| Mangrove clam(Polymesoda erosa)is one of the main bivalves in mangrove area which has high nutritional value of its soft part,it is not only rich in amino acids and vitamins,but also contain low fat,both are necessary for human body.However,with the pollution of the environment and the excessive utilization of its wild resources in recent years,the number of P.erosa has been decreased dramatically.In order to investigate the effects of heavy metal chromium(Cr)on the growth and survival of P.erosa,based on the obve results and our experimental date,we measured the ingestion rate,antioxidant enzyme activity of gill tissue,gill tissue structure and micronucleus frequency of blood cells of P.erosa under the stress of hexavalent chromium(VI)were determined.The main contents and results are as follows:(1)The ingestion rate of P.erosa under the stress of Cr(VI)was determined by filtration method.The concentration gradient of Cr(VI)was set to be 0,30,60,120,180,and 360 mg/L.Samples were respectively taken at 0 h,4 h,8 h,12 h,24 h and 48 h.The results showed that the feeding rate and the concentration of Cr(VI)decreased with the prolongation of experimental time.The results showed that the ingestion rate of P.erosa decreased with the increase of dry weight of the software without the influence of Cr(VI).Under the condition of Cr(VI)stress,the ingestion rate of P.erosa decreased with the prolongation of experimental time,and the feeding rate decreased with the prolongation of experimental time under the same concentration of Cr(VI)stress,and decreased with the increase of Cr(VI)stress concentration at the same time.(2)The activity of CAT and SOD in gill tissue of P.erosa under Cr(VI)stress was determined.The concentration gradients of Cr(VI)were also set to be 0,30,60,120,180,and 360 mg/L.Samples were taken at 0h,4h,8h,12 h,24h and 48 h,respectively.The results showed that the activities of SOD and CAT in gill tissue of P.erosa changed comparatively.With the progress of the experiment,both SOD and CAT showed the first change.The higher the concentration of Cr(VI),the more obvious the decrease of SOD and CAT activities,and the faster the response of SOD to heavy metals is than that of CAT.(3)The gill tissues of P.erosa under Cr(VI)stress were observed by making histological sections.The concentration gradient of Cr(VI)was set to be 0,30,60,180,and 360 mg/L.Samples were taken at 48 h.The samples of gill tissue were prepared into histological sections and observed under optical microscope.The results showed that Cr(VI)had obvious toxic effects on gill tissue of P.erosa.With the increase of Cr(VI)treatment time,gill filaments proliferated seriously,and twisted,the ends of gill filaments expanded severely,and epithelial cells proliferated and necrosed.(4)Make blood smears of P.erosa under the stress of Cr(VI).Measure the micronucleus frequency of blood cells.Use potassium dichromate to carry out the stress experiment of Cr(VI).According to the results of the preliminary experiment,set the concentration gradient of Cr(VI)to 0,30,60,180,and 360 mg/L.Sample once every day for 4 days.Make blood smears with optical display.The results showed that under the stimulation of Cr(VI),the micronucleus production frequency of P.erosa blood cells was in obvious dose and time effects,and the highest micronucleus frequency was 11.6‰.This study preliminarily analyzed the toxicity mechanism of Cr(VI)stress on P.erosa,enriched the changes of physiological and biochemical indexes of P.erosa under heavy metal stress,and had great significance for protecting and exploiting wild P.erosa resources,developing artificial breeding and disease control of P.erosa. |
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