On the diversity of ‘bone-eating’ worms (Annelida: Siboglinidae: Osedax ) and their symbionts around the Iberian Peninsula

Annelid worms of the genus Osedax (family Siboglinidae), commonly known as ‘bone-eating worms’, are vertebrate bone specialists. They lack mouth, anus, and gut, and rely on an obligate symbiosis with bacteria capable of digesting the organic matter retained inside the bones. Since their discovery almost two decades ago, 34 different species have been named, occurring across all oceans. In this study we used experimentally deployed cow and pig bones at different depths (90–1200 m) around the Iberian Peninsula to investigate the presence of Osedax worms. Using an integrated morphological and molecular approach we report the existence of three new species to science: Osedax emmae sp. nov., Osedax martini sp. nov., and Osedax teoi sp. nov. We performed population genetics’ analyses to assess the genetic connectivity between populations of two of these species. To characterize the microbial communities associated with the three Iberian species, we produced new data using 16S rRNA amplicon sequencing, finding no species-specific communities among species. Nevertheless, we found four core microbes present not only across these three Iberian species but also in the Antarctic Osedax deceptionensis. Altogether, our findings substantially expand current knowledge of this group of marine invertebrates in Atlanto-Mediterranean deep-water habitats.