THE SEXUAL STRUCTURE AND TERMS OF REPRODUCTION OF DREISSENA POLYMORPHA PALLAS, 1769 (MOLLUSCA: BIVALVIA: DREISSENIDAE) IN ZHITOMIR RESERVOIR

The sexual structure and terms of reproduction of Dreissena polymorpha, Pallas, 1769 in Zhytomyr reservoir are considered on the basis of the analysis of materials for the autumn-summer period 2014-2015. The dates of the onset of puberty and the age at which the mollusk is most intensively propagated are set. The stages of maturity of the gonads, their features and calendar terms are determined. It is established that the minimum size of mature molluscs is 8 mm., All the molluscs become mature at in size in11 mm. In the settlements of the investigated area, the ratio of males to females is characterized by the predominance of females. The period of breeding of the Dresena in the investigated reservoir lasts from the second decade of June to the first decade of September, the mass spawning is from the third decade of July to the first decade of September.