Document Type : Research Paper
Authors
1
Persian Gulf University
2
Persian Gulf Research Institute, Persian Gulf University,
3
2- Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
10.22124/japb.2024.27017.1535
Abstract
When fish are exposed to environmental stress, anatomical and physiological changes occur in their bodies, and if these changes are not corrected or compensated, the body becomes weak and loses its ability to deal with other stressful factors. Therefore, this study aims to investigate the effects of different salinities without adaptation on blood electrolytes and the structure of gill and kidney tissues in Asian seabass (Lates calcarifer). After a 14-day acclimation period with feed and experimental condition, a number of 180 Asian seabass fry with an average initial weight of 34±1g (mean±SD) and without adaptation with different salinities of water were randomly selected and distributed in 12 tanks with a volume of 300 liters of water and a density of 15 fish per each tank. To conduct the experiment, 4 treatments each with 3 replications including treatment 1 (fresh water, salinity of 0 g/L), treatment 2 (treatment with salinity of 15 g/L), treatment 3 (treatment with salinity of 35 g/L) and treatment 4 (treatment with salinity of 50 g/L) were considered. The length of the trial period was 120 hours (5 days) and the fish were fed twice daily to apparent satiation. The desired salinities were obtained by diluting sea water (50 ppt) with fresh water. The average water temperature was 27±1°C. The sampling of fish was done at 6, 24, 72 and 120 hours. No mortalities were observed during the experimental period. The results of the present study showed that different salinities without adaptation in the amount of osmolality, sodium, potassium and chlorine ions in the blood of Asian seabass fish cause significantly changes in different hours of the experiment (P<0/05). Lesions such as epithelial necrosis and adhesion of lamellae were observed in the gill tissue of the 0, 15 and 35 g salinity/L groups than the 50 g salinity/L group. Also, in the kidney tissue of the 0, 15 and 35 g salinity/L groups, lesions such as an increase in the concentration of melano-macrophages, an enlargement of Bowman's capsule, an increase in the space in the center of the glomerulus, and necrotic cells in the hematopoietic tissue were observed compared to the 50 g salinity/L group. The highest amount of gill and kidney tissue damage in this fish belonged to the 0 g salinity/L group and the lowest amount belonged to the 50 g salinity/L group. The results showed that different salinities without adaptation can change blood electrolytes and the structure of gill and kidney tissues in Asian seabass.
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