Abstract <p>The first finding of the boring polychaete <i>Dodecaceria concharum</i> in the shells of the Icelandic scallop <i>Chlamys islandica</i> from the Barents Sea is reported. The species identification of the polychaete was established using molecular genetic analysis. It was found that the polychaetes form Y-shaped passages in the shells of the mollusks in the overwhelming majority of cases, which can lead to a violation of the integrity of the shell and a decrease in their physiological activity. An association was found between the polychaete infestation and the presence of boring sponges of the genus <i>Cliona</i>, indicating a complex destructive effect on mollusks. The results obtained emphasize the need for further research into the dynamics of infestation of the scallop and assessment of its consequences for the commercial population.</p>