ON THE NERVOUS SYSTEM OF A PARASITIC CNIDARIAN POLYPODIUM HYDRIFORME
E.V. Raikova
Institute of Cytology RAS, St. Petersburg;
e-mail: ekaterina.raikova@gmail.com
Nerve cells in a parasitic cnidarian Polypodium hydriforme at the parasitic and free-living stages of the life cycle have been localized immunocytochemically using antibodies to
FMRF-amide, and their ultrastructure has been described. Ganglion cells form a net under epidermis consisting of bi- and tripolar neurons which cross the mesoglea and usually
contact muscle cells and cnidocytes. Fusiform sensory and neurosecretory cells, especially characteristic to sensory tentacles, are interspersed among epidermal cells. All three types
of nerve cells have dense cored vesicles about 80-120 nm in diameter. The sensory cells demonstrate a sensory flagellum-like immobile structure. Neurosecretory and sensory cells
form septate junctions with epidermal cells. Ganglion cells show gap junctions between them. A centriole encircled by a fragment of nuclear envelope which is a marker of ectodermal
lineage cells in Polypodium has been described in the cytoplasm of a sensory cell, thus proving the ectodermal nature of the nervous system.
Key words: Polypodium hydriforme, cnidarians, nerve cells, neurosecretory granules, FMRF-amide, confocal microscopy, electron microscopy
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