|Abstract: ||研究曝露於酸性環境下之淡水長臂大蝦之1）耐受性，以及對其2）成長、脫殼和攝餌的影響，3）血淋巴酸-鹼平衡、滲透壓和離子調節的影響，及4）脫殼後期蝦之甲殼鈣化和離子吸收，以及組織離子調節的影響。 淡水長臂大蝦曝露於pH 3.6水中24 h全部死亡。24、48、72和96 h LC50的pH值分別為4.00、4.05、4.07和4.09，與淡水螯蝦和草蝦比較，淡水長臂大蝦對於酸性環境的耐受性較差。 淡水長臂大蝦曝露於pH 5.6水中42天，其體重與體長均顯著低於蝦曝露於pH 8.2者。42天及56天的EC50 pH值（影響增重為對照組一半的pH值）分別為5.61與6.25。淡水長臂大蝦曝露於pH 6.8環境中，其脫殼頻率與攝餌率均顯著下降，不影響脫殼與攝餌而可接受的最低pH值為7.4。 淡水長臂大蝦曝露於pH 4.4水中12 h，其血淋巴滲透壓、Cl－、Na＋濃度和血淋巴pH均顯著下降，血淋巴之二氧化碳分壓（pCO2）則顯著上升。蝦曝露於pH 5.6和4.4水中24 h，其血淋巴Cl－濃度佔滲透壓的百分比分別下降至36.5% 和35.2%；血淋巴Na＋濃度佔滲透壓的百分比則分別降至40.7% 和39.8%。蝦曝露於pH 4.4下24 h，血淋巴pH與HCO3－均顯著下降。 脫殼後期的淡水長臂大蝦曝露於pH 8.2環境下1天，Ca2＋淨攝取率為2.66 □mol/g/h，7天後，淨攝取率為0.08 □mol/g/h，甲殼Ca2＋濃度由剛脫殼時的2.99 mmol/g，7天後增加至5.34 mmol/g。蝦曝露於pH 5.6和4.4環境下1天，Ca2＋淨攝取率分別減少46.6% 和104.0%，其甲殼Ca2＋濃度分別減少19.8% 和35.9%。蝦曝露於pH 4.4下7天，Ca2＋淨攝取率減少530.2%，甲殼Ca2＋濃度則減少46.3%。 脫殼後期的淡水長臂大蝦曝露於pH 4.4環境下1天，流失Cl－和Na＋，與蝦曝露於pH 8.2比較，Cl－和Na＋淨攝取率分別減少155.8%和205.7%，曝露7天後，Cl－和Na＋淨攝取率分別減少55.4% 和598.4%。蝦曝露於pH 4.4下1天，其血淋巴之Cl－、Na＋和滲透壓分別減少3.1﹪、14.8% 和15.1%，曝露7天後，血淋巴之Cl－、Na＋和滲透壓則分別減少41.6%、32.3% 和31.7%。脫殼後期的蝦曝露於pH 4.4水中7天，K＋顯著流失，其肌肉中K＋濃度與蝦曝露於pH 8.2比較，也顯著地降低24.0%。 蝦曝露於pH 4.4環境下12 h，Na＋/H＋交換受阻與血淋巴pCO2上升，引起血淋巴酸化，血淋巴Cl－、Na＋和滲透壓均顯著下降。脫殼後期的淡水長臂大蝦曝露於pH 4.4環境下7天， Cl－、Na＋、K＋和Ca2＋顯著流失，導致血淋巴Cl－、Na＋和滲透壓下降、肌肉中K＋濃度顯著減少，甲殼中Ca2＋濃度也顯著地降低，並影響甲殼鈣化。蝦曝露於pH 6.8環境下，其攝餌率和脫殼次數顯著減少，導致成長減緩，不影響脫殼與攝餌而可接受的最低pH值為7.4。|
Giant freshwater prawn Macrobrachium rosenbergii were exposed to different pH levels and examined their tolerance. The median lethal concentrations（LC50）of pH at 24, 48, 72 and 96 h was then determined. In addition, the followings were also examined: growth rate, molting frequency and feeding rate; acid-base balance, osmolality and ion regulation of hemolymph; uptake of ions, calcification and ion concentrations in the hemolymph and muscle for postmolt M. rosenbergii. All prawns were killed when exposed to pH 3.6 in 24 h. The 24-, 48-, 72- and 96-h LC50 of pH on M. rosenbergii was 4.00, 4.05, 4.07 and 4.09, respectively. M. rosenbergii was more sensitive to acid environment as compared to crayfish Procambarus clarkii, Orconectes rusticus, O. virilis , Cambarus bartonii and tiger shrimp Penaeus monodon. The body weight and total length of prawns exposed to pH 5.6 were significantly lower than those of prawns exposed to pH 8.2 after 42 days. The 42- and 56-day EC50 of pH（pH level that reduced weight gain by 50% of that of the controls）were 5.61 and 6.25, respectively. Molting frequency and feeding rate of prawns exposed to pH 6.8 decreased significantly. The MATC of pH（minimum acceptable pH）based on molting and feeding was 7.4. Hemolymph pH, osmolality, Cl－ and Na＋ decreased significantly, whereas hemolymph pCO2 increased significantly for the prawns exposed to pH 4.4 after 12 h. The contribution of hemolymph Cl－ in the hemolymph osmolality decreased significantly to 36.5% and 35.2%, respectively, and the Na＋ to 40.7% and 39.8% for the prawns after 24 h exposure to pH 5.6 and 4.4, respectively. Hemolymph HCO3－ and pH decreased significantly after 24 h exposure to pH 4.4. Net influx of Ca2＋ was 2.66 and 0.08 □mol/g/h, respectively for the postmolt M. rosenbergii after 1 and 7 days exposure to pH 8.2. The carapace Ca2＋ concentration increased by 78.9%, and was 5.34 mmol/g for the postmolt M. rosenbergii after 7 days exposure to pH 8.2. Net influx of Ca2＋ decreased by 46.6% and 104.0% and carapace Ca2＋concentration decreased by 19.8% and 35.9%, respectively for the postmolt M. rosenbergii after 1 day exposure to pH 5.6 and 4.4. Net efflux of Cl－ and net efflux of Na＋ were observed for the postmolt M. rosenbergii after 1, 4 and 7 days exposure to pH 4.4. Hemolymph Cl－, Na＋ and osmolality decreased by 3.1%, 14.8% and 15.1%, respectively for the postmolt M. rosenbergii after 1 day exposure to pH 4.4, and by 41.6%, 32.3% and 31.7%, respectively after 7 days exposure to pH 4.4. Net efflux of K＋ was observed for the postmolt M. rosenbergii after 1, 4 and 7 days exposure to pH 4.4. The concentration of K＋ in the muscle decreased significantly by 24.0% for the postmolt M. rosenbergii after 7 days exposure to pH 4.4. In conclusion, the 24-, 48-, 72- and 96-h LC50 of pH on M. rosenbergii was 4.00, 4.05, 4.07 and 4.08, respectively. The MATC of pH（minimum acceptable pH）based on molting and feeding was 7.4. Hemolymph pH decreased by the inhibiting Na＋/H＋exchange and the elevation of pCO2 for the prawns exposed to pH 4.4 after 12 h. Hemolymph Cl－, Na＋and osmolality, muscle K＋ and carapace Ca2＋ decreased significantly due to losses of Cl－, Na＋, K＋and Ca2＋ for the postmolt M. rosenbergii after 7 days exposure to pH 4.4.