL) were significantly longer than those of P. axillaris and E. roborowskii. P. axillaris' relative intestine length was 1.25, which was significantly longer than those of the other two species. The three lizard species' digestive tract structures were generally similar, whereas their histologic characteristics exhibited significant differences. Particularly, T. roborowskii's and P. axillaris' esophagus mucosa was pseudostratified ciliated columnar epithelium, whereas simple columnar epithelium was observed in E. roborowskii, which also had fewer mucosal folds than the other two species. In all three lizard species, the small intestines' mucosal lining consisted of simple columnar epithelium with many goblet cells; the largest quantity of villi was found in T. roborowskii. Moreover, T. roborowskii's mucous membrane (MM) and tunica muscularis (TM) were obviously thicker than those of the other two species. However, the argyrophil cells' distribution densities of the three species were remarkably different; such differences were highest in the cardia of T. roborowskii and E. roborowskii, but P. axillaris was observed to have more argyrophil cells in its stomach body. Our results indicated that the three lizards' different histomorphologies might be due to limited food resources, availability of a single food type in the Turpan Basin's extremely arid and hot environment, as well as T. roborowskii's special frugivorous behavior. Morphological studies of these lizards are necessary to understand their digestive systems' structure and operation, as well as to facilitate physiological studies of adaptions to extreme desert habitats.