seemingly adapted to a preferred prey (Tamm and Tamm, 1993). Beroe ovata occurs with M. leidyi as a prey in its native habitat along the eastern American coast (Mianzan, 1999; Purcell et al., 2001; Oliveira and Migotto, 2006). Beroe cucumis occurs with the prey species Bolinopsis; therefore, we do not know if native Beroe species will consume M. leidyi or not in the Adriatic Sea. We observed that native Beroe species tried to swallow individuals of M.leidyi but then spat them out, indicating that the native Beroe probably does not prey on M.leidyi.