A bioluminescent deep-sea polychaete within the genus Aricidea (Paraonidae) from Minamidaito Island, Japan

The phylum Annelida encompasses a diverse group of animals, with bioluminescent species documented in 14 families. Despite this diversity and the scattered distribution of bioluminescent lineages, little is known about the molecular biology, chemistry, morphology, ecology, and evolution of bioluminescence in annelids. During a deep-sea exploration off Minamidaito Island in the western Pacific Ocean, we discovered that Aricidea sp. emits green light when stimulated. The specimens were identified with the limited key morphology as a species in the genus Aricidea. A molecular phylogenetic analysis suggests that the specimen belongs to the Aricidea/Paraonis clade but was not nested in the described species, of which sequences were publicly available. This study is the first to report bioluminescence within the family Paraonidae.