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標題: | 鹽度刺激對點帶石斑稚魚滲透壓調節及能量代謝影響之研究 Effects of Salinity Shock on Osmoregulation and Energy Metabolism of Orange-spotted Grouper Juveniles ,Epinephelus coioides |
作者: | 朱永桐 |
出版年 : | 1999 |
學位: | 碩士 |
摘要: | 生物藉著生理機制之調適及行為上的反應來適應環境。石斑魚屬於廣鹽性 (Euryhaline)魚類,其適合生存成長的鹽度範圍為 11- 41 ppt ,顯示出其有相當大的調適能力,使魚體內部維持衡定而得以存活成長。本研究以急劇的鹽度刺激(salinitv shock)方式來探討不同鹽度刺激對點帶石斑(Epinephelus coioides)之生理影響,包括滲透壓調節(osmoregulation)及醣類代謝(carbohydrate metabolism)兩個部份。 馴化於25 ppt 之石斑魚,分別移入不同的鹽度 5 、 15 、 25 、 35 、 45 ppt ,進行刺激試驗,探討其在急劇鹽度變化下的滲透壓調節情形,包括血容比、血紅素、滲透壓、鈉、鉀、鈣、鎂、氯離子、及鰓絲 Na + , K +- ATPase 的變化。在血液中血容比及血紅素含量上並無明顯變化。血漿中滲透壓值於低張環境下(5、15ppt)其滲透壓值會出現暫時性低滲透壓現象( hypoosmorality ) ,然後於 6 小時以後則回復初始值,相反的,於高張環境下( 35 、 45 ppt ) ,則出現暫時性高滲透壓現象( hyperosomorality ) ,於 12 小時以後,再調降為原來滲透壓值。氯離子變化與滲透壓值變化大致相同,即進入低鹽或高鹽環境,分別出現低氯( hypochloride )及高氯( hyperchloride )現象,而後再回復至原來之離子濃度。血漿中鈉離子在低鹽下會出現暫時性低鈉( hyposodium )現象,然而在 24 小時即已調回原來之離子濃度,在高鹽下鈉離子濃度於 24 小時才明顯上升,至 48 小時則尚未回復。鉀離子在高、低鹽刺激後則出現濃度低下現象。鈣及鎂離子則呈不規則性變化,以上之生理指標,均出現壓迫及調適之反應。另外鰓絲之 Na + , K +- ATPase 活性,在高鹽刺激後呈現高活性現象,在低鹽下似乎有抑制其活性之現象。 鹽度刺激會誘發石斑魚血糖急劇升高現象,而低鹽度(5ppt)刺激下之血糖量上升,僅出現在刺激早期,至於高鹽刺激下, 48 小時內均維持在高血糖( hyperglycemia ) 現象。說明瞭鹽度刺激,對石斑魚表現了明顯的壓迫反應及能量需求迫切性。血乳酸值在低鹽(5 ppt)及高鹽(35 、45 ppt)的刺激下, 0 . 5 小時其血漿中乳酸含量明顯上升,然後各處理組再隨著時間的進行而有下降的趨勢,代表在刺激初期以無氧代謝獲得能量之需求性。 關於鹽度對醣類代謝之影響探討,以 5 、 25 、 45 ppt 之鹽度處理之石斑魚肌肉及肝臟組織分析其代謝產物(metabolites)如肝醣(glycogen)乳酸(lactate)與醣類代謝過程中相關關鍵酵素如肝糖磷酸化?(phosphorfase a ) ,磷酸果糖激?(PFK) ,丙酮酸激?(PK ) ,檸檬酸合成?(CS ) ,乳酸去氫?(LDH ) ,及果糖雙磷酸?(FBPase)石斑魚在鹽度刺激下,肝臟組織中醣解酵素 PFK 、 PK 及醣質新生酵素 FBPase 活性均增加,其中 PFK 、 PK 促進提高醣解作用能力,主要是在提供魚體肝臟合成所需的受質及輔?,然復以乳酸、胺基酸、脂質等,經由醣質新生作用,合成魚體組織中所需要之葡萄糖,藉血液之運輸至各組織以供利用。 低鹽刺激下肌肉組織中葡萄糖來源有二:一藉由增加 phosphorylase a 之活性,自肌肉組織中分解肝醣而來,另一則由肝臟合成透過血液運送而來,然而高鹽刺激下其能量來源主要依賴血中葡萄糖。高、低鹽度刺激後肌肉組織能量需求增加,故 PFK 、 PK 等活性升高,再藉 CS 以有氧代謝獲取能量。另在高鹽刺激下 LDH 活性亦上升,造成肌肉乳酸堆積,顯示在高鹽之刺激下,其能量產生除了藉有氧代謝反應外,也由無氧代謝反應產生,這說明瞭在高鹽環境下之生理調適需耗費更多之能量。 Fish were able to adapt to the fluctuating environment by behavioral responses and physiological regulations. The groupers, euryhaline teleosts, were tolerable and survival to the wide salinity range, from 11 to 41 ppt. The approach of salinity shock was employed in this study to comprehend the physiological responses of the groupers, Epinephelus coioides, and specially focused on osmoregulation and carbohydrate metabolism. The acclimated groupers at the salinity of 25 ppt were directly transferred to varying salinities of 5, 15, 25, 35 and 45 ppt, and the osmoregulation of the groupers under the salinity shock was monitored. The parameters monitored included hematocrit, hemoglobin, plasma osmolarity and ion composition, and Na+-K+ -activated ATPase activity in the gills. Under hypoosomotic environment (5 and 15 ppt), hypoosmorality was characteristic responses in the initial phase of salinity shock, but the plasma osmolarity recovered to the normal level after 6hr. A temporary hyperosmorality was noted under hyperosmotic environments in the initial period up to 12 hr. Similar trends of the