ИСТИНА

Condao islands are the archipelago lie ca. 100 km of the South Vietnam. Human impact on marine ecosystems was restricted here since long ago till recently. All the intertidal communities look rather intact. Nematodes were collected there in several locations on two islands; each set of samples includes one taken from the rhizosphere of dominated mangrove trees and the next from outside the mangroves, on the bare calcareous sand on reef-flat. Local species diversity was estimated in each location to test the hypothesis of the reduction of species number in insular ecosystems. Second set of tests was provided to evaluate the differences between nematodes assemblages in vicinity of mangroves roots and outside. The results of this test highlight the role of mangroves and their roots as a structuring factor for the communities of free-living nematodes. For the first time species diversity and communities composition was described for the islands of the region. Species diversity of the free-living nematodes was comparable with the figures obtained in the same habitats of the mainland. The commonalities in species composition were found in mangroves and reef-flat sediments; several genera (Ptycholaimellus, Tershellingia, Anoplostoma) and families, such as Desmodoridae and Stilbonematidae, are typical form mangrove rhizosphere and assume to be mangrove-associated. (Support: RFBR 21-54-54006). – 1P.P. Shirshov Institute of Oceanology RAS, Moscow, Russia. E-mail: vadim@ocean.ru; 2Moscow State University, Biological Dept., Moscow, Russia; Institute of Ecology and Biological Resources, Department of Nematology, Hanoi, Vietnam.