Fig. 6

Light microscopy micrographs of the foregut of Lepidobatrachus spp. a. L. llanensis. Section of the esophagus with ciliated cells and numerous goblet cells forming the lining epithelium in an early limb bud larval stage. b. L. llanensis. Sections of the transitional zone from the esophagus to middle stomach showing gastric glands and the submucosa layer thickened in at the end of larval period. c. L. llanensis. Section from the middle of the stomach showing different types of glandular cells, and mucous glands already differentiated (PAS-positive) in the fundic region in tadpoles at an early limb bud larval stage. d. L. llanensis. Section of the middle stomach exhibiting increment of folds, gastric glands, the connective tissue in the submucosa and outer circular muscular layer thickened at the end of larval period. e. L. laevis. Section of the fundic region displaying simple tubular gastric glands formed by mucous neck cells at the upper portion of the gland and oxynticopeptic cells (*) at the lower portion in an advanced tadpole stage without vent tube. The staining is PAS and AB combined. f. L. llanensis. Section of the fundic region with granular material of oxynticopeptic cells (*) revealed by Masson’s trichrome method at the end of larval period. g. L. llanensis. Section at the level of the pyloric region with a remarkable thickness of circular muscles in the muscular layer in an early limb bud larval stage. h. L. llanensis. Section at the level of pyloric region denotes the increment in the thickness of the wall of the gut at the end of larval period. Abbreviations: Ec: epithelial cells; Gc: goblets cell; Gg: gastric glands; Gp: gastric pits; Me: muscularis externa; mnc: mucous neck cells; Sm: submucosa