On The Characteristics Of The Salt Tolerance Of Cladocera Of Xiangjiang River System

Through the overall sample survey of the cladocera of Xiangjiang river system, combined with the acclimatization result, the representative category-Daphnia magna is regarded as the researching object of acclimatization, we take its two representative population-the big and small water daphnia magna (abbreviated as X. S^ X. B respectively). Under the condition of 30℃, we/use 14C to test the ingestion speed in 1 ‰-7 ‰ salinity and carry on an overall research to the salt tolerance of the two population. We get the following conclusion:①The ingestion speed of the Daphia magna change obviously with the change of salinity, little ford population has the highest ingestion speed at 3‰ salinity, big ford population has the highest ingestion speed at 2‰ salinity.② The Daphnia magna of the two population has obvious around-the clock ingestion rhythm, the morning and the evening are two peaks of ingestion. Salinity has no influence on the ingestion rhythm.③ The salt tolerance of Daphnia magna has obvious relativity with the environment of its former living waters, the salt tolerance of little for Daphnia magna is obviously higher than that of big ford daphnia magna is obviously higher than that of big ford daphnia magna.④ The salt tolerance of daphnia magna is closely related to the acclimatization method. When salinity surges down, the salinity for the two population to death is 1‰ and ll‰, when salinity change slowly, the salinity for the two population to death is 13. 5‰ and 14. 2‰.⑤ When salinity change slowly, the upper limit of the reproductionsalinity is 8.8‰ and 9. 4‰.⑥ The regression equation of the length and weight of the daphnia magna of Xiangjiang water system is as fellow.-X·S: lgW=2. 20421gL-0. 7347 (n=8 r=0.89 p<0.01) X· B: lgW=2. 13021gL-0. 70203 (n=12 r=0.98 p<0. 01)W-mg, L-mm。To sum up, the salt tolerance of the cladocera is common. The cladocera of Xiangjiang water system can perfectly acclimatized as the food of the young fishes and shrimps in the sea water under the salinity of 14‰, To some extend it can replace artemia parthenogentica which is becoming more and more deficient to enrich the bait system of fries in the sea and salty waters.