Morphological characteristics of the digestive tract of Schizodon knerii (Steindachner, 1875), (Characiformes: Anostomidae): An anatomical, histological and histochemical study

Abstract

The digestive tracts of 44 specimens of Schizodon knerii were studied using anatomical, histological and histochemical techniques. The mouth has terminal position, the lip epithelium is squamous stratified with mucous, claviform cells and taste buds, teeth have an incisive form and the tongue has a stratified squamous epithelium with mucous cells and taste buds. The oropharynx cavity is formed by gill apparatus and pharyngeal teeth. The oesophagus presented pleated mucosa, a stratified squamous epithelium with mucous cells, oesophageal glands and taste buds. The stomach presented cardiac, fundic and pyloric regions, simple prismatic epithelium with tubular glands, with none in the pyloric region. The intestine contains 11-15 pyloric caeca, a simple prismatic epithelium with brush border, goblet cells and lymphocytes. Mucosal cells, oesophageal glands and goblet cells reacted positively to PAS, amylase + PAS, Ab pH 2.5 and Ab pH 0.5. Gastric prismatic cells reacted positively to PAS, amylase + PAS, but only those in the pyloric region reacted positively to Ab pH 2.5 and Ab pH 0.5. The results improve the understanding of the anatomy of S. knerii feeding habits and the presence of mucosubstances in the epithelium, highlights the importance of glycoproteins for passing food through the digestive tract.

Morphological characterisation of the digestive tract of the catfish Lophiosilurus alexandri Steindachner, 1876 (Siluriformes, Pseudopimelodidae)

“…The latter two authors suggest that the different anatomical shapes of fish stomachs may be related to different eating habits, but the anatomical shape may well be related to phylogeny, as there are no conclusive studies. The stomachs of other fish have been divided into cardiac, fundic and pyloric regions, like that of pacamã (Cao & Wang, ; Raji & Norouzi, ; Santos, Arantes, Santiago et al., ). This anatomical division may be a characteristic of teleosts that have a true stomach and indicates the specialisation of regions of the stomach for gastric secretion, maceration, homogenisation and guidance of food.…”

“…The digestive tract of fish is a widely studied topic, from the classic works of Al‐Hussaini (); Angelescu and Gneri () to recent works, such as Germano et al. (); Santos, Arantes, Santiago, and Santos (), Santos, Arantes, Pessali, and Santos (); Fagundes, Rotundo, and Mari (); Andrade, Guimarães, Rotundo, and Mari (). These studies provide crucial information for the cultivation and conservation of species (Santos, Arantes, Santiago et al., ; Wilson & Castro, ).…”

“…(); Santos, Arantes, Santiago, and Santos (), Santos, Arantes, Pessali, and Santos (); Fagundes, Rotundo, and Mari (); Andrade, Guimarães, Rotundo, and Mari (). These studies provide crucial information for the cultivation and conservation of species (Santos, Arantes, Santiago et al., ; Wilson & Castro, ). Therefore, the aim of our work was to describe the anatomical and histological characteristics of the oesophagus, stomach, and intestine of the L. alexandri , relating these characteristics to its eating habits and expand their biological knowledge to improve conservation programmes.…”

Morpho-histological characterisation of the alimentary canal of an important food fish, Asian seabass (Lates calcarifer)

“…The requirement for higher level of protection provided by the multi-layered epithelium in typical fishes could perhaps be offset by the presence of numerous mucosal glands in the Asian seabass esophagus. This is since the secretion from these glands would be useful for protecting the mucosa from mechanical wear and aid the passage of food into the stomach lining (Santos et al, 2015b; Vegas-Velez, 1972). Further, the mucous secreting cells interspersed in the simple columnar epithelium help in safeguarding the lining of the esophagus from chemical and mechanical injury and also serve as a lubricant to aid in food passage (Machado et al, 2013).…”

“…The intestinal coefficient of Asian seabass is relatively low (1.1) and falls within the range expected for carnivorous fishes (0.2–2.5). On the other hand, the intestinal coefficient range for omnivorous (0.6–8.0) and herbivorous (0.8–15.0) fishes are much higher (Al-Hussaini, 1949; Angelescu & Gneri, 1949; Bertin, 1958; Santos et al, 2015a; Santos et al, 2015b; Xiong et al, 2011). The Asian seabass intestine can be divided into three regions—the anterior, mid and posterior portions at the histological level, though no morphological differences existed as is the case for most fishes (Gargiulo et al, 1998; Scocco, Menghi & Ceccarelli, 1997).…”