Salinity as a Factor Limiting the Crustacean Potential Taxonomic Richness in the World’s Hypersaline Water Ecosystems: a Review

Crustaceans are one of the biosphere’s most diverse and successful groups, also inhabiting various extreme habitats. Summing up our data and 203 literary sources, we analyzed how the degree of environmental extremeness can limit the potential taxonomic richness of crustaceans using the example of hypersaline waters. An analysis showed that, with an increase in salinity, the number of classes and orders of the Crustacea subtype decreased linearly, while the number of genera and species decreased exponentially. It has been established that with an increase in environmental salinity, the contribution of Arthropoda species to the total species richness of animals in hypersaline waters increases from 49 to 100%, the gift of Crustacea species to the total species richness of Arthropoda increases from 66 to 78%, and the contribution of Branchiopoda to the species richness of Crustacea from 19 to 71%. In the Crimean hypersaline water bodies, in the range from 35 to 120 g/L, salinity is not the main factor determining the species richness and composition of the fauna, the combination of all other factors, primarily biotic ones, plays a more critical role. Only at higher values, salinity itself begins to play the role of a hard-environmental filter. Salinity growing above 35 g/L reduces the comfort of the environment for animals and filters out the pool of species that can exist in the ecosystem. In particular water bodies, the realization of this possibility depends not only on salinity but also on the existing biotic relationships and the entire set of abiotic factors.