博士 / 國立臺灣海洋大學 / 水產養殖學系 / 92 / 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 mmol/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.
| Identifer | oai:union.ndltd.org:TW/092NTOU5086003 |
| Date | January 2004 |
| Creators | Su-Mei Chen, 陳淑美 |
| Contributors | Jiann-Chu Chen, 陳建初 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 130 |
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