الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Four experiments were carried out on 2940 yellow perch at Ohio Aquaculture Research Center and Aquaculture Genetics and Breeding Laboratory, The Ohio State University, USA to explore the effect of different temperatures, handling, salt treatment, air exposure stress and probiotic on their physiological and molecular stress, oxidative stress and growth responses.The first experiment was carried out on 960 Yellow perch (48 ± 10 g) which were subjected to handling stress and salt treatments at different temperatures to determine the physiological and molecular changes associated with the environmental changes. Yellow Perch were divided into three groups with four replicates and subjected to water temperatures 14, 20, and 26ºC. Handling was performed, in addition to a salt treatment at salinity of 5 ppt for each of the fish groups. Plasma samples were taken periodically for plasma cortisol concentration analysis and cortisol was used as a stress indicator. The most important response was an increase in plasma cortisol after handling for all groups, but lowest level of plasma cortisol was in fish subjected to 20ºC water temperature. To test the stressor effects on the molecular level, the transcriptional expression of stress biomarkers, including heat shock protein 70 (HSP-70), Insulin like growth factor-1 (IGF-1), and three antioxidant enzymes (glutathione peroxidase, GPx; Superoxide Dismutase, SOD; Cytochrome oxidase subunit I, COI), were studied using quantitative real-time PCR on mRNA extracted from liver of Yellow Perch. Handling stress caused a significant down-regulation (P ≤ 0.05) in HSP-70 at water temperature of 20ºC and up-regulation at 14 and 26ºC. IGF-1 was significantly up-regulated at 20ºC and down-regulated at 14 and 26ºC. GPx showed down-regulation at 14 and 20ºC, while up-regulation occurred at 26ºC, and SOD and COI were up-regulated at 14 and 26ºC and down-regulated at 20ºC. Salt treatment had a transient reverse effect on HSP-70, IGF-I, GPx, SOD, and COI since it caused decrease in gene regulation in all groups after three days from treatment, then elevated the regulation after six days, compared to the control groups among all temperatures. There was a regulatory link between HSP-70 and IGF-I expression level. Overall, our findings suggested that plasma cortisol; HSP-70, IGF-1, and antioxidant systems of yellow perch were affected by handling, temperature, and salt treatment. Information on the genes associated with various stressors in this species could provide important new insights into the stress responses that affect fish survival in aquaculture and the recreational fisheries industry. Identified stress biomarkers could be used to monitor the environment.In the second experiment, In this study, the effects of commercial probiotics Fishery PrimeTM administration on physiological and molecular stress responses of 1620 yellow perch, (2.5 ± 0.7 g) . Fish were divided into three groups, each having three subgroups, and subjected to water temperatures of 14, 20, and 26ºC. Yellow perch larvae subgroups were received water soluble commercial probiotics for 45 days and the second subgroups were reared without probiotic then subjected to air exposure stress while the third subgroups which didn’t receive probiotics or exposed to stress were served as controls along the experiment. Plasma samples were taken periodically for plasma cortisol concentration analysis and cortisol was used as a stress indicator. The most important response was an increase in plasma cortisol after air exposure for all groups, but lowest level of plasma cortisol was in fish subjected to 20 ºC water temperature with significant decline effect at probiotic-treated subgroups. mRNA levels of genes involved in stress response including heat shock protein 70 (HSP-70), Insulin like growth factor-1 (IGF-1), and oxidative stress related enzymes (glutathione peroxidase, GPx; Superoxide Dismutase, SOD; Cytochrome oxidase subunit I, COI) were quantified by RT-qPCR. A significant decrease of biomarkers related to stress and oxidative stress (HSP-70, GPx, SOD, COI) were observed in liver from the probiotic-treated fish compared with the control fish post air exposure stressor especially at water temperature 20 °C. In addition, an increase in the abundance of IGF-I gene was observed in the liver of the probiotic-fed fish. The mortality rates post air exposure stress were the highest at stressed groups without probiotics compared with probiotic-treated ones. Overall, the results show that probiotic administration may enhance yellow perch welfare by modulating and improving hepatic stress tolerance toward various aquaculture stressors.The third experiment was designed to study a commercial probiotic Fishery PrimeTM, acting as water soluble probiotic which was administered to 180 Yellow Perch (6.17 ± 2.27 g) for 6 weeks. The probiotic effect on growth and growth regulated genes were evaluated with respect to fish group fed on commercial feed (control group). Measures of body weight were performed to assess the growth performance. In addition, the expression of two related and highly indicative candidate genes involved in growth (Insulin-Like Growth Factor-I, IGF-I, and Growth Hormone, GH) were quantified through real-time PCR. Fish received the probiotic exhibited higher growth performance than control group at significance level (p < 0.05). Up regulation of GH and IGF-I transcriptions were observed in fish group received with probiotic which revealed higher levels than the control. The results confirmed the positive correlation between growth performance, GH and IGF-I mRNA gene expression in both probiotic treated and control groups. In conclusion, probiotic during early developmental stages can confer maximum beneficial effects resulting in magnitude increase in survivorship.The fourth experiment was to determine the effect of water soluble commercial probiotic on the transcriptional analysis of the anti-oxidative status of 180 yellow perch. Glutathione peroxidase (GPx), superoxide dismutase (SOD), and cytochrome oxidase subunit I (COI) were analyzed in yellow perch at 25 and 50 days after receiving the probiotic with respect to the control group by real time quantitative polymerase chain reaction. Two yellow perch groups fed on commercial feed: group one, received the probiotic in the water and the control group without probiotic addition. The group received the probiotic revealed lower expression levels of GPx, SOD and COI compared to the control group at 25 and 50 days. In our work the differences in gene expression patterns could only be attributed to the presence of probiotic, assuming a possible involvement of probiotic in the modulation of the antioxidant system in the fish. This study can conclude that among probiotic beneficial effects, it also could provide protection against oxidative stress and the ability to decline the risk of accumulation of reactive oxygen metabolites which are harmful to the host.