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This study was attempted to reveal the changes in three hematological parameters such as blood hemoglobin, number of white blood cells (WBCs) and number of red blood cells (RBCs) and one biochemical (e.g., glucose) parameter along with the changes in histomorphological structures of gills and kidney of Nile tilapia fry reared in saline water. Two experimental set up were used for two different age groups- 5 days-after-hatch (5DAH) and 15 days-after-hatch (15DAH) - to test a novel hypothesis: if a little difference in the age during the first exposure to saline water could produce any variation in the results. They were placed into 6 plastic drums having six different salinity levels: 0, 5, 10, 15, 20 and 25. After 60 days, at least 5 individuals were taken out from each drum to observe the above-hematological and histomorphological parameters. A two-way-ANOVA revealed that, except for hemoglobin, all the observed parameters have been affected the effect of age × salinity interaction (P<0.05). Between the two age groups, only the overall average glucose value and RBC count were significantly different. Among various salinity levels, only RBC and WBC counts differed significantly. Further, the mean glucose value, RBC counts and WBC count at different salinities differed significantly from the base mean value of each parameter. With regard to the histomorphological structure of the gills and kidney, various malformations were evident. Though hypertrophy, epithelial uplifting and epithelial necrosis were present as gill degenerations, hyperplasia was prevalent across almost all salinity levels. On the other hand, glomerular necrosis, pyknotic nucleus, hyaline droplets degeneration, shrinking of the glomeruli, etc. were observed in kidney structures. By assisting to understand the effects of salinity stress, all these data on tilapia fry will help to determine the prospects and scope of culturing the species in high-salinity water.
Ali et al. (Sat,) studied this question.