Bioluminescent properties of Mesochaetopterus japonicus (Polychaeta: Chaetopteridae) with comparison to Chaetopterus

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Mesochaetopterus is a bioluminescent polychaete that belongs to the family Chaetopteridae. It secrets a blue luminescent mucus as a response to mechanical stimulation similar to the species in Chaetopterus (Chaetopteridae). However, unlike Chaetopterus, the biochemical properties of Mesochaetopterus bioluminescence are largely unexplored. In this study, we examined the basic biochemical properties of the bioluminescence seen in Mesochaetopterus japonicus and compared them to those seen in Chaetopterus. The comparison revealed that similar blue luminescence peaked at approximately 460 nm were induced by the addition of Fe²⁺ and H₂O₂, suggesting that bioluminescence in M. japonicus and Chaetopterus has similar basic biochemical properties. On the other hand, the gel filtration analyses showed that the elution volumes of active proteins were different between Mesochaetopterus and Chaetopterus. The molecular weights of these proteins were estimated to be 150 kDa and 90 kDa (approximately) for Mesochaetopterus and Chaetopterus, respectively.