Morfohistologia Do Trato Digestório Da Espécie Pseudotylosurus Microps (Gunther, 1866) (Osteichthyes; Belonidae) Na Bacia Do Rio Tocantins

Abstract

Pseudotylosurus microps is a medium-sized species commonly known as needlefish. It is

distributed in the Amazon and Paraná River basins. This piscivorous species lacks a well- defined stomach, is solitary, and swift, exhibiting epipelagic habits. The objective of this study

was to describe the anatomy and histology of the digestive tract, aiming to contribute to the understanding of its morphology and function. The external and internal morphology of the digestive tract was observed, including the position of the mouth, oral dentition, tongue, pharynx, gill arches, stomach shape, esophagus, and intestines. Histological characterization was achieved using hematoxylin and eosin-stained histological sections. The results revealed that the digestive system of P. microps is a hollow tube composed of the esophagus and intestine, without a well-defined stomach. The esophagus is lined with stratified squamous epithelium and a muscular layer that extends throughout its length. The morphohistology of the intestine differs in the middle and posterior parts. In the middle section, four layers—mucosa, submucosa, muscular, and serosa—were observed, along with gland-like structures resembling Lieberkühn's crypts and villi lined with simple columnar epithelium, featuring goblet cells and microvilli. The posterior intestine (rectum) consists of columnar epithelium with a higher abundance of goblet cells. The digestive tract of P. microps aligns with its piscivorous feeding habits, displaying histological features that reflect adaptation to the absence of a stomach.