Toxic Effect of Phoxim on Giant River Prawn Macrobrachium rosenbergii
To evaluate the potential threat of phoxim to aquatic animals,giant river prawn(Macrobrachium rosenbergii)with average body weight of(1.2±0.2)g was placed in 30 L of water with phoxim concentrations of 0 μg/L(control group),3.125 μg/L,6.25 μg/L,12.5 μg/L,25.0 μg/L,50.0 μg/L and 100.0 μg/L for acute toxicity test at water temperature of(21.0±0.5)℃by semi-hydrostatic method.In order to further explore the toxicity and reversibility of phoxim to giant river prawn,the prawns were exposed to 1/3 96 h median lethal concentration(LC50)of phoxim for 4 d,then moved to clean water for 7 d.Prawns reared in clean water were kept as the control group.1/2 water was exchanged every day,and 3 parallels were included in each group.At the 0th,4th and 11th days,the hepatopancreas,gills and intestines were randomly sampled and fixed with Bouin's solution for histopathological observation;at the 0th,1st,2nd,4th,and 11th days,the hepatopancreas and muscle tissues were randomly collected,flash frozen in liquid nitrogen,and stored at-80℃for detection of the oxidative stress enzyme activity and immune gene expression through multiple biomarkers.It was found that the LC50 of phoxim was 16.834 μg/L for 24 h,10.644 μg/L for 48 h,8.570 μg/L for 72 h,and 6.988 μg/L for 96 h.The 4-day exposure to phoxim resulted in severe damage to the hepatopancreas,gills and intestinal tissues of giant river prawn including disappearance of the star-shaped lumen and the vacuole structure of the tubules in the hepatopancreas,swollen top of gill filaments at the base of gill,injured intestinal villi,and epithelial cells abscission in intestinal tissue.The activities of alanine aminotransferase(GPT)and aspartate aminotransferase(GOT)were significantly decreased(P<0.01),indicating serious damage of hepatopancreas function.Hydrogen peroxide(H2O2)and malondialdehyde(MDA)were shown to be accumulated in the hepatopancreas(P<0.01),while the activities of superoxide dismutase(SOD)and glutathione peroxidase(GSH-pX)were significantly decreased(P<0.01),which represented the oxidative stress caused by phoxim.The significant decrease in the activity of acetylcholine(AChE)(P<0.01)and down-regulated expression level of four immune-related genes(alf,hsp,hemocyanin and proPO)demonstrated the disruption in nervous and immune systems(P<0.01).Histopathological damage,hepatopancreatic function,oxidative stress,and disruption in nervous and immune system were partly recovered after 7-day decontamination in freshwater,without recovery to the initial level,indicating that part of the damage of phoxim to giant river prawn was irreversible.
NETL
NSTL
万方数据
