Deep-sea cold seeps are dynamic sources of methane release and unique habitats supporting ocean biodiversity and productivity. Here, we describe newly discovered animal-bacterial symbioses fueled by methane, between two species of annelid (a serpulid Laminatubus and sabellid Bispira) and distinct aerobic methane-oxidizing bacteria belonging to the Methylococcales, localized to the host respiratory crown. Worm tissue δ¹³C of −44 to −58‰ are consistent with methane-fueled nutrition for both species, and shipboard stable isotope labeling experiments revealed active assimilation of ¹³C-labeled methane into animal biomass, which occurs via the engulfment of methanotrophic bacteria across the crown epidermal surface. These worms represent a new addition to the few animals known to intimately associate with methane-oxidizing bacteria and may further explain their enigmatic mass occurrence at 150–million year–old fossil seeps. High-resolution seafloor surveys document significant coverage by these symbioses, beyond typical obligate seep fauna. These findings uncover novel consumers of methane in the deep sea and, by expanding the known spatial extent of methane seeps, may have important implications for deep-sea conservation.

深海冷渗漏是甲烷释放的动态来源，也是支持海洋生物多样性和生产力的独特栖息地。在这里，我们描述了新发现的动物细菌共生体，由甲烷驱动，介于两种种类的肘突动物（一种蛇足类植物的laminatubus和sabellid Bispira）和属于甲基球菌的独特的需氧甲烷氧化细菌之间，位于宿主的呼吸冠上。蠕虫组织δ ¹³的-44℃至-58‰的甲烷为燃料的营养两个种类，和船上的稳定同位素标记实验揭示了一致主动同化¹³C标记的甲烷转化为动物生物质，这是通过甲烷营养细菌在冠状表皮表面的吞没而发生的。这些蠕虫是已知与甲烷氧化细菌密切相关的少数动物的新成员，并且可能进一步解释了它们在1.5亿年前的化石渗漏中的神秘质量。高分辨率的海底调查表明，除了典型的专一性渗漏动物群以外，这些共生生物还覆盖了很多生物。这些发现揭示了深海甲烷的新消费者，并且通过扩大甲烷渗漏的已知空间范围，可能对深海保护具有重要意义。