Epibionts and parasites on crustaceans (Copepoda, Cladocera, Cirripedia larvae) inhabiting the Gulf of Gdańsk (Baltic Sea) in very large numbers*

The occurrence of epizoic filter-feeding Protozoa (Vorticella and Zoothamnium) and parasitic Protozoa (Ellobiopsis) on Calanoida was noticed in the Gulf of Gdańsk in 1998, 1999 and 2006. The relatively high (4–16% of all calanoids) level of infestation varied depending on the type of infestation (0.1–13% of the population of particular taxa). The dominant copepods – Acartia spp., Temora longicornis and Centropages hamatus – were attacked the most frequently (from 10.5% to 54% of all infested calanoids). Epibiosis and parasitism were observed on all copepod developmental stages (adults, juveniles and nauplii). Epibionts and parasites were located on different parts of the body, but mainly on the prosome.Infestation by epibionts and parasites was not restricted to calanoid copepods: it was also detected in non-negligible numbers on other crustaceans, namely, Harpacticoida, Cladocera (Bosmina sp.) and Cirripedia larvae (nauplii) in the Gulf of Gdańsk.