ABSTRACT
Based on the nature of the food taken by fish, they are often divided into the following trophic types: herbivores and detritophages, omnivores, and carnivores. The gastrointestinal tract of the fish is the site, where, first of all, the digestion of food and absorption of nutrients take place. However, it also plays a role in modulating the immune response and gas exchange. The gastrointestinal tract can be divided into four sections considering its topography: headgut, foregut, midgut, and hindgut. The gastrointestinal tract of larvae is morphologically and functionally incompletely developed, compared to that of juvenile stages. It is histologically undifferentiated throughout its length. From the beginning of exogenous feeding, the gastrointestinal tract starts anatomical and histological differentiation.
This chapter discusses the anatomy and histology of the gastrointestinal tract of fish. The morphological and physiological adaptations of different fish species to digestion of food as well as gas exchange through the digestive tract are presented. Histology of different parts of the gastrointestinal tract are also described, indicating types of epithelial cells and functions they perform.
