Histology and Histochemistry of the Digestive Tract of Transverse-bar Barb, Hampala macrolepidota Kuhl & Van Hasselt, 1823

บทคัดย่อ

Hampala macrolepidota is an important local fishery species; the information on its anatomy and microanatomy is scarce. Therefore, the histology and histochemistry of its digestive tract were systematically investigated. The digestive tracts of adult fish were removed and processed using the paraffin technique. Sections of 5 µm thickness were stained with hematoxylin and eosin (H&E), periodic acid-Schiff’s (PAS), and alcian blue (AB), pH 2.5 and pH 1.0. Its digestive tract consisted of the oropharynx, esophagus, and intestine, with no stomach observed. The stratified epithelium of the oropharynx was weakly positive-stained with PAS and AB at pH 2.5 and pH 1.0. In contrast, in the esophagus, mucous and goblet cells were strongly positively stained with all stains, indicating the secretion of neutral mucin and carboxylated and sulfated acid mucins. The intestine can be divided into three regions: anterior, middle, and posterior. Meanwhile, the enterocytes were positively stained with PAS; however, the goblet cells were positively stained with PAS at pH 2.5 and pH 1.0. The goblet cells secreted neutral mucins, as well as carboxylated and sulfated acidic mucins. The middle intestine showed crypt-like glands and the highest histometric values, indicating that it served as the main site of digestion and nutrient absorption, despite the absence of a stomach. The muscular layer varied regionally, with skeletal muscle in the oropharynx and esophagus and smooth muscle in the intestine. The intestinal coefficient was 0.69, indicating that it was a carnivorous fish. These findings provided fundamental data relevant to aquaculture, ecology, and comparative vertebrate anatomy.