Spermatogenesis disorders in sterlet (Acipenser ruthenus Linnaeus, 1758) in water area of the Kakhovka Reservoir

Purpose. To conduct histological studies of sterlet spermatogenesis in technogenic conditions. To determine the level of reproductive system disorders, to identify possible causes of abnormalities. To determine the prospects for using histological monitoring data in morphophysiological studies and ichthyological practice. Methodology. The primary materials were obtained in the conditions of “Oasis Bisan” LLC (Mykolaiv) and the Dnipro River mouth. The lab processing of histological samples was performed in accordance with generally accepted methods and manuals. Histological studies were conducted using original equipment and techniques specifically adapted for fish tissues. The results obtained were processed by methods of variational statistics using Microsoft Excel. Findings. Under conditions of prolonged technogenic load on water areas, changes occur in fish gonads, which can be considered bioindication zones. The reaction of gonadal cysts was manifested in the separation of the epithelium from the basement membrane. The spermatogonia count in the basal cell layer was significantly lower than normal. Asynchronous and wave-like changes in the initial stages of spermatogenesis indicate a shift in the time of the cell cycle, which provokes a failure of morphogenetic processes. With testicular atrophy, a significant decrease in the linear parameters of interstitial cells was observed – by 6.58, 3.05 and 3.53 µm (S cells, nuclei and cytoplasm) and a decrease in the nuclear-cytoplasmic ratio by 0.6, respectively, which indicated a decrease in their functional potential. In some testicular cysts, globular clusters of cells were first detected, which were identified as spermatocytes of the 1-st and 2-nd order. Further differentiation of spermatocytes within the masses was in fact excluded, which was the main reason for gonadal sterility. Originality. The obtained data allowed characterizing previously unknown aspects of gamete maturation. A detailed consideration of the stages of abnormal spermatogenesis provides an opportunity to assess the reproductive potential of sterlet. Practical Value. The information obtained is valuable in morphophysiological studies and in ichthyological practice in connection with the existing problem of reducing the reproductive potential of fish under conditions of technogenic stress. The use of the obtained data allows substantiating the feasibility of environmental measures, which will allow assessing the state of the ichthyofauna and reducing the unjustifiably high load on spawners during the spawning migration period. Keywords: sterlet, gonads, spermatogenesis, cysts, spermatogonia, spermatocytes, interstitial cells, Sertoli cells, sterility.