Artemia spp. play a key role in hypersaline ecosystems. Artemia can live in a salinity range from 10 to 300-340 g/L, but in water bodies where salinity is between 10 and 100 g/L, it may be absent. Is the absence of Artemia in some Crimean lakes determined by the presence of predators or by salinity? To answer this question field long-term and experimental data collected in the Crimean lakes were used. With the least probability, the populations of Artemia existed in the lakes with a salinity of up to 50 g/L or above 300 g/L. Self-reproducing Artemia populations (all age stages) were most likely (≥80% of occurrence) noted in the salinity range of 150-200 g/L. Longterm monitoring in two lakes showed that in different years, a significant negative correlation of Artemia abundance with the numbers of amphipod Gammarus aequicauda and ostracod Eucypris mareotica was found in both lakes. This correlation can be explained by ostracod and amphipod predation on Artemia. In years without predator populations, the number of Artemia was higher by several times.Experiments showed that these amphipods and ostracods consume brine shrimps of different developmental stages. There are at least 12 crustacean species, 5 insect species, and 2 fish species, all listed in this paper, which inhabit Crimean hypersaline waters and can eat Artemia. Their predation on Artemia often is a main cause of its absence in the salinity range from 10 to 150 g/L.
The Black, Azov, and Caspian sea drainages (i.e., Ponto-Caspian region) have an extensive and long history of species introductions. Here we review patterns and mechanisms of introductions of aquatic invertebrate species into these ecosystems. Since the late 1800s, 136 free-living and 27 parasitic invertebrate species have been introduced outside their native ranges and have established reproducing populations in the Ponto-Caspian region. The bulk of these introductions are represented by crustaceans (53%), flatworms (15%), and molluscs (13%). Most of the introduced species are native to other areas within the Ponto-Caspian region (37%), with other sizable contributions from the AtlanticMediterranean (15%) and boreal EuropeanSiberian (14%) geographic regions. Mechanisms of introductions were dominated by deliberate releases (29%) and shipping activities (22%), with the former occurring principally in freshwater habitats and the latter in marine and estuarine ones. Other introductions resulted from unintentional release (21%) and hydrotechnical development (14%), notably the construction of reservoirs and canals. Global and regional trade, particularly that mediated by commercial ships, provides dispersal opportunities for nonindigenous invertebrates to and within the Ponto-Caspian region, rapidly changing the composition of its endemic fauna.
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