changes in the plasma chloride and sodium ion were observed, but a longer period of osmotic regulation, 24 hr, is necessary to return to the normal level of respective ions. Plasma potassium contents were depressed in both hypoosmotic and hyperosmotic environments, while changes in the plasma calcium and magnesium showed irregular patterns. Furthermore, Na+-K+ ATPase activity was elevated under hyperosmotic conditions, and vice versa. The physiological responses and regulation were demonstrated in these parameters monitored. Hyperglycemia was found to be a common indicator for stress response in the groupers exposed to varying salinities. Plasma glucose were elevated within 48 hr under hight salinity condition , and only in a short initial phase of low salinity conditions. The observation not only implied the occurrence of stress responses, but also increased demands for energy for physiological regulation and compensation. Hyperlactocemia was another indicator of the stress responses, and significant increase in the plasma lactate was detectable within 0.5 hr after the shock in all cases, followed by gradual declines thereafter. This suggested that the groupers rely heavily on the energy supplies through anaerobic pathway in the initial phase of physiological compensation. Influences of varying salinities on the carbohydrate metabolism were further examined and analyzed on the metabolites (glycogen and lactate) and enzymes involved in the carbohydrate metabolism in both hepatic and muscular tissues. The metabolic enzymes included phosphorylase a, phsphofructokinase (PFK), pyruvate kinase (PK), citrate synthase (CS), lactate dehydrogenase (LDH), fructose-1 ,6-biphosphatase (FBPase). Under the salinity shock, the activities of glycolytic enzymes (PFK, PK) and glyconeogenetic enzyme (FBPase) were all increased in the hepatic tissue, The former enhances the glycolysis to supply necessary substrate and co-enzymes, while the lactate, amino acids and lipids were converted to glucose via glyconeogenesis and the glucose produced are circulated to the tissues as the source of energy. In the muscular tissues, glucose was produced primarily from the catabolism of glycogen through phosphorylase a under hypoosmotic shock. In contrary, under the hyperosmotic conditions, glucose was supplied via circulatory system. The increased demands of energy under osmotic stress were met by activation of PFK and PK, and the efficient energy was obtained via aerobic pathway. However, under the hypersomotic conditions, elevation of LDH activities was evident. This implied that the energy was derived from both anaerobic and aerobic pathway, and further suggested the energy requirement for the osmoregulation in the hyperosmotic environments was much higher than those in the hypoosomotic conditions. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75017 |
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顯示於系所單位: | 漁業科學研究所 |
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