First data on predation of Eucypris mareotica (Crustacea, Ostracoda) in hypersaline waters

Abstract

Seed shrimp Eucypris mareotica is a widespread species and can reach high abundance in hypersaline lakes and lagoons of the Crimea and other regions. As an example, the maximum abundance of E. mareotica in the hypersaline Chersonesskoye lake reached 198,500 ind./m3 in the plankton, 580,000 ind./m2 in the benthos, and 220,000 ind./m2 in floating Cladophora mats. The species with such high abundance must play an important role in food webs but this role is not known now. Samples were collected from the different habitats in the lake to conduct gut content analysis of E. mareotica. The proportion of ostracods with food items in guts ranged from 9% to 100% in a sample. In 50% of them, animals found in ostracod gut contents include animals (Copepoda (Calanoida or/and Harpacticoida), Cladocera, or Nematoda). The most abundant food item was Cletocamptus retrogressus (Harpacticoida). Experiments with eggs, cysts and nauplii of Artemia (Anostraca) suggested that ostracods cannot break the cyst shells, but as soon as the nauplii hatched, they could be eaten by ostracods. Non-dormant (summer) Artemia eggs have weaker outer shells; ostracods break shell integrity with their antennae and then consume them. Animals play an important role in the diets of E. mareotica in the Crimean hypersaline lakes and lagoons, as can be assumed in other regions also.