ИСТИНА

Information on reproduction and development of 25 species of onuphid polychaetes was summarized based of published data. Gametes and developmental patterns in Mooreonuphis stigmatis and Leptoecia vivipara, species representing two monophyletic subfamilies of onuphids, were studied utilizing methods of light microscopy, histology, SEM, TEM and cLSM. M. stigmatis was collected from intertidal mud flats in the north-eastern Pacific. Females bear large yolky eggs with two attached strings of nurse cells in the posterior segments. Males have spermatozoa with very long nuclei, conical acrosomes and relatively short flagella developing in the coelomic cavity. Genital segment of females bear dorsal seminal receptacles – organs of sperm storage. Lecithotrophic larvae develop inside the parental tubes. Up to three hatches with about 20–30 broods can be found in a single female tube. Larvae in every hatch develop synchronously and are released to the environment at a stage of 18–20 chaetigers. A number of brooding specimens of L. vivipara were found at several deep-sea sites around Antarctic. Presumable females have paired serial ovaries in the anterior segments and may bear up to 12 broods inside the coelomic cavity of the mid body region. Development of broods is asynchronous; each brood represents a consecutive stage from unfertilized oocyte with a cap of nurse cells to a well developed juvenile with up to 13 chaetigers. No male gametes were observed in L. vivipara. Both analysed species display reduction of trochal ciliation in the developmental stages, replacement of provisional chaetae by definitive chaetae and at least three types of consecutive sets of maxillae differing in morphology and number of plates and replacing each other during the development. Two general patterns of chaetal replacement characteristic for two onuphid subfamilies were described.