Terebellidae worms have large numbers of tentacles responsible for various biological functions. Some Terebellidae worms whose tentacles emit light are found around the world, including exceptional violet-light-emitting Polycirrus spp. found in Europe and North America. However, there is no video-recorded observation of the luminous behavior of such unique species in nature, and the genetic information related to their ecology are lacking. Here, for the first time, we video-recorded the violet-light-emitting behavior of an undescribed Japanese worm in its natural habitat. The worm was designated as Polycirrus sp. ISK based on morphological observations, and the luminescence spectrum showed a peak at 444 nm, which is an exceptionally short wavelength for bioluminescence in a shallow coastal water environment. An analysis of differentially expressing genes based on separate RNA-Seq analysis for the tentacles and the rest of body revealed the specific expression of genes that are probably involved in innate immunity in the tentacles exposed to predators. We also found a Renilla luciferase homologous gene, but coelenterazine was not detected in the worm extract by analyses using a liquid chromatography and a recombinant Renilla luciferase. These results will promote an understanding of the ecology and luminescence mechanisms of luminous Polycirrus spp.

特雷贝科蠕虫有大量的触手，负责各种生物功能。世界各地都发现了一些触手发光的Terebellidae蠕虫，其中包括特殊的发出紫光的Polycirrus spp。发现于欧洲和北美。然而，自然界中并没有对这种独特物种的发光行为进行视频记录观察，也缺乏与其生态相关的遗传信息。在这里，我们第一次用视频记录了一种未描述的日本蠕虫在其自然栖息地中发出紫光的行为。该蠕虫被命名为Polycirrus sp。 ISK基于形态学观察，发光光谱在444 nm处出现峰值，这是沿海浅水环境中生物发光的极短波长。基于对触手和身体其他部分的单独RNA-Seq分析，对差异表达基因进行了分析，揭示了暴露于捕食者的触手中可能与先天免疫相关的基因的特异性表达。我们还发现了海肾荧光素酶同源基因，但通过使用液相色谱和重组海肾荧光素酶进行分析，在蠕虫提取物中未检测到腔肠素。这些结果将促进对发光多卷菌属的生态和发光机制的理解。