[M-IS28] Fluid-sediment migration and geo-bio interaction

[MIS28-P03] Taxonomy and diet of the Ophryotrocha (Annelida: Dorvilleidae) from whale- falls in the Tsukumo Bay, Japan

*Midori Suzuki¹, Robert Gwyn Jenkins¹, Shouzo Ogiso², Nobuo Suzuki³ (1.Division of Environmental Science and Engineering, Graduate School of Natural Science and Technology, Kanazawa University, 2.Kanazawa university, 3.Institute of Nature and Environmental Technology, Kanazawa university)

Keywords:whale-falls, Dorvilleidae, Chemosynthesis

Decomposition of large organic-falls, e. g. sunken whale carcasses is a part of nutrient cycle (Smith et al., 2015). The decomposition is performed by not only microbes but also some animals, e. g. the polychaetes. Some polychaetes can be found from inside of decaying bone, however, roles of the polychaetes animals are poorly understood. We examined the organic carbon isotope ratio and DNA(COI) of polychaete Ophryotrocha (Annelida: Dorvilleidae), a species lived in the whale bone deployed in the Tsukumo Bay. They are exposed to stress in the form of high levels of hydrogen sulfide but have successfully invaded into the bone. Morphological observation revealed the species is mainly characterized by shape of jaw and we considered as new species. Phylogenetic analyses based on COI suggest that they have independently invaded into whale falls, hydrothermal vent and methane seep from normal environment for each taxon group. The examined Ophryotrocha sp. had the broadest δ¹³C range (-33.8‰~-19.0‰) among other species lived on/in the bones. It indicates that some of them fed on bacterial mat such as Beggiatoa sp. (-37.2‰~-28.5‰) but some of them don’t. These results highlight the role of Ophryotrocha has diverse food source, and it would be an advantage to adapt various “extreme environment” such as vent, seep, and whale falls.