Life History And The Toxicity Sensitivity Of Corophium Acherusicum (Crustacea: Amphipoda)

Amphipods are ecologically important members of benthic infaunal communities and are one of the most sensitive members among benthic communities to anthropogenic disturbance, especially to pollution. They are tolerant to varying sediment physicochemical characteristics and are ideal testing organisms for sediment toxicity test. Corophium acherusicum in this study is a corophiid amphipod species, builds a U-shaped tube in sediments ranging from coarse sand to silty clay in the intertidal zone. The multi-generation cultivation system of C. acherusicum has established under the constant temperature in the laboratory. The life history and the toxicity sensitivity C. acherusicum were studied in this paper. The main results are listed as follows:1. C.acherusicum was cultured in laboratory at 20℃. The life-cycle and reproduction-cycle tests of the first and second generation C.acherusicum were carried out in order to determine survival, sex ratio, number of juveniles per female, the total number of offspring, reproduction frequency. The results showed that the longest survival time of the first generation female was 190d, the second generation was 170d; the longest survival time of the first generation male was 100d, the second generation 120d; the longest survival time of male was only about half of the female; the life cycle of the first and second generation were respectively 64d,58d; the sex ratio of the first and second generation juveniles were respectively 1:0.76,1:0.75 (females:males); number of juveniles per female were respectively 13-28 juveniles/female,11-27 juveniles/female; C.acherusicum reproduction at least 5 times; the first and second generation C.acherusicum produced offspring 64-149 juveniles/female,81-127 juveniles/female respectively.2. The cadmium-spiking water-only toxicity tests were carried out in order to determine the toxic sensitivity change rule of different generations and each phase in its whole life of C. acherusicum. The toxic sensitivity of C. acherusicum from f1,f2,f3,f4 generation were:f1 generation juveniles were less sensitive than f2 generation;f2 generation juveniles were near sensitive than f3 generation and more sensitive than f4 generation. f2 generation and f3 generation are amenable to the toxicity test. The results showed that the toxic sensitivity of C.acherusicum gradually weakened from one-week juveniles,two-week juveniles to three-week juveniles. Four-week juveniles were more sensitive than three-week juveniles, less than one-week and two-week juveniles. Considering life history research results, this study suggests that two-week juveniles are amenable to the toxicity test. Toxicity sensitivity of lab cultured C.acherusicum was comparable to those of field collected C.acherusicum in toxicity test.3. The 10-d sediment toxicity test has been developed with cadmium-spiked sediment using two-week juveniles of lab cultured f1, f2, f3, f4 generation and field collected of C.acherusicum. The LC50 values of f1, f2, f3, f4 generation C.acherusicum were 291.673,261.857,215.792,306.459 mg·kg-1 respectively. The LC50 values of field collected of C.acherusicum was 514.927 mg·kg-1.The toxic sensitivity change rule of different generations in spiked sediment test was coincident with the rule of C.acherusicum in spiked water test. C.acherusicum cultured in lab was more sensitive than that of collected in field.4. The effects of cadmium on the growth, antioxidant defense system and lipid peroxidation in C.acherusicum were investigated with cadmium-spiked poor water toxicity test. Dry weight and survival of C.acherusicum decreased in accordance with the increase of metal ions concentrations. The contents of cadmium in C.acherusicum were elevated with the increasing concentration of cadmium and the prolonged time. The SOD activities were decreased with the prolonged time. The SOD activities were increased at a low concentration of cadmium, the activity was decreased at intermediate concentration of cadmium, while the activity was increased at high concentration. The MDA activity showed a parabola trend with the increasing concentration of cadmium and the prolonged time. The MT content were increased at preliminary of exposure test, the content was decreased at intermediate of exposure test, while the content was increased at late of exposure test. The dry weigh and MT activity are more suitable to be the end point for toxicity test.Results from a variety of experiments in this study indicate that C.acherusicum has a relatively short life-cycle and is easy to be cultured in laboratory. In addition, C.acherusicum cultured in lab is sensitive to the toxicity of sediment as well as that of field collected. In conclusion, C.acherusicum is an ideal testing organism for sediment toxicity test. The results of this study indicate that more and more C.acherusicum will be cultured in lab and used in the sediment toxicity test later.