Histopathology of fishes' liver in the Saratov reservoir
In order to determine the level of anthropogenic load on the reservoir and form the ideas about the health of popu lations of aquatic organisms the ichthyopatological studies of mass fish species (Rutilus rutilus L., Abramis brama L., Perca fluviatilis L., Neogobius melanostomus Pallas, N. iljini Vasiljeva et Vasiljev, Proterorhinus marmoratus Pallas, Perc cottus glenii Dybowski) of the Saratov reservoir were carried out. Fish catching was carried out in the water area of the Koltsovo-Mordovin section of the reservoir in the period 2003-2013. As a bioindicator, the liver performing a variety of metabolic functions was chosen, which was studied by standard histological techniques. 8 types of histopathologi cal organ changes were revealed. They were divided into circulatory (hyperemia), inflammatory (infiltration of blood cells), proliferative (cystic tumors, pigmented tumors, fibrosis) and degenerative (vacuole and fat dystrophy, necrosis of hepatocytes). The most common type of disorders was hyperemia (the incidence of the disease varies from 31.4% to 88.2%). Discovered histopathologies have different severity for fish (2-4 points on a five-point rating system state). Damage, which is usually irreversible and life-threatening to fish, especially when exposed to stress factors and during the winter, prevailed. The main factor determining the pathological changes of the liver is the intoxication of fish with pollutants of organic and inorganic nature. Parasitological study of fish revealed in the liver of animal larvae of nema todes Eustrongylides excisus Jägerskiöld, Raphidascaris acus Bloch, Contracaecum microcephalum Rudolphi, which have a pronounced mechanical and toxic effect. Nematode invasion causes the most serious damage to this organ (infiltration of blood cells, necrosis of hepatocytes).