This study describes anatomical, histological and histochemical features of the 
digestive tract mucosal layer of the matrinxã Brycon amazonicus, an omnivorous 
freshwater fish endemic from the Amazon basin. This species presents short thick 
oesophagus with longitudinal folds, that allow the passage of large food items. 
The mucosa is lined with a stratified secretory epithelium rich in goblet cells 
that secrete neutral and acid mucins. The two mucin types provide different 
viscosity in anterior and posterior oesophagus related to the protective and 
lubricant functions, respectively. The stomach is a highly distensible Y-shaped 
saccular organ. Here, it is proposed that this anatomical shape plays an 
essential role in food storage when food availability is abundant. The stomach 
mucosa is composed of epithelial cells with intense neutral mucin secretion to 
protects against gastric juice. The intestine is slightly coiled and presents 
internally a complex pattern of transversal folds that increases the absorption 
surface and the retention time of food. Goblet cells in the intestine secrete 
acid and neutral mucins that lubricate the epithelium and aid in the digestive 
processes. In the rectum, an increase in goblet cells population occurs that may 
be related to better lubrication.