Phrynops geoffroanus is the omnivorous chelonian with widest geographical distribution in South America. This work describes the histology and histochemistry of the digestive tube of this species, to relate the characteristics of these organs to the species' eating habit. The esophagus, stomach and intestine of four specimens were fixed in 10% formal and embedded in paraffin by routine histological techniques. Afterwards, 5-µm sections were stained with hematoxylin-eosin (HE), periodic acid-Schiff (PAS) and alcian blue (AB) pH 0.4 and 2.5. The tube is formed by the mucosa, submucosa, muscular and adventitia or serosa layers. The mucosa layer of the esophagus and stomach is lined with a simple cylindrical epithelium with mucus-secreting cells, where are intraepithelial glands inserted in the portion of the esophagus and gastric fossettes emptying into glands in the stomach. The stomach is divided into an anterior, middle and posterior region, according to the depth of the fossettes and the concentration of gastric glands. The intestine is lined by a simple cylindrical epithelium with striated boundaries and goblet cells and is divided into an anterior and posterior regions, according to the pattern of folds of the mucosa layer and the number of goblet cells. Reactivity to PAS and AB is observed in the entire tube. Smooth muscle fibers are present in mucosa layer of all the segments. The muscular layer is formed by two sub-layers of smooth muscle, except for the posterior stomach. This study will help understanding of the digestive physiology of P. geoffroanus and provide data for comparative analyzes with other turtles.
Reptile; esophagus; stomach; intestine; mucous-secreting cells
