Accumulation Characteristics And Toxicity Response Of Corbicula Fluminea To Phenanthrene

In this study, phenanthrene was selected as poisonous substance, Corbicula fluminea was selected as experimental animals, using the principle and method of ecological toxicology, involvingmorphology, physiology, biochemistry and gas chromatography mass spectrometry (GC-MS) techniques, comprehensive study the effects of phenanthrene to the Corbicula fluminea. The main conclusions are as follows:1. Acute toxicity effects of phenanthrene on Corbicula flumineaThe actue toxicity tests of phenanthrene on Corbicula fluminea were determined with the semi-static test under labortory conditions for96-hours. With the equal logarithm interval method, five cocentrations of phenanthrene were set to estimate the actue mortality of phenathrene on Corbicula fluminea in96h. The results showed that24,48,72and96h LC50value were123、67.59、56.44and46.76mg/L, and it safe concentration (SC) of phenanthrene on Corbicula fluminea was4.676mg/L which is highly toxic substances according to the toxic chemicals on biological toxicity evaluation criteria. But compared with other species have been reported, Corbicula fluminea was a stronger resistance species for phenanthrene pollution, this suggested that there may be exist a pathway or material for phenanthrene degradation, and Corbicula fluminea has the high tolerance capacity for phenanthrene accumulation. But in any case, the results showed that the mortality of clam caused by phenanthrene exposed and exposure concentration had obviously time-effect and concentration-effect under the condition of the above safety exposure concentration. The fitting degree between the mortality of clam and phenanthrene exposure concentration (under24、48、72and96h) were0.8691、0.9263、0.9361and0.9747, and fitting degree between the mortality of clam (under70,56.64,45.83and30.08mg/L) and exposure time were0.9491,0.9503,0.9528and0.8065, respectively. That after the amount of phenanthrene in Corbicula fluminea body beyond its degradation metabolism ability or its body accumulation, then caused the damage, eventually led to the death of the individual level. And the cocentrations of phenanthrene in the environment tend not to exceed the safe concentration for Corbicula fluminea. So Corbicula fluminea can be used for resistant phenanthrene pollution, and it has the certain accumulation ability for phenanthrene, we can select the widespread benthos Asia freshwater Corbicula fluminea as one of the restoration of polluted water species.2. The effects of phenathrene on activity of antioxidant enzyme of Corbicula flumineaBased on the results of our acute toxicity experiment, we set5phenanthrene levels (50μg/L、25μg/L、500μg/L、1mg/L and2mg/L) which were below the safe concentration to explore the influence of fe on the antioxidant enzyme activities of the Corbicula fluminea. We explored the relationship between the activities of glutathione transferase (GST), glutathion peroxidase (GSH-Px), catalase (CAT) and superoxide dismutase (SOD) of different tissues and the phenanthrene concentrations at different time. The results indicated that there was some relationship between the phenanthrene concentration and the antioxidant enzyme activities. During the21days of exposuring in phenenthrene, the activities of CAT and GST had a fist increase and then decrease tendency, while there was no significant differences among SOD activities. We also found that there was a time-effect relationship between the exposured time and the antioxidant enzyme activities. And different enzymes had different sensitivities to phenanthrene. In the250μg/L group, we found that the CAT can be considered as main sensitivity biomarkers, SOD and GPx can be used as auxiliary sensitive biomarkers for phenanthrene pollution in Corbicula fluminea. 3. Effects of phenanthrene on the microstructural of hepatopancreas ans gills in Corbicula flumineaCorbicula fluminea were exposed to phenanthrene (0、250、1000μg/L) for21days. Observation the hepatopancreas and gill microstructure damage respectively in0,3,14and21days. The results showed that the structure of hepatopancreas and gill have damaged obviously after Corbicula fluminea were exposed to phenanthrene for14,21days compared with the control group for0day, hepatic tubule start cracks and fracture from the middle, the luminar area have increased significantly; the bubbling epithelium have gradually disappeared until the1000μg/L; the columnar epithelial cells have separated and disintegrated from basement membrance; nuclei have scattered distribution in hepatic tubule, and most of cell membrances have fused; due disintegration of basement membrance, and occurrence of cell debris between the tissue. At the same time, the gill of Corbicula fluminea also undergone significant structural damage after were exposed to phenanthrene, the frontal cilia become disorganized and gradually released from the top of gill flap; reduction of the water tubule area; the interlamellar junction have almost dissolved or breaked; the gill lamellae have already shrinked and collapsed. After exposure for21days, interlamellar junction and gill lamellae shape began to recover.4. The research on the accumulation of phenanthrene to Corbicula flumineaCorbicula fluminea were exposed to phenanthrene (250μg/L) for0、1、3、5、7、4days, accumulation of phenanthrene in hepatopancrea, muscle, gill and pallium were measured using GC-MS, the correlation between accumulation and antioxidant enzymes (SOD、CAT、GST and GPx) were also analized under labortory conditions. The results found that different tissue have different cumulative time to reach the highest accumulationof phenanthrene, specifically first hepatopancreas, gills and mantle, followed by muscle tissue; addition, the accumulation of phenanthrene was increasing with the extension of time, it will decreasinged with with extension of time when it reached a certain accumulation of phenanthrene.The results suggesting that Corbicula fluminea have certain metabolic capacity to low concentrations of phenanthrene. The correlation between accumulation in hepatopancrea and GST activity had significant differences (P<0.05), the correlation coefficient was0.6961; and the correlation between accumulation in gill and GST activity had highly significant differences (P<0.01), the correlation coefficient was0.9076; but the correlation between accumulation in muscle, pallium and antioxidant enzymes activity had no significant differences (P>0.05). This suggests that GST activity can be used as the sensitivity indicators of phenanthrene pollution in hepatopancreas and the gills in Corbicula fluminea.