We describe a new vent mussel species, Gigantidas vrijenhoeki n. sp., from material collected at a depth of 2022 m in the newly discovered Onnuri Vent Field (OVF) during the 2018 expedition to the Central Indian Ridge. This large modioliform mussel thrives around diffusive vents in aggregation with another dominant hydrothermal vent mussel, Bathymodiolus marisindicus. G. vrijenhoeki n. sp. was distinguished from its neighboring B. marisindicus by its distinct shell profile, which consists of an elongated shell with a short and low anterior region, high expanded posterior region, and deep ventral concavity. Visually, the new mussel species resembles G. securiformis; however, it is clearly distinguished by several shell and anatomical features. Genetically, the new species is closely related to two undescribed Gigantidas species found in the cold seeps of the western Pacific. Phylogenetic analysis of G. vrijenhoeki n. sp. supports the connectivity of vent fauna between the Indian Ocean and the western Pacific in the past. To the best of our knowledge, this is the first record of a Gigantidas species in the Indian Ocean. In addition, we found gill-associated sulfur-oxidizing and methane-oxidizing bacteria, Gammaproteobacteria and Epsilonproteobacteria, symbionts present on this new species. Their composition was clearly different from symbionts found on the co-occurring B. marisindicus at the OVF. Notably, the sulfurovum-related Epsilonproteobacteria on the G. vrijenhoeki n. sp. were phylogenetically distinct from the family of Bathymodiolinae-related Epsilonproteobacteria. Taken together, the co-occurrence of two mussel species at the new vent field and their distinct gill symbiotic communities provides a useful setting in which to study the genetic connectivity of vent mussels along the Central Indian Ridge and the evolutionary dynamics between host mussels and symbionts.

我们描述了一个新的贻贝种类，Gigantidas vrijenhoeki n。物种，来自于2018年对中印度洋脊的考察中新发现的Onnuri通风场（OVF）中2022 m深度的材料。这种大型MODIoliform贻贝在扩散喷口周围繁衍生息，并与另一个优势热液喷口贻贝Bathymodiolus marisindicus聚集在一起。G. vrijenhoeki。sp。与它的邻近的马里氏乳杆菌（B. marisindicus）的区别在于其独特的壳轮廓，它由具有短而低的前部区域，高扩展的后部区域和深腹凹的细长壳组成。从外观上看，新蚌种与摹。securiformis; 但是，它的明显特点是具有多个外壳和解剖特征。从基因上讲，新物种与西太平洋冷渗漏中发现的两个未描述的巨人科物种密切相关。G. vrijenhoeki n。的系统发育分析。sp。支持过去印度洋和西太平洋通风口动物群的连通性。据我们所知，这是印度洋中硕大ig科鱼类的第一个记录。此外，我们发现了与ill相关的硫氧化和甲烷氧化细菌，丙种细菌和小肠细菌，共生体出现在这个新物种上。它们的组成明显不同于在OVF上同时出现的B. marisindicus上的共生体。值得注意的是，G。vrijenhoeki n。上与硫属有关的Epsilon变形细菌。sp。在系统发育上不同于嗜盐杆菌科的Epsilonproteobacteria。综上所述，两种贻贝物种在新的喷口场及其独特的g共生群落中共存，为研究沿中印度洋脊喷口贻贝的遗传连通性以及寄主贻贝和共生体之间的进化动力学提供了有用的环境。 。