Coelenterazine-dependent Bioluminescence in the Cyclopoid Copepod, Triconia conifera

Species in the cyclopoid copepod Triconia are known to be bioluminescent, emitting blue light by mechanical stimulus. In this study in Triconica conifera, we identified the presence of luciferase activity to coelenterazine, a substrate for the bioluminescence in various marine taxa such as luminous cnidarians, fishes, and crustaceans including calanoid copepods. The molecular size estimated by gel-filtration chromatography and pH dependency of the luciferase activity were similar to those in calanoid copepods. On the other hand, the reaction rate and inhibitory effect by magnesium ion were much different between them. The presence of coelenterazine in the specimen was confirmed by LC-ESI-MS/MS. Taken together with the phylogenetically distant relationship between Cyclopoida and Calanoida, our findings suggested that coelenterazine-dependent bioluminescence was evolved parallelly at least twice in copepod lineages.