Sexual reproduction and mating system of the diatom Tabularia tabulata were studied in clonal cultures. Cw-type anisogamous sexual reproduction was revealed. Mating system involves homo- and heterothallic modes of reproduction; and both male and female clones are capable to reproduce hornothallically. The combination of homo – and heterothallic modes of reproduction gives certain evolutionary advantage; on the one hand, providing homozygous lines, and on the other hand, increasing genetic diversity. Study of sex inheritance in the first generation progeny revealed the nature of sex determination in T. tabulata. Male sex is heterogametic resulting from the presence of two alternative genetic factors, condi tionally M and F, while female is homogametic and determined by combination of FF sexual factors.

Keywords: Tabularia tabulata, sex inheritance, sexual reproduction, mating system

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