ИСТИНА

The Sarmatian basin existed 10.5-14 mln years ago and included modern water areas of the Black, the Azov, the Caspian and the Aral Seas. After its breakup 5-7 mln years ago, the newly formed seas/lakes had different history of hydrology and ecosystems development. The present article is conserned with the Harpacticoida fauna of the Caspian Sea: its structure, dynamics and biogeographical relationships. On the basis of the original materials collected in the Southern and Northern Caspian Sea the harpacticoids fauna and the taxocenes structure was described. One third of the found species is new for the region, and 3 species are new for science. Endemics make up 24% of the total species number, while cosmopolitans and widely boreal species compose 38% each. The seasonal and interannual dynamics of harpacticoida from littoral zone of the Southern Caspian (Azerbaijan) was studied. It is shown that because of instability (sporadic alternation of warm and cold winters) of maritime climate there is no pronounced seasonal periodicy of species complexes in the littoral zone of the investigated coast. A comparative analysis of the faunas of the Aral, Caspian, Black and Mediterranean Seas was performed. All areas are clearly divided into two distinct blocks: the Mediterranean and the Sarmatian, which indicates the relationship between faunas of the fragments of the previously single relict Sarmatian Sea basin. However, the environmental characteristics of the harpacticoid faunas in the seas, fragments of the Sarmatian Sea, vary considerably. The fauna of the Caspian Sea (salinity 12 ‰), which keeps the Sarmatian features the most, consists mainly of brackish species (59% of the total), a quarter of the fauna is represented by endemics, while the marine species are few (17%). The Aral Sea, shallowed dramatically over the last century, has passed to the category of hypersaline (100 ‰). In this connection, the previously reported 15 Harpacticoida species are not found in the sea anymore. Fauna of the desalinated (11 ‰) Azov Sea, which has connection to the Black Sea, is a mix of freshwater and brackish species (65%), with inclusions of marine species (35%), which regularly migrate from the Black Sea. Endemic species are absent in the Azov Sea because of the high versatility of the conditions in it historically. The Black Sea connected with the Mediterranean Sea has a salinity of 22 ‰. Its fauna consist mostly of marine species (80%) and about a quarter of the species are endemics. Thus, because of the different hydrochemical conditions, the Caspian, Aral, Azov and Black Seas vary considerably in the structure of Harpacticoida fauna currently. However, this water areas are united by a numerous group of brackish species, which probably formed the main part of the harpacticoida fauna in Sarmatian basin previously.