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Hematological and Osmotic Changes of Seabass, Lates calcarifer under Salinity Shock
金目鱸在鹽度刺激下血液因子與滲透壓之變化
摘要
金目鱸是台灣水產養殖產業中重要經濟魚種之一。本文之目的擬報導該魚種在急劇鹽度壓迫下之生理反應。試驗魚馴化在25ppt鹽度下兩週後，直接移入5或45ppt鹽度環境中，追蹤檢測血液及滲透壓因子之24小時變化。 依據金目鱸試驗過程中活存及生理調適狀況判斷，可確定該魚種在5至45ppt鹽度範圍內之可耐性，也可推論金目鱸在此鹽度範圍內蓄養之可能性。 血液滲透壓在24小時試驗期間，維持在相當穩定之範圍內（266.2與344.2mOsmkg^(-1)之間），但血液滲透壓是隨著環境鹽度之升高而呈現明顯上揚之現象，其中鈉與鎂離子之變化與血液滲透壓之增減呈正相關性，鉀離子則呈逆相關之現象。至於魚類生理調節中能量代謝狀態以耗氧量及血醣量表示。在兩種試驗鹽度下耗氧量及血醣量均有明顯的增加，血液氧氣攜帶容量亦有相同之變化。由此可知，金目鱸在變動鹽度下的生理調適充分表現在滲透壓調節，能量代謝及呼吸容量間等生理上，分別以血液滲透壓，耗氧量和血醣量，以及呼吸色素量表示。
並列摘要
The seabass, Lates calcarifer is one of the commercially important cultured species in Taiwan. The objective of this research is aimed to document the physiological responses of this species under acute salinity shock. Fish were acclimated at a salinity of 25ppt for 2 weeks and then transferred directly to salinity extremes of either 5 or 45ppt. Changes in physiological, hematological and osmotic parameters of the seabass were monitored for a 24-h period. The tolerability of the seabass to the salinities of 5ppt to 45ppt is clearly demonstrated by their survival and capabilities of physiological compensation. The possibility of the seabass being cultured in water bodies with a wide range of salinities is further confirmed. Marked increases in the plasma osmolality, corresponding to environmental salinities, were noted over the 24-h period, although the plasma osmolality of the seabass remained at a relatively stable level of 274.6~350mOsm kg^(-1). The parallel changes of osmotic components of Na(superscript +) and Mg(superscript +) with the blood osmolality were further noted, while the blood K(superscript +) concentrations were inversely decreased. The status of energy metabolism, indicated by the oxygen consumption and hyperglycemic responses are notably enhanced in both salinity extremes conditions. Similar changes in the respiratory constituents involved in oxygen-carrying capacity are further demonstrated. The present study indicated that the compensation process of the fish to altered environmental salinities is evidently reflected in the physiological processes of osmotic regulation, energy metabolism, and respiratory capacity indicated respectively by the blood osmolality and ion osmolarity, oxygen consumption and hyperglycemic responses, and respiratory pigments.