Krasyuk Y. Toxicological resistance of Cyprinidae to the influence of the compounds of inorganic nitrogen

The thesis is dealt with the study of toxicological resistance of Cyprinus carpio L. and Ctenopharyngodon idella Val. (at different stages of their ontogenesis) to acute and long-term influence of ammonium and nitrite under both natural and experimental conditions. It has been found that the eggs of both species of fishes are rather resistant to the influence of NH4+ and NO2-. The survival rate of fish larvae decreases with increasing the duration of exposure. The stage of embryo hatching and changes in the type of larvae nutrition are the most critical periods of early ontogenesis. It has been shown that the resistance of Cyprinus carpio and Ctenopharyngodon idella to acute and long-term influence of ammonium and nitrite increases with increasing the period of adaptation and fish age. Joint action of the compounds of inorganic nitrogen and low temperatures on Cyprinus carpio and Ctenopharyngodon idella resulted in the decrease in the content of energetic substances in their liver (a decrease in liver index) and in the decrease in the intensity of detoxification, which is supported by the increase in the content of methemoglobin in their blood. This process was accompanied by a decrease a spleen index and in the decrease in the content of hemoglobin in their blood as a result of the significant inhibition of the processes of blood formation. The increase in the content of NH3 and NO2- (respectively by a factor of 2.5 and 4.0) in the tissues of the studied fishes was insignificant as compared to the increase in the concentration of ammonium and nitrite (respectively by a factor of 17.7 and 35.5) in the experimental water body. This fact is indicative of the capability of fish organism to resist toxic influence. It hes been found that Cyprinus carpio possesses a higher toxicological resistance to adverse effect of ammonium and nitrite as compared to Ctenopharyngodon idella at all the stages of their ontogenesis.