ИСТИНА

Patterns of oogenesis and spermatogenesis reflect reproductive biology of animals, which have variable life cycles, modes of fertilization and development. The oogenesis dependents on type of larval development (e.g. lecitotrophic or planktotrophic); spermatogenesis and spermatozoon structure correlate well with certain type of fertilization (e.g. external or internal). The gametogenesis patterns and gamete morphology are widely used for analysis of taxonomy and phylogeny of different invertebrate taxa. To elucidate the phoronid relationships amongst other bilaterian we investigated the gamete morphology and development, the spermatophore and the lophophoral organ organization in Phoronopsis harmeri. Phoronids lack true gonads; the germ cells develop inside the coelothelium derived, which is called vasoperithoneal tissue. The phoronids demonstrate the combination of morphologically clear follicle oogenesis with distinct autosynthetic vitellogenesis. The spermatozoon maturation terminates in spermatophores forming inside paired lophophoral organs, each of which consists of the lower sack-like and the upper hood-like parts. The floating spermatophores have a spiral sail. The spermatozoon is V-shaped where a half of the cell is flagellum and opposite half contains nucleus and mitochondrion; the acrosome is positioned at the point of the flexure. The organization of spermatozoon correlates well with the internal fertilization. Despite unusual deviations in spermatozoon organization, the phoronid spermatogenesis can be regarded as primitive “flagellate type”. Phoronids demonstrate a series of primitive features in their gametes and gametogenesis, which include also some specialized characters. This work was supported by RFBR grants 11-04-00690 and 12-04-33045.