Research On Energy Characteristics Of Progressive Failure Process Of Deep Marble Under Loading And Unloading

During the flood season,fast-flowing currents release from high dams and inject air into the stilling basin.When the gas pressure downstream of the dams exceeds atmospheric pressure,total dissolved gas(TDG)supersaturation occurs.High levels of TDG will last for a long time,due to the slow release of dissolved gas in natural rivers.It causes gas bubble disease(GBD)and mortality in various fish species,which has become one of the major risks threatening the ecological environment of rivers.However,existing studies which investigate the effects of TDG supersaturation on fish have mainly focused on fish tolerance,avoidance,and swimming ability,and few have explored the mechanisms of intrinsic effects of TDG supersaturation on fish.Therefore,further studies on the intrinsic mechanisms of TDG supersaturation in fish are particularly important.In this study,grass carp(Ctenopharyngodon idellus),one of the "the four famous domestic fishes" in China,was taken as the research object.Different TDG levels and exposure times were set in the laboratory.Representative stress-related genes such as Heat Shock Proteins-60(HSP60),Heat Shock Proteins-70(HSP70),Heat Shock Proteins-90(HSP90),and immune-related genes such as Major Histocompatibility Complex I(MHC I),Major Histocompatibility Complex II(MHC II),Interleukin-1(IL-1),Interleukin-6(IL-6),Tumor Necrosis Factor(TNF)were selected as evaluation indicators.The effect of TDG supersaturation on the immune and stress response of the grass carp were investigated by gene expression analysis.The main conclusions are as follows:(1)Experimental fish exhibited different GBD symptoms at relatively high TDG levels(130%,135% and 140%),such as exophthalmos,abdominal swelling,and gill bleeding.A small number of grass carp died in the tanks with high levels of TDG supersaturated water late in the experiment.(2)Compared with the control group,the relative expression of HSP60,HSP70,HSP90,MHC I and MHC II in the liver of grass carp showed an increasing trend at 125%,130%,135% and 140%.However,there was no significant change in TNF.During the experiment,both the stress-and immune-related genes were highly expressed in the liver.These results showed that TDG supersaturation,which is treated as an environmental stressor,can enhance stress response and immune function in the experimental fish.(3)After exposed to TDG supersaturated water,the expression of stress-and immune-related genes in the liver of grass carp is strongly correlated with the exposure time.At 120% TDG,the expression of HSP60,HSP70,HSP90,MHC I,IL-1 and IL-6gene were time specific.(4)The stress-and immune-related genes in the liver of grass carp exhibit different expression patterns in the TDG supersaturated water.HSP90,MHC II,and IL-1 genes,which may be involved in the stress response and immune regulation during the early stage of TDG supersaturation stress,highly expressed at 6 and 12 h.MHC I and IL-6genes highly expressed at 48 h,and it indicates that these genes may play a protective role in the later stage of TDG supersaturation stress.There is no significant change in the expression of TNF,suggesting its low sensitivity to TDG supersaturation.