The Toxic Effects Of Sodium Selenite Anhydrous On Loach (Misgurnus Anguillicadatus)

Loach (Misgurnus anguillicadatus), a species of freshwater fish, is distributed in China far and wide. It has high capacities of life-force and anti-pollution, and comprehensive values in edible and medicinal. It has been become an economic cultivated fish gradually. Selenium is one of the necessary microelement for all kinds of animals. However, evidences demonstrate that superfluous selenium can bring toxic effects to some of animals. Up to now, very few studies can be found of the toxic effects of selenium on loach.Therefore, the purposes of this study are 1) To identify the toxic mechanisms of sodium selenite anhydrous. 2) To add a method and biomarker to detect and prevent environment pollution. 3) To offer scientific evidence to protect fish and pathologic reference to fish's cultivation.In this study, the acute and sub-acute toxic effects of Na₂SeO₃ on loach were conducted. The durations of experiment are both 96 hours. The details of methodology are as followings:1) Acute toxic effect: total of 56 loaches were selected as the subject for the acute toxicity of experiment. They were divided in 7 groups randomly. Normally, selenium can be found in Na₂SeO₃. In the present study, the solutions with varied concentrations of Na₂SeO₃ were used as the intervention factors which were 5, 10, 20, 40, 80, 160mg/L respectively. Each group meets the specified concentrations of Na₂SeO₃ and the last group was as the control group. The loaches were cultivated in the different containers which were poured with varied concentrations of Na₂SeO₃ and pure water. The number of the dead fish was registered per 24h and the lethal concentration at 50% (LC50) was calculated and analyzed.2) Sub-acute toxic effect: another 50 loaches were selected for the inferior lethal toxicity of experiment. They were divided in 5 groups randomly. The solutions with varied concentrations of Na₂SeO₃ were used as the intervention factors which were 0, 10, 20, 30, 40mg/L, respectively. Two fish were killed after 24h, 48h, 72h, 96h in each of the container respectively. The blood and the liver of killing fish were collected and analyzed.The results showed that 1) The LC50 at 96h of Na₂SeO₃ to loach is 44.8mg/L. The result demonstrated that the Na₂SeO₃ has strong lethal effect on loach. There is a positive relationship between the concentration of chemicals and their toxic effect on loach. 2) The effect of Na₂SeO₃ to the activities of Superoxide dismutase(SOD) , Glutathione S-transferases (GST) in blood of loach showed tendency of inhibition- induction- inhibition effects. However, the effect of lower concentrations solutions of Na₂SeO₃ to the activities of acetylcholinesterase(AChE)showed a tendency of induction- inhibition effects, while high level concentration solution of Na₂SeO₃ to the activities of AChE showed inhibitory effects. 3) For the damage of Na₂SeO₃ to erythrocyte, the Na₂SeO₃ can lead to the existence of the abnormality of the nuclear and micronucleus. Nuclear protruding is the main symptom. Generally speaking, the rate of the abnormality of the nuclear is increased with the increasing of Na₂SeO₃ concentrations and the lengthening experiment time. 4) The damage of Na₂SeO₃ to the liver tissues of loach exhibits the liver cells expanding, the liver cells arrangement altering. The liver structure is changed which may caused by inflammation during the immerging in the high level Na₂SeO₃ at 96h.Base on the results obtained from this study, it is concluded that 1) Na₂SeO₃ has strong lethal effect on loach. 2) The sub-lethal concentrations of Na₂SeO₃ may have the effects on the activities of SOD, GST and AChE. 3) The sub-lethal concentrations of Na₂SeO₃ may lead to the abnormality of the erythrocyte nuclear and may cause the appearing of inflammation, in return, may influence the arrangement of structure of liver cells.