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.
Highlights
Morphological studies of the digestive tract of fish are considered effective tools for understanding the mechanisms of ingestion, digestion and absorption of food, and have recently been carried out for several species (Xiong et al 2011, Germano et al 2013, Løkka et al 2013)
Studies on the morphology of the digestive tract of fish have been conducted by several authors, from the classic works of Al-Hussaini (1949), Angelescu and Gneri (1949) and Bértin (1958), to the more recent ones which employed more refined techniques such as histochemistry and electron microscopy, for example those of Xiong et al (2011) and Løkka et al (2013)
According to Xiong et al (2011), Rodrigues and Menin (2005) there should be more researches on the processes of nutrients digestion, such as this paper that makes it possible to describe relevant information on the species, which is important for human feeding and professional fishing (Sato and Barbieri 1982, Barbosa and Soares 2009)
Summary
Morphological studies of the digestive tract of fish are considered effective tools for understanding the mechanisms of ingestion, digestion and absorption of food, and have recently been carried out for several species (Xiong et al 2011, Germano et al 2013, Løkka et al 2013). The digestive system of fish show distinctive morphological and functional diversity (Diaz et al 2003), due to the high biodiversity in teleost fish and the different positions they occupy in the food chain (Santos et al 2007). The oral and oropharyngeal cavities play important roles in selecting, seizing and directing food to the oesophagus
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