碩士 / 國立中山大學 / 海洋科學系研究所 / 104 / In present aquaculture, the intensive and recirculating aquaculture systems are universally used. Ammonia is a common toxic substance in aquatic environments, which is excreted by aquatic animals as a by-product of protein catabolism and from the decomposition of feeds and organic matter. Therefore, it can easily rise to high levels to harm to aquatic animals in short-term time. Moreover, excessive ammonia would cause the animals can''t maintain physiological homeostasis to eventually lead to death. Pacific white shrimp (Litopenaeus vannamei) is an important worldwide aquaculture species. However, study on the mechanisms of molecular and cellular stress responses employed for coping with sublethal ammonia stress remains limited. In this study, regulatory responses of protein quality control (PQC), antioxidative mechanisms and apoptosis were investigated in shrimp gills after 96h exposure to sublethal ammonia levels (1.5 and 3 mg/L TAN). In PQC mechanism, the study concluded that Heat shock factor 1 (HSF1) and Heat shock protein (HSP70) the mRNA expression in gills and hemocytes compared to the control group had significantly increased. In addition, protein aggregation results in each category no significant differences. Moreover, the transcript levels of antioxidative enzymes, manganese superoxide dismutase (Mn SOD), glutathione peroxidase (GPx) and catalase in gills evidently upregulated at 3 mg/L TAN exposure. In the results of hemocytes, the amount of Mn SOD mRNA expression compared to the treatment group, there was a downward trend, GPx and CAT mRNA expression of the amount of gill tissue has the same tendency, under exposure to 3 mg / L are significant increase. However, in gills and hemocytes no significant difference was found in total antioxidant capacity among all groups, possibly implying the antioxidative enzymes acted a predominant role in antioxidant cytoprotection in white shrimp under ammonia stress. In addition, the results from apoptotic responses revealed that transcript levels of caspase-3, -4 and -5 increased in gills as well as extensive DNA fragmentation was induced obviously in shrimp gills exposed to 3 mg/L TAN. However, in hemocytes experiment, four genes of Caspase-2, -3, -4 and -5mRNA in the 3 mg / L of ammonia exposure under rising trend. The control group with no significant differences in the DNA fragment of the experimental results. This study improved the understandings of vital cytoprotective roles of PQC, antioxidative defenece and apoptosis in coping with sublethal ammonia stress in gills and hemocytes of white shrimp. These findings were suggested to be helpful in predicting sublethal ammonia toxicity and potentially useful in environmental monitoring studies.
| Identifer | oai:union.ndltd.org:TW/104NSYS5276020 |
| Date | January 2016 |
| Creators | Chao-Yi Lee, 李朝意 |
| Contributors | Cheng-Hao Tang, Li-Lian Liu, 湯政豪, 劉莉蓮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 50 |
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