Growth, demographic structure of population and determination of Bithynia tentaculata (Gastropoda, Prosobranchia) age [Russian]

摘要

The growth and population structure (age and sex) of Bithynia tentaculata (Linne 1758) were investigated in a pond of the "Sosnovka" park (St. Petersburg) over a period of six years. The maximal growth rate of B. tentaculata is observed during the first and second years of life. The growth of adults occurs in May-June, that of juveniles, froth their birth (June) up to September. The thickness, color; erosion, of the external, surface and microbiological fouling of B. tentaculata shells change regularly throughout a year and with age. At the end of each winter, B. shells bear the lines of growth interruption, similar to those in other gastropods. The unstable age structure in B. tentaculata found is caused by the high mortality of juveniles. The sex ratio in the,population of mollusks is about 1 : 1. The share of males increases to some degree with age,probably due to higher reproductive loads. The data obtained are considered with respect to the possibility of determining the Age of B. tentaculata according to "annual rings" on its shell.