Study On Detoxification And Mechanism In Main Organs In The Freshwater Crab Sinopotamon Henanense After Cadmium

Cadmium（Cd）is a toxic and non-essential heavy metal element,which not only endangers the growth and development of animals and plants,but also threatens human health and life through propagation by food chain.Frequent Cd in industrial manufacturing causes serious environmental pollution,especially in water,which has become a worldwide problem.The benthic crustaceans are useful indicators used in monitoring of fishery environment and management of water quality.Based on the above purposes,the gills and hepatopancreas of the freshwater crab Sinopotamon henanense were investigated to illustrate the detoxification and specific mechanism of Cd under nature from different perspectives.Crabs were exposed to 0,50,100 and 500μg·L^-1 Cd Cl₂for 14 d followed by 21 d of depuration.The microstructure of the gills and hepatopancreas were observed by histopathological and histochemical techniques,as well as biomacromolecules（polysaccharides,neutral lipids,DNA and total proteins）of the hepatopancreas.The Cd content in organs and water were tested by flame atomic absorption spectrometer,and the oxidative stress and neurotransmission biomarker（SOD,CAT,GR,Trx R,MDA and ACh E）of the gills and hepatopancreas were detected by microplate reader.Besides,the IBR and PCA showed the suitable biomarkers delineating the health of S.henanense in a Cd-contaminated environment.This thesis aimed to provide new insight for optimizing the indicators of crustaceans and scientific bases for the aquaculture and the monitoring of heavy metal pollution in freshwater ecosystem.The results are as follows:The first,the histopathological lesions of the gills and hepatopancreas of S.henanense were severe,including the necrosis,hyperplasia and vacuolation of epithelial cells after 14 d of Cd exposure.The histopathological indices(I_his)revealed more serious injuries of the hepatopancreas in 100 and 500μg·L^-1 Cd Cl₂ groups.Additionally,the content of polysaccharides and neutral lipids descended,and the DNA synthesis enhanced in hepatopancreas among all group.The structure of the gills and hepatopancreas returned to normal,and the I_his manifested better recovery of the gills after 21 d of depuration.The accumulated polysaccharides and neutral lipids were found in hepatocytes,as well as controlled DNA.The recovery of DNA was the best among the biomacromolecules by histochemical evaluation.The second,the Cd concentration of the gills and hepatopancreas rose in a concentration-dependent manner after exposure.The bioconcentration factor（BCF）showed that the Cd ccontent of the gills was 2.47±0.75 times higher than that of the hepatopancreas.Cd residues in 50 and 100μg·L^-1 Cd Cl₂ groups decscended to normal after 21 d of depuration.The elimination coefficient（EC）indicated that more than58.80±8.53%Cd was discharged from the gills,and the Cd content from the gills was 1.28±1.80 times higher than that from the hepatopancreas.The third,the activation in GR of the gills,and SOD,CAT,GR and Trx R of the hepatopancreas were highly significant（p<0.05）,with extremely decreased ACh E and increased MDA after Cd exposure.All biomarkers of gills,ACh E and MDA of the hepatopancreas recovered,but the antioxidant systems of the hepatopancreas were activated continuously during the depuration.Spearman’s and Pearson’s coefficients exhibited that there were strong correlations（p<0.05）between Cd content and activities of SOD and CAT of the hepatopancreas during exposure and clearance,and antioxidant enzymes were negatively correlated with ACh E in two organs.The I_his,GR and MDA were screened by IBR and PCA,which sensitively responsed to Cd stress.In conclusion,S.henanense can resist Cd stress through antioxidant defense,and recovered in Cd-free environment.Hepatopancreas took on the detoxification,and gills showed high recovery and clearance ability.The I_his,GR and MDA are the suitable biomarkers indicating detoxification ability,which promotes the application and development of crab in water environment monitoring.