不同鈣環境對吳郭魚仔於鈣離子平衡之影響

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Title:	不同鈣環境對吳郭魚仔於鈣離子平衡之影響
Other Titles:	Effect of Enviormental Calcium Levels on Calaium Balance in Tilapia(Oreochromis mossambicus) Larvae
Authors:	周銘翊 Chou, Ming-yi
Contributors:	林惠真 Lin, Hui-Chen 東海大學生命科學系
Keywords:	鈣離子平衡;鈣離子流入速率;鈣離子流出速率 Calcium balance;Calcium influx;Calcium efflux
Date:	1999
Issue Date:	2011-06-15T03:40:25Z (UTC)
Abstract:	中文摘要鈣離子對於仔魚發育過程非常重要。過去對仔魚鈣離子平衡的研究中，因為測量技術上的困難，因此研究只著重在仔魚對鈣離子流入速率的討論。本實驗以不同鈣濃度處理當作環境因子，來探討仔魚鈣離子平衡的機制，並且也建立測量單一仔魚鈣離子流出速率的技術。將受精後48小時的吳郭魚受精卵，分別置於充足鈣（1 mM）及低鈣（0.02 mM）人工水中，在仔魚孵化後第0、3、6天時測量仔魚鈣離子流入及流出速率。結果發現低鈣處理組的仔魚在孵化後0天及3天，其鈣離子流入速率顯著低於充足鈣處理組;此差異持續到孵化後6天才消失。低鈣處理組的仔魚之鈣離子流出速率，在孵化後0天（24小時內）就顯著低於充足鈣處理組;表示流出速率的調節較流入速率的調節快。在短期適應實驗方面，將原馴養0.2 mM鈣濃度人工水之0天及3天大的仔魚分別置於充足鈣及低鈣人工水中，在不同時間對仔魚做鈣離子流入及流出測定。結果發現，0天大的仔魚其鈣離子流出速率在處理44小時後，顯著低於充足鈣組，而鈣離子流入速率在處理68小時後仍然低於充足鈣組。3天大的仔魚其鈣離子流出速率在處理22小時後，即顯著低於充足鈣組，而鈣離子流入速率則在處理39小時後，才與充足鈣組沒有差異;表示3天的仔魚，其鈣離子平衡調節能力比0天大的仔魚好。鈣離子含量方面，低鈣處理組的鈣含量，在實驗的7天時間，都顯著低於充足鈣處理組。本實驗發現，不同的適應時間及不同發育時期的仔魚，其對鈣離子平衡的調節能力不同。在發育初期，仔魚的鈣離子流入速率遽增，而流出速率則維持平穩，因此鈣離子流入速率對於仔魚體內鈣含量的累積之影響，較鈣離子流出速率重要。而降低鈣離子流出速率的速度比增加鈣離子流入速率快。3天大的仔魚，其鈣離子調節能力比0天大的仔魚好。此外，仔魚降低鈣離子流出速率以及增加流入速率，可能是為了補償在低鈣環境下體內鈣含量的不足。 Abstract Calcium ion is essential to larvae development and growth. Most of previous studies on calcium balance examined only the calcium influx and it was assumed that calcium efflux remained minimal. No comparison was done in terms of the rates of modulation between influx and efflux. This was, in part, because the technical difficulty in measuring calcium efflux in fish larvae. The present study, using different calcium concentration as environmental factors, investigated the calcium balance mechanism in developing tilipia larvae. In addition, the methodology for calcium efflux in tilapia larvae was established. Upon 48 hours after fertilization, eggs were incubated respectively in sufficient- and low-calcium (1 mM and 0.02 mM) artificial water. Calcium influx was measured on days 0, 3, and 6 after hatching. Larvae in low-calcium water had lower calcium influx from day 0 to day 3 after hatching. After 6 days of exposure, the low-calcium larvae had a similar influx as the sufficient-calcium larvae. Efflux was decreased from day 0 to day 6 after hatching. In the challenge experiment, fertilized eggs were incubated in normal calcium concentration ([Ca2+]=0.2 mM) medium and transferred to sufficient- and low-calcium artificial water 0 or 3 days after hatching. In 0-day-old larvae from low-calcium medium, efflux decreased after 44 hours of exposure, while influx increased to the level of the sufficient-calcium level after 68 hours of exposure. 3-day-old larvae from low-calcium condition decreased efflux after 22 hours of exposure, and influx increased after 39 hours. The calcium content in low-calcium larvae was lower than that in sufficient-calcium larvae throughout the experiment. My study indicated that the abilities to modulate calcium influx and efflux in larvae varied with different acclimation periods and developmental stages. Calcium influx in tilapia larvae increased rapidly in development period. Calcium efflux remained stable, and much lower than calcium influx. The calcium content in larvae accumulated rapidly during the development period. Compared to calcium efflux, calcium influx plays a major role in calcium content accumulation during the early development period. It took less time to decrease efflux than to increase influx. 3-day-old larvae have the better ability to calcium modulation. Increasing influx and decreasing efflux is a compensation for less calcium content in the larvae adapted to low-calcium environment.
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