Studies On The Toxicity Of Subchronic Copper Exposure To Main Tissues Of Freshwater Mussel Anodonta Woodiana

To explore the toxic effects and mechanisms of subchronic Cu²⁺exposure on gill,digestive gland and kidney tissues of mussel Anodonta woodiana,three Cu²⁺ concentration groups?0.137,0.548,2.192 mg L-1?and a control group were set up for 28 d according to the LC50?109.55 mg L-1?of Cu²⁺ exposure for 96 hours.The Cu²⁺ accumulation,the activities of superoxide dismutase?SOD?,catalase?CAT?,glutathione peroxidase?GPx?,and glutathione S-transferase?GST?,and the contents of reduced glutathione?GSH?and malondialdehyde?MDA?,and total antioxidant capacity?T-AOC?were tested in the gill,digestive gland and kidney tissues of A.woodiana.Meanwhile,the morphological changes of cells in the gill,digestive gland and kidney tissues were observed.The experimental results showed that:The first,the gills,digestive glands and kidney tissues of A.woodiana all showed significant enrichment effects on Cu²⁺.Cu²⁺ accumulation in all tissues increased with the increase of Cu²⁺ concentration and exposure time.The second,cilia abscission,haemocyte infiltration and nuclear pyknosis in gill tissue were observed after Cu²⁺ exposure.Cu²⁺ induced epithelial cell exfoliation,cell disruption and haemocyte infiltration in the digestive gland tissue and caused scattered or even fragmented distribution of glandular epithelial cells,vacuolation of glandular epithelial parenchymal cells and haemocyte infiltration in kidney tissue.The third,in gill tissue,the activity of antioxidant enzymes SOD,GPx,and GST were significantly induced?p < 0.05?,while the activity of CAT was significantly inhibited?p < 0.05?after Cu²⁺ exposure in comparison to the control group.In addition,the content of the antioxidant GSH decreased significantly?p < 0.05?.T-AOC in gills was significantly higher?p < 0.05?than the control group after exposure to Cu²⁺ for 14,21 and 28 d.MDA content in gills increased with increased Cu²⁺ concentration and extended exposure time,showing “dose-effect” and “time-effect” relationships.The fourth,at the same time,with the increase of Cu²⁺ concentration,the activities of SOD and CAT in digestive gland basically increased first and then decreased,GPx and GST basically showed a downward trend and GSH content roughly showed an upward trend.Cu²⁺ exposure caused significant increase in the contents of T-AOC and MDA in digestive gland?p < 0.05?.The contents of T-AOC and MDA in digestive gland increased first and then decreased with the prolongation of exposure time at the same concentration and different time.The fifth,SOD activity was significantly induced?p < 0.05?while the changes of CAT,GPx,GST activities and GSH content were not obvious under Cu²⁺ exposure in kidney tissue.The contents of T-AOC and MDA in kidney were significantly increased in moderate and high concentrations of Cu²⁺ exposure?p < 0.05?compared with the control group.The contents of T-AOC and MDA in kidney increased first and then decreased with the prolongation of exposure time at the same concentration and at different time.From the above results,the following conclusions could be drawn:Firstly,With the increase of copper concentration and the prolongation of exposure time,the damage of gill,digestive gland and kidney tissue cells of A.woodiana was aggravated.Secondly,Although the antioxidant system of gill,digestive gland and kidney tissues of A.woodiana was activated under copper exposure,the above three tissues was still damaged by oxidative stress to varying degrees.Thirdly,GPx,GST and GSH in gill tissue were sensitive to copper.However,CAT in digestive gland tissue was sensitive to copper and SOD in kidney tissue was sensitive to copper.Different antioxidant indices in the above tissues can be used as biomarkers for monitoring and evaluating copper pollution in water.