The influence of water salinity on the distribution of myxosporeans of the genus Kudoa (Cnidaria, Myxozoa) among fish of the World fauna
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Abstract
The occurrence of myxosporeans of the genus Kudoa in fish living in waters of different salinity was studied. The work is based on own materials on fish myxosporeans collected in 1987–2021 (more than 12,000 specimens of about 100 species of fish in the basins of the Atlantic Ocean (Azov (Russia, Ukraine), Black (Russia, Ukraine, Turkey) and Mediterranean (Italy, Spain) seas, in the Central Eastern Atlantic (abeam Mauritania) and in southern latitudes off the coast of Africa (abeam of Namibia), in the waters of the northern (near Norway) and southern (abeam of Argentina) parts of the ocean, off the southeastern coast of the USA), the Indian Ocean (the coast of Yemen) and the Pacific Ocean (South China Sea (Vietnam) and the central part of open waters)). In total, 27 representatives of myxosporeans of the genus Kudoa were studied using original material, of which 19 were identified to species. All available literary sources and the Internet database Fishbase were also used. It has been established that of the 291 representatives of Kudoa fish hosts, 169 species are purely marine, 76 species can live in marine and brackish water environments, 42 species are euryhaline and can be found in both marine and brackish and fresh waters, and only 4 species are purely freshwater. Of the 128 Kudoa species, 117 (91.4%) were found in the marine zone of the World Ocean, 8 (6.3%) in its estuaries (7 species in marine fish, 1 species in a freshwater host), 3 (2.3%) in freshwater reservoirs. In 2008–2019 long-term studies of Kudoa nova Naidenova, 1975 were carried out in estuarine-type ecosystems off the coast of Crimea at the mouth of the river Chernaya and Karkinitsky Bay (Black Sea), as well as in Eastern Sivash (Azov Sea). A total of 2232 specimens of 11 species of gobies were examined. It has been established that the periodic desalination of some areas by the waters of rice paddies, as well as the constant presence of fresh water in the surface layer of the Chernaya river mouth did not cause a strong change in salinity (with the exception of the northern part of Eastern Sivash), which would be destructive for this species of parasite. However, K. nova was absent from gobies caught in 1998 in a significantly desalinated river Don Taganrog Bay of the Sea of Azov, and in 2011 as well as in the Bug and Vistula rivers when studying microparasites of gobies that spread from the northwestern part of the Black Sea along the Central Invasive Corridor. Our experiment testified to the negative influence of fresh water on the spores of this parasite, which were subjected to deformation and darkening under its influence with disruption of the shooting of the polar filament.