Study On The Toxicity Effects Of Two Kinds Of Organophosphorus Pesticide Dimethoate And Chlorpyrifos On Urostyla Sp.

In recent years, with the development of agriculture, pesticide application is more and more widely, the application of pesticides in agriculture has brought huge economic benefits, but also caused great harm to the agricultural ecological environment simultaneously. The pesticide pollution to the ecological environment, biological survival and human health brought irreversible adverse effects. Therefore, pesticide toxicity is becoming a hot topic in the research field of toxicology.Protozoa is a group of single-celled animals, some species of which can be used as biological indicator.Drugs dimethoate and chlorpyrifos were used as toxicantwhile ciliated protozoa Urostyla sp. as subject.The concrete research contents were as follows:Determination of two kinds of organophosphorus pesticide dimethoate and chlorpyrifos the median lethal concentration of Urostyla sp. for 24 hours.Based on this median lethal concentration, minimum effective concentrations of that two kinds of organophosphorus pesticide of the impact on the asexual binary fission rate(times/day) of Urostyla sp. were determined.. Using the transmission electron microscope, comparative observations of the ultrastructures of Urostyla sp. with two pesticide culture mediums were performed. This work aimed to reveal any change of submicroscopic structure of cell of Urostyla sp. in early stage of rate-changing in asexual binary fission poisined by two kinds of pesticide.The method of determined cell fission rate(times/day): put the monoclonal culture of cell into a glass pit with quantitative food source( one cell each pit). Method for measurement of cell fission speed(times/day) was list in the following: put cells from monoclonal cultivation into pits on a glassand add food source(one pit each),then counted the cell number in the second day to determine the division times of cultured cells in a day, then leave one cell(in the best growing-condition) continually growing with rest ones abandoned. Daily repeat the above work and finally determine the daily division times of cultured cells in a glass pit.. Every 168 hours for a cycle. Preparation of gradient concentration of dimethoate, chlorpyrifos culture, for culturing Urostyla sp.Determination of daily fisssion times under every concentration. The experiment was divided into the experimental group and control group,30 pits for a large sample.Then using SPSS software find out the daily binary fission times(normal cell) of experimental group and the control group in order to show the significant differences on the range of minimum effective concentration of dimethoate and chlorpyrifos.Using transmission electron microscopy technology, inside-structures of cells in both of the experimental group and the control group were observed with the main observing apparatus: mitochondria, cell nucleus and cytoplasm. The results were as follows:1.Median lethal concentration: the LC50 of Dimethoate on Urostyla sp. for 24 hours was 0.625mg/Lwhile chlorpyrifos was 0.029mg/L.Under the effect of acute toxicity, the tolerance of Urostyla sp. on dimethoate is higher than that of chlorpyrifos.2. The minimum effective concentration range of dimethoate impact on Urostyla sp.asexual binary fission rate was 0.264~0.275mg/L; the minimum effective concentration range of chlorpyrifos impact on Urostyla sp. asexual binary fission rate was 0.0075~0.0093mg/L. Chronic toxicity of dimethoate and chlorpyrifos to Urostyla sp. within 168 hours showed the inhibition of cell fission rate.The concentration obtained from this experiments is the minimum effective concentration, far below the national emission standards for sewage----the organophosphorus pesticides emission limit was 0.5mg/L.3. The ultrastructural observation of transmission electron microscopy, the cell asexual binary fission rate was effected by the minimum effective concentration of two kinds of pesticides, the cell showed: the micronucleus inside the cell showed nuclear membrane deformated and incomplete,chromatin condensated; macronucleus membrane ruptured, chromatin condensated,the number of nucleolus reduced; it was showed in the mitochondrionthat the double membrane structure indistinct, internal cristae structure was not clear.The result revealed the subtle physiological reaction of Urostyla sp. effected by toxin.The concentration affecting the speed of asexual binary fission Urostyla sp. was lower than the median lethal concentration, and far lower than that of the national standard. to the present work provided scientific and objective data on intelligent use and safety evaluation of this two kinds of organophosphorus pesticide, which was a supplement and contribution for original index system.