The species of the genus Ophryodendron are epibionts of various invertebrate animals. They are rarely found in nature, and very little research has been dedicated to them recently. Ophryodendron abietinum, an epibiont of a hydrozoan Obelia longissima, was discovered in the White Sea for the first time. This study provides a description of O. abietinum life cycle forms and host-epibiont interactions.