HISTORY OF FORMATION OF THE FAUNA OF THE FISH MYXOSPOREA OF THE WATER BODIES OF AZERBAIJAN

Despite the fact that all water bodies of Azerbaijan belong to the basin of Caspian Sea, among the myxosporeas of our fish, there are only 3 species from Ponto-Caspian marine faunistic complex formed by brackish-water of Pontic Lake-Sea. In the Neogene, in the drainless water bodies of Near East, Western Asian faunistic complex arose. Its representatives began to penetrate into the water bodies of Caucasus, after it joined its southernmost tip to the mainland and turned from an island into a peninsula. From the myxosporeas of our fauna, this complex includes species that parasitize mainly on Labeobarbus and barbel. In the Neogene, in the water bodies of Northern Palaearctic, the most widespread freshwater faunistic complex, i.e. boreal plain complex (in the sense of Yakovlev, 1964) was formed. In our fauna, it is represented by three environmental groups. From these, palearctic group includes specific myxosporea of northern pike and a number of species with a wide range of hosts. Representatives of the next, Ponto-Caspian group are inferior to the Palaearctic species in the degree of eurythermy and are therefore more numerous in the southern and low-land areas than in the northern and mountainous. Among the myxosporeas of the fauna of the republic there are 16 of them. They are found in fish belonging to various faunal complexes. Our amphiboreal group consists of 6 species with interrupted habitat, including Europe and the Far East. The vast majority of myxosporeas of boreal low-land origin is euryhaline and can parasitize in the body of many fishes. Therefore, these forms could easily penetrate from the north, for example, from Volga basin, into the brackish waters of the Caspian Sea. Passing the sea, through rivers, on migratory fish, they also got into the freshwater bodies of our region. Due to periodically occurring phases of desalination, this process has been significantly simplified. In Neogene, when the mountain range of the Greater Caucasus did not reach its present height, boreal forms could pass into the freshwater bodies of the Caucasus also through the upper reaches of the rivers. In the era of productive strata, as a result of strong regression, the northern boundary of the sea water body corresponding to modern Caspian Sea receded far to the south and the rivers flowing now into the Middle Caspian Sea temporarily turned into tributaries of the so-called Paleo-Volga. In such conditions, typically freshwater boreal forms of the fish and ichthyoparasites penetrated the southern freshwater tributaries.

Approximately in the Neogene, in the lowlands of Palearctic, a brackish-water faunistic complex was formed, in particular, sticklebacks and their highly specific parasites, including 3 species of myxosporidia. Their penetration into our region could follow the same paths as boreal lowland forms. Moreover, given the limnophility nature of the former, apparently, the possibility of their crossing the upper reaches of the rivers should be excluded.

In the post-tertiary period, when the Khvalyn (Caspian) basin renewed its connection with the Ancient Euxin (Black Sea) basin, the entrance of the Mediterranean into atherins, Common goby and pipefish, as well the latter parasite, myxosporea Sinuolinea sakinachanumae was happened in the Caspian Sea.

Salmon fish and 2 species of their myxosporeas in the water bodies of Azerbaijan are representatives of boreal piedmont-faunistic complex, which formed in Siberia and Northern Europe from some of boreal low-land part. Their penetration, apparently, should be attributed to already post-glacial period, when the nelma moved into the Caspian Sea from the Arctic basin, which then turned into a passage inconnu.