ИСТИНА

Phoronida is a phylum of marine invertebrates with worldwide distribution. There are 14 species of phoronids in world fauna nowadays, but this number may be larger according to last researches. In the present study, morphology and microanatomy of new phoronid species – Phoronis savinkini sp. nov. – from Gulf of Tonkin of the South China Sea is studied. Phoronids of new species form settlements with a high density on rocky ground, covered with soft sediment, at a depth of 2 meters. The epidermal collar at the base of tentacles is absent, so we refer studied species to the genus Phoronis. The lophophore has spiral shape with one coil. There are 154 (160) tentacles. Special reproductive glands in the lophophoral cavity are absent. Longitudinal muscle bundles are of bushy type. The maximal number of bundles is 49. Each metanephridium has strongly curved excretory canal and two funnels: anal (small) and oral (large). There are two giant nerves of 2-5 micrometers in diameter. Comparative analysis of morphological characters that are used in phoronid taxonomy has shown that the morphology of new phoronid species from the South China Sea is the most similar to the morphology of Phoronis hippocrepia Wright, 1856, which has two morphs – burrowing in hard ground and living in soft substrates. However, there are significant morphological differences between two species: a fundamentally different type of the lophophore, whose organization is the main taxonomic character in phoronids, a different type of organization of the excretory organs (including the structure of nephridial funnels), and the absence of reproductive glands in crone of tentacles in the new species. Cladistics analysis of phoronid taxonomic diversity shows that ecological division of phoronids into two groups (burrowing and living in the soft substratum) has the taxonomic sense. Burrowing and digging phoronids probably had branched long time ago. Muscle type and the number of branches of nephridial canal can be considered as main differences between two groups. In this research monophyly of genus Phoronopsis and paraphyly of genus Phoronis are shown. The assumption on secondary simplification of Phoronis ovalis has made. An idea about presence of separated clade including Phoronis pallida and Phoronis embryolabi is supposed.