Evadne anonyx G. O. Sars, 1897 – the first record of this Ponto-Caspian cladoceran in the Gulf of Gdańsk (Baltic Sea)*

Evadne anonyx, a new invasive Ponto-Caspian species, was detected for the first time in the Gulf of Gdańsk in the summer of 2006. Seven years probably elapsed from the first record of E. anonyx in the Baltic Sea (Gulf of Finland) to the first one in the Gulf of Gdańsk. Although the species was found at 10 out of 13 stations in rather low densities (not exceeding 6 indiv. m− 3), all the developmental stages of E. anonyx were present (juveniles as well as adults – parthenogenetic females, gamogenetic females and males) in the plankton material investigated.