The histopathological effects of some pesticides on Oreochromis niloticus and determination of these effects with light and electron microscopes

Pesticides are widely used in many area but mainly in agricultural combat. However these compounds, which have significant advantages, they also have many harmful effects on the environment. Pesticides cause ecological problems by reaching natural environments from the places where they are used or produced. Therefore, we should know the possible effects of the pollutants which contaminate the natural environments on organisms living in those environments. Several methods are used to determine the effects of pesticides on organisms. In these methods, the toxicological tests applied in similar conditions give the best results. The results that gained from toxicological tests are analized and the adverse effects of pesticides on organisms are determined. So necesary measures against these adverse effects can be applied. The ultrastructural and histopathological investigation of organs has been widely used as a biomarker in Environmental Risk Assessment studies. The impact of environmental pollutants on the form-function relationship can be severe. Pollutants such as pesticides can easily disrupt the fragile thread which keeps this relationship intact. In this regard, ultrastructural reponses in the organs of living organisms are important and useful tools to determine the health condition and the effects of pollutants on the organisms. In the aquatic enviroments, fish is usually regarded as organisms of choice for assessing the effects of environmental pollution on aquatic ecosystems. Electron microscopic investigations can therefore effectively contribute to diagnosis of metabolic disturbances resulting either from low concentrations of contaminants which are not normally detected by standart chemical or analytical methods or from poor water quality conditions which ocur days or weeks after an uncertain event .Ultrastructural and cytopathological responses are sensetive enough to indicate early effects on the organisms to low concentrations of chemicals which makes them potentially useful biomarkers to assess environmental pollution. Cellular biomarkers including histopathological and ultrastructural effects represent an intermadiate level of biological organization between lower-level biochemical effects and higher-level individual and population effects. These types of responses typically ocur earlier than behavioral changes and are sensitive than growth or reproductive parameters and integrative parameters, provide a beter evaluation of organism health than a single biochemical response. The aim of this study is to determine possible alterations in organ (gills, liver, kidney) and gonad (testis) histology of Oreochromis niloticus individuals exposed to certain concentrations of Carbaryl, Diazinon, Lambda-cyhalothrin and Atrazine standarts with light and electron microscopes. At the first step of the study, the fish were exposed to certain concentrations of pestisdes mentioned before for 21 days and the histopatological alterations occuring in the tissues of organisms were determined by light microscope. Afterwards, ultrastructural and cytopathological changes were investigated by Scanning and Transmission Electron Microscopes (SEM and TEM). At the end of the study, it was observed that all pesticides which we evaluated their effects caused both histopathological and cytopathological changes in the tissues of O. niloticus individuals. Among the evaluated pesticides, Lambda-cyhalothrin showed the fastest and the most severe pathological effects. Also, it has been determined that the most of the pathological changes in the exposed organisms are the metabolic defensive reactions. Depending on the pesticide concentration, as the exposure time increased, the severity of the pathologies observed in living organisims increased in parallel. As a result of our studies, it was observed that cytopathologic changes occurred before histopathologic and ultrastructural pathologies. The fish organs which we have chosen for our work can be suggested as suitable biomarkers in determining the effect of a pollutant. In addition, during our study, it was observed that electron microscopes were very useful in determining early effects of pollutants. However, it is thought that more detailed studies, at molecular and gene expression levels, are needed to determine the earlier effects of pollutants.