Acineta nitocrae: A new suctorian epizooic on nonindigenous harpacticoid copepods, Nitocra hibernica and N-incerta, in the Laurentian Great Lakes

Acineta nitocrae, a suctorian ciliate previously known from Ukraine, was di scovered in western Lake Erie in October 1997 and in the Detroit River in M ay 1999. Individuals were found inhabiting the body surface of Nitocra hibe rnica and N. incerta, nonindigenous harpacticoid copepods. Acineta nitocrae infested 64% of N. hibernica in Lake Eric, whereas in Ukraine it infested between 24 and 80% of N. hibernica populations. In Lake Erie, N. hibernica copepods suffered lower suctorian burdens than conspecific individuals in n ative habitats in Ukraine. In Ukraine, this suctorian was also found on two other harpacticoid species-Nitocra lacustris and Canthocamptus staphylinus . The highest preference of A. nitocrae was established for N. hibernica. A cineta nitocrae individuals from Lake Erie and Ukrainian populations of N. hibernica were similar with respect to dimensions of the lorica and stalk, but differed significantly in terms of the length and width of actinophores , with highest values observed for Lake Erie. Occurrence of A. nitocrae in the Great Lakes may be related to the introduction of its hosts, N. hiberni ca and N. incerta.