Reproduction peculiarities in aboriginal species of anodontinae (Mollusca, Bivalvia) from Ukraine
Ivan Franko State University of Zhytomyr
40, Velyka Berdychivska St., Zhytomyr 10008, Ukraine
Reproduction cycles of Anodontinae aboriginal species collected in all river basins of Ukraine are studied. Terms of the beginning and the end of reproduction are established. The longest pregnancy is observed in P. complanata. The proportioning of oviposition is confirmed. Differences in reproduction calendar of the researched species are noted. Reproduction processes of Anodontinae from water reservoirs and streams of Unionidae proceed inadequately. It is assumed that the reason of such a phenomenon may be the low population density (up to 6 spp./m2) that prevents normal fertilization and the impact of aquatic environment pollutants, because all germ cells are extremely sensitive even to the low concentration of toxicants and will experience destructions in the gonad acini. In A. anatinŕ 100% of females reproduce only in 57% of collection points. In other points only 17–90% of females are pregnant, in A. cygnea – 50% of females. The decrease of individual fertility in researched species specimens is registered. Thus, in 70% of collection points A. cygnea and P. complanata females marsupia are filled partially (from ¼ to ¾) with sex products. The number of glochidia in P. complanata females is the lowest among Anodontinae.
Keywords: Anodontinae, reproduction, “branchial pregnancy”, marsupia