[Phenomenon of obligate parthenogenesis in rotifer (Rotifera, Bdelloida)]

A comparative analysis of biological and morphological organization of obligate parthenogenous bdelloids and heterogonic monogononts clarifies the specificity of bdelloids' environmental adaptation and variability. It is shown that phenotypic polymorphism of bdelloids differs from that of monogononts. The heterogonic Monogononta are characterized by tremendous phenotypic diversity in body structure adapted to different biotopes in continental waters. This diversity is reflected also in structure of corona and mastax used as major criteria for definition of high range taxa (classes, orders). The polymorphism of bdelloids manifests itself in variability of tiny morphological structures connected with living in restricted volumes of water, mainly in terrestrial biotopes. Being isolated from other Rotifera at the first stages of evolution, bdelloids have been specialized for living under extremely unstable terrestrial conditions that led to the development of anhydrobiosis and loss of amphimixis. Variability of bdelloids is not connected with characters of high taxonomic ranks and has principally different nature in comparison with monogononts. Tempo of specialization seems to be slower in obligate parthenogenous rotifers than in heterogonic ones.