The ostracod Cyprideis torosa (Jones) tolerates a wide range of salinity from fresh to brackish water-transition to hyperhaline values. The species often dominates ostracod assemblages in oligohaline and hyperhaline waters. For a more precise determination of controlling ecological factors, mainly the salinity, the accompanying ostracod fauna needs to be investigated. In oligohaline inland water bodies of humid climates, C. torosa is associated with tolerant non-marine ostracods. In coastal lagoons the mostly very low-diversity ostracod assemblages are characterized by brackish taxa accompanying C. torosa. In saline lakes of arid climatic zones non-marine and brackish species occur together, but brackish ostracods frequently dominate the assemblages. Monospecific occurrences of C. torosa are realized mainly in hypersaline environments. Examples are given that represent typical ostracod taxa that co-occur with C. torosa.