Fertilization of freshwater fish occurs in the environment which negatively affects a lifespan of gametes mostly due to the osmotic shock; therefore, male gametes should reach the female gamete, as soon as possible. The existence of mechanisms controlling the encounter of gametes would be highly expedient in this case. By analogy with other species for which guidance was demonstrated, it is likely that this control may be performed by ovarian fluid or substances released by eggs. The aim was to study the effect of ovarian fluid and egg-released substances on spermatozoa behavior in sterlet. It was found that the presence of a particular concentration of ovarian fluid (30% solution in water) had an inhibiting effect on spermatozoa motility initiation. Lower concentrations of the ovarian fluid improved the longevity of spermatozoa and did not affect their trajectories. Test of chemotactic response (using a microcapillary injection of fluids into the suspension of motile spermatozoa) showed no effect of ovarian fluid on spermatozoa behavior, while at the same time, the attracting effect of the egg-conditioned medium was evident (i.e., due to some substances released from the eggs during their contact with freshwater). The results of the fertilization test showed that the presence of ovarian fluid prevented the eggs from losing the fertilizing ability due to the contact with water, as well as promoted the spermatozoa to fertilize the eggs during a longer period of time. Thus, the combined physicochemical action of “female factors” affects sterlet gametes during fertilization and may be involved in the guidance and selection mechanisms.

淡水鱼的受精发生在主要由于渗透休克而对配子寿命产生负面影响的环境中；因此，雄配子应尽快到达雌配子。在这种情况下，控制配子相遇的机制的存在将是非常有利的。通过与其他已证明有指导作用的物种进行类比，这种控制可能是由卵巢液或卵子释放的物质进行的。目的是研究卵巢液和卵子释放物质对雌性精子行为的影响。发现特定浓度的卵巢液（30% 水溶液）的存在对精子运动的启动具有抑制作用。较低浓度的卵巢液可以延长精子的寿命，并且不会影响它们的运动轨迹。趋化反应测试（使用微毛细管注射液体到活动精子悬浮液中）显示卵巢液对精子行为没有影响，同时，卵条件培养基的吸引作用很明显（即，由于鸡蛋与淡水接触时会释放出一些物质）。受精试验结果表明，卵巢液的存在可以防止卵子因与水接触而失去受精能力，并促进精子在更长的时间内对卵子受精。因此，