Fig. 4

Light microscopy micrographs of the foregut of Chacophrys pierottii. a. Section of the esophagus in an advanced larval stage (Stage 39) shows a thin mucosa with ciliated cells and columnar mucous cells (PAS-positive). b and c. Panoramic and detailed sections of the esophagus in a froglet showing folds of mucosa lined by a ciliated epithelium with numerous goblet cells. d and e. Panoramic and detailed sections of the larval “stomach” (i.e. the maniccotto glandulare) exhibit the fundic region with numerous gastric glands and some goblet cells (PAS-positive) in an advanced larval stage (Stage 39). f. Middle stomach section with folded mucosa and numerous gastric glands with different types of glandular cells in the froglet. g. Amplification of F-image showing gastric glands with mucous neck cells (PAS-positive) at the upper portion and oxynticopeptic cells (*) at the lower portion. h. Section at the level of the pyloric region there are small simple tubular gastric glands in the froglet. Abbreviations: Ec: epithelial cells; Gc: goblets cell; Gg: gastric glands; Gp: gastric pits; Me: muscularis externa; Mm: muscularis mucosa; Mnc: mucous neck cells; Sm: submucosa