Chemical Analysis of the Luminous Slime Secreted by the Marine Worm Chaetopterus (Annelida, Polychaeta).

The marine annelid Chaetopterus variopedatus produces bioluminescence by an unknown and potentially novel mechanism. We have advanced the study of this fascinating phenomenon, which has not been investigated for nearly 60 years after initial studies were first reported for this species. Here, we show that the luminous slime produced by the worm exhibits blue fluorescence that matches the bioluminescence emission. This result suggests that the oxyluciferin emitter is present. However, while the blue fluorescence decays over time green fluorescence is increasingly revealed that is likely associated with products of the luminescence reaction. LC/MS and fluorescence analysis of harvested luminescent material revealed riboflavin as the major green fluorescent component. Riboflavin is usually associated with the mechanism of light production in bacteria, yet luminous bacteria were not found in the worm mucus, and accordingly were not reported to be directly responsible for the light emission, which is under nervous control in the worm. We therefore propose a hypothesis in which riboflavin or a structurally related derivative serves as the emitter in the worm's light producing reaction.