Study On Eco-toxic Effects Of Dicofol On Loach (Misgurnus Anguillicaudatus)

With the increasing of emphasis on food security and international trade in food, maximum residual limits of pesticides in aquatic products have been enforced in many countries. More attention was paid to improve and enhance the quality of fishery environment. As an alternative pesticide of DDT, dicofol (DCF) has been concerned by a lot of scholars since its initial production. DCF has low toxic to rodents, and can efficiently control acarid, and useful in promoting the harvest of agricultural crops. However, more and more reports suggested that DCF can exist in environment for a long time, it is hypertoxic to aquatic organisms and harmful to animals.The research on biochemical indexes which indicate the potential harm of pollutants was high lighted. Vitellogenin (Vtg), Glutathione S-transferase (GST) and Acetylcholinesterase (AChE) etc. are useful bio-indicators for predicting eco-toxicity of pollutants. Information on DCF concentrations in various environmental media was very limited. The bio-chemical effects of DCF on aqutic organisms were seldom reported in China compared with that in western countries.Loach (Misgurnus anguillicaudatus) is widely distributed in fresh water and sediment in China. It played an important role in the monitoring of water environment. Loach's meat is delicate, eutrophy and delicious. Potential safety hazard of DCF in fishery environment and aquatic product have been doubted and worried by more and more people. Therefore, loach is selected as an experimental organism for preliminary study of the bio-chemical effects of DCF in sediment on fish. This experiment aimed to elucidate the moving and transformation of DCF in fishery environment, and to provide useful information for evaluating and forecasting the potential harm of DCF.This study was carried out in laboratory, loach samples were exposed to 0, 5, 10, 20 and 40 mg·kg^-1 DCF,respectively, exposure time in each dosage last for 24 h, 48 h and 96 h respectively. Activities of GST and AChE, and Vtg concentration in the blood serum were examined, at the end of the experiment, DCF residue in the muscle, skin, liver, intestine and gill were determined. In addition, an analysis method for DCF residue in sediments by gas chromatography was developed.The results were as following:(1) The GST activities and Vtg concentrations in the blood serum of experimental loach were higher and AChE activities were lower than that of control, respectively. The GST activities were significantly increased with increasing DCF concentration (r=0.998⁰.999, p<0.01). On the other hand, the AChE activities were significantly decreased (r= - 0.906 - 0.946, p<0.10). A positive correlation between Vtg concentration and DCF level was observed. The correlation coefficient with significant level were 0.825 with p<0.10, 0.719 with p>0.10, 0.885 with p<0.10 for 24 h, 48 h and 96 h, respectively. These results indicated that the GST activity and estrogenic level of male loach could be increased by, but the AChE activity in blood serum could be decreased by DCF.(2) Generally, DCF residuals in the loach tissues increased with exposure time and DCF dosage. There was significantly positive correlation between DCF residuals in liver and DCF dosage (r= 0.976⁰.994, p<0.01); Also, a positive correlation between DCF residuals in skin or intestine and DCF dosage was observed (r=0.888⁰.985, p<0.05 and p<0.01, respectively). There was positive correlation between DCF residual in gills or muscle and DCF dosage was existed after 24 h or 48 h exposure (r = 0.953 ⁰.993, p<0.05 or p< 0.01), but indistinctively positive for 96 h exposure (r= 0.566⁰.831, p> 0.05 or p>0.10).(3) The absorption capacity for DCF was in the following order: intestine>liver>skin>gill>muscle after 24 h exposure, and intestine>skin>liver>gill> muscle after 48 h exposure, and intestine>skin>gill>liver≈muscle under the concentration of 5 mg·kg^-1 DCF, gill > intestine > skin > muscle > liver under the concentration of 10 mg·kg^-1 DCF, intestine>skin> gill > liver >muscle under the concentration of 20 mg·kg^-1 DCF, and intestine> gill > skin > liver >muscle after 96 h exposure or under the concentration of 40 mg·kg^-1 DCF. DCF levels were highest in intestine and lowest in muscle. The DCF levels in gill, skin and liver were affected by DCF concentration or exposure time.(4) After exposure to DCF, the DCF residuals in eatable tissues (skin and muscle) were higher than the limits for meat product prescribed in European Union, Japan, Canada and CAC (Codex Alimentarius Commission) which was 0.05 mg·kg^-13 mg·kg^-1, and higher than the limit in Japan, which is 0.01 mg·kg^-1 .(5) The detection limit of DCF in sediment sample is 3μg·kg^-1.The recovery of this analysis method range from 80.8% to 99.5%, and the relative standard deviation (S.D.) of the two parallel samples is 5.4%⁷.2%, when 3⁵0μg·kg^-1 DCF was supplemented. The result suggested that this method is available to detect trace DCF in sediment sample, due to its relative high sensitivity, accuracy, repeatability and maneuverability.