Effect of Food Deprivation on Plasma Cortisol, Carbohydrate Metabolism, and Histomorphology in Clarias batrachus.

The nutritional status of fish is essential for its health, experimental studies, and aquaculture practices. The current study investigated the impact of food deprivation on biochemical parameters, histology of skin, gill, and kidney tissues, and ultrastructure of gills in Clarias batrachus. Fish were subjected to food deprivation for 2, 7, and 15 days resulting in (a) significant increase in plasma cortisol levels, (b) no significant changes in plasma osmolality and plasma glucose content, and (c) significant decrease in liver and muscle glycogen contents. A substantial damage was detected in skin, gill, and kidney tissues with histological alterations in a time-dependent manner. Skin tissue displayed melanomacrophage aggregation, excoriated epidermis and dermis. In gill tissue, epithelial lifting, edema, desquamation, deformed secondary lamellae, and lamellar hyperplasia were observed. Kidney tissue exhibited degenerated tubules, melanomacrophage aggregations, and shrunken renal tubule. Scanning electron microscopy revealed that food deprivation-induced marked presence of mucus, chloride cells, and pavement cells with well-defined microridges and microbridges following 2 days, opening of chloride cells was more prominent after 7 days, while more mucus secretion was observed after 15 days. After food deprivation, alterations in biochemical and histological parameters, and ultrastructural changes in target tissues reflect physiological and morphological disturbances in fish. The novelty of this study is that these parameters can be considered as biomarkers of feeding stress in fish and fish health and can provide important insights for better aquaculture practices.