Abstract
The paper reports the range extension of the Ponto- Caspian gammarid Dikerogammarus villosus (Sowinsky, 1894) and the first occurrence of this species in new areas of the Polish part of the Baltic Sea basin: the Śmiała Vistula and the Vistula Lagoon.
The studies additionally determine the osmoregulatory ability of the species under laboratory conditions within the salinity range of 2-22 PSU. Determination of the osmoregulation of the species shows that D. villosus is a hyperregulator at given experimental salinities and can function in a wide range of external salinities so it is potentially able to colonize various water bodies. Osmoregulatory capacity, which is an indicator of organism’s efforts to regulate the concentration of its body fluids, shows that for individuals from the Gulf of Gdańsk, 6 PSU is the best tolerated salinity. Osmoregulatory capacity is the lowest at this salinity value.
The range extension and potential osmoregulatory abilities of the species to spread to other waters are discussed in the context of pollution levels given in the literature with reference to the habitat and sensitivity of the species to e.g. fluoride and cadmium toxicity.