Ever since the first observations in the late 1960s, Cycliophora were found exclusively living epizoically on lobsters belonging to the family Nephropidae. The complex cycliophoran life cycle, with alternation of asexual and sexual generations, takes place only in the microhabitat provided by the host mouthparts. Herein, we report the first evidence of a symbiotic relationship between cycliophorans and organisms other than nephropid lobsters, namely, the harpacticoid copepods. Two specimens of copepods associated with cycliophoran life cycle stages were collected from the segmental mouthparts of a European lobster, Homarus gammarus. One of the copepods carried two feeding stages with long stalks, which probably belong to an undescribed Symbion sp., while the other copepod was found bearing an undetermined settled stage. We discuss the implications of these novel observations for the understanding of the Cycliophora life cycle and their dispersion abilities
