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

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

Histopathological changes in two potential indicator fish species from a hyper-eutrophic freshwater ecosystem in South Africa: a baseline study

Histopatholigical changes were identified in selected target organs from two freshwater fish species, Clarias gariepinus and Oreochromis mossambicus, inhabiting a hyper-eutrophic freshwater aquatic system. The approach was to use a histology-based fish health assessment protocol which included a semi-quantitative histopathological assessment of six target organs (gills, liver, ovaries, testes, kidney, and heart). Results of water quality analysis showed selected variables to be above the recommended levels including pH, ammonia, nitrogen, chloride, and phosphorus. A number of histopathological alterations were identified in the target organs of both species, with the highest number observed in the liver. Species differences were identified in terms of the severity of the alterations within all the organs, with most alterations being regressive in nature. The results of this study provide valuable baseline data for two indicator species inhabiting a hyper-eutrophic system that could be useful for future bio-monitoring studies.The National Research Foundation of South Africahttp://tandfonline.com/loi/taas2