ИСТИНА

Organization of the lophophore is an important point in frame of the problem of the lophophorates monophyly. Although the lophophorates monophyly was supported by anatomical and embryological data and by few results of molecular phylogeny, most of molecular data reject the unity of the lophophorates because of specific phylogenetic position of bryozoans. The detailed investigation of the lophophore, which is the morphological peculiarity of the lophophorates, may help to clarify question of the lophophorates monophyly. Neuro-muscular system of the lophophore was investigated in four phoronid species with different types of the lophophore organization: Phoronis ovalis, Phoronis ijimai, Phoronis australis, Phoronopsis harmeri. Comparative analysis of new data revealed that the simplest lophophore of tiny P. ovalis is innervated by more numerous nerves than complex lophophores of other studied phoronid species. Nervous system of P. ovalis lophophore consists of the dorsal ganglion, the tentacular nerve ring, the inner nerve center, and the inner nerve ring, which gives rise to the frontal and laterofrontal tentacular nerves. Serotonin-like immunoreactive flask-like cells are located on inner nerve ring between tentacles at their base. The presence of these cells, peculiarities of innervation of tentacles, and the presence of the inner nerve ring make the nervous system of the lophophore of P. ovalis different from the nervous system of the lophophore of other adult phoronids and similar to the nervous system of the lophophore of bryozoans. This similarity allows to regard P. ovalis as a connecting link between phoronids and bryozoans. Project is supported by RFBR (17-04-00586).