A new symbiotic species of liljeborgiid amphipods, Liljeborgia associata sp. nov., is described from the burrows of the spoon worm Urechis unicinctus (Drasche, 1880) (Annelida: Polychaeta: Echiura: Urechidae) in the southern part of Peter the Great Bay and Posjeta Bay in the Sea of Japan. The new species is mostly similar and probably related to Liljeborgia geminata Barnard, 1969, known from the Californian coasts of the USA, and Liljeborgia serratoides Tzvetkova, 1967, described from Posjeta Bay in the Sea of Japan, but can be clearly distinguished from all congeners by morphological features of mouthparts, appendages and telson. The new species is only the fourth in the family Liljeborgiidae to be described from the Russian coast of the northwestern Pacific and the first in association with spoon worms (Echiura).
Diversity, association, northwestern Pacific, boreal, barcoding