Crustaceans of the Aral Sea

— Based on the literature and studies carried out by the authors over more than 30 years, an analysis of the fauna of crustaceans of the Aral Sea is presented. The faunal composition, the changes that have taken place since the 1950s, and the relations to the salinity factor are considered. Crustaceans in the Aral Sea make up about one-quarter of the species diversity of Metazoa. They are represented by freshwater, brackish water, and marine species, as well as halophiles from saline continental waters of the arid zone. The first changes in the composition of the crustacean fauna of the Aral Sea started even before its modern regression. They were the result of deliberate, as well as accidental, introductions of a number of initially absent species of invertebrates and fish. Since the 1960s, the main cause has become the rapid change in salinity. As the salinity has increased, the species diversity of the crustaceans has sharply decreased due to extinction, first of freshwater and then of brackish water species. After the level of the Aral Sea fell and it was divided into two parts, the Small Aral and the Large Aral, further evolution of these residual water bodies proceeded in different directions. As a result of the construction of the dam in the former Berg Strait, it became possible to decrease the salinity of the Small Aral Sea and gradually restore the crustacean fauna. The Large Aral has now turned into a hyperhaline water body inhabited by only a few species of crustaceans.