title: Discovery of new hydrothermal activity and chemosynthetic fauna on the Central Indian Ridge at 18°-20° S.
abstract: Indian Ocean hydrothermal vents are believed to represent a novel biogeographic province, and are host to many novel genera and families of animals, potentially indigenous to Indian Ocean hydrothermal systems. In particular, since its discovery in 2001, much attention has been paid to a so-called 'scaly-foot' gastropod because of its unique iron-sulfide-coated dermal sclerites and the chemosynthetic symbioses in its various tissues. Despite increasing interest in the faunal assemblages at Indian Ocean hydrothermal vents, only two hydrothermal vent fields have been investigated in the Indian Ocean. Here we report two newly discovered hydrothermal vent fields, the Dodo and Solitaire fields, which are located in the Central Indian Ridge (CIR) segments 16 and 15, respectively. Chemosynthetic faunal communities at the Dodo field are emaciated in size and composition. In contrast, at the Solitaire field, we observed faunal communities that potentially contained almost all genera found at CIR hydrothermal environments to date, and even identified previously unreported taxa. Moreover, a new morphotype of 'scaly-foot' gastropod has been found at the Solitaire field. The newly discovered 'scaly-foot' gastropod has similar morphological and anatomical features to the previously reported type that inhabits the Kairei field, and both types of 'scaly-foot' gastropods genetically belong to the same species according to analyses of their COI gene and nuclear SSU rRNA gene sequences. However, the new morphotype completely lacks an iron-sulfide coating on the sclerites, which had been believed to be a novel feature restricted to 'scaly-foot' gastropods. Our new findings at the two newly discovered hydrothermal vent sites provide important insights into the biodiversity and biogeography of vent-endemic ecosystems in the Indian Ocean.
authors.affiliation: Precambrian Ecosystem Laboratory (PEL), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan. kentaron@jamstec.go.jp
authors.forename: Kentaro
authors.initials: K
authors.lastname: Nakamura
authors.forename: Hiromi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Junichi
authors.initials: J
authors.lastname: Miyazaki
authors.forename: Ken
authors.initials: K
authors.lastname: Takai
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Kawagucci
authors.forename: Takuro
authors.initials: T
authors.lastname: Noguchi
authors.forename: Suguru
authors.initials: S
authors.lastname: Nemoto
authors.forename: Tomo-o
authors.initials: TO
authors.lastname: Watsuji
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsuzaki
authors.forename: Takazo
authors.initials: T
authors.lastname: Shibuya
authors.forename: Kei
authors.initials: K
authors.lastname: Okamura
authors.forename: Masashi
authors.initials: M
authors.lastname: Mochizuki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Orihashi
authors.forename: Tamaki
authors.initials: T
authors.lastname: Ura
authors.forename: Akira
authors.initials: A
authors.lastname: Asada
authors.forename: Daniel
authors.initials: D
authors.lastname: Marie
authors.forename: Meera
authors.initials: M
authors.lastname: Koonjul
authors.forename: Manvendra
authors.initials: M
authors.lastname: Singh
authors.forename: Girish
authors.initials: G
authors.lastname: Beedessee
authors.forename: Mitrasen
authors.initials: M
authors.lastname: Bhikajee
authors.forename: Kensaku
authors.initials: K
authors.lastname: Tamaki
mesh_terms: D000818:Animals; D044822:Biodiversity; D049628:Body Size; D020405:Dermis / Q000378:metabolism; D049851:Gastropoda / Q000033:anatomy & histology / Q000648:ultrastructure; D005843:Geography; D060086:Hydrothermal Vents; D019156:Indian Ocean; D007501:Iron / Q000378:metabolism; D008969:Molecular Sequence Data; D012212:Rheology; D013314:Stress, Mechanical; D013440:Sulfides / Q000378:metabolism
chemical_list: D013440:Sulfides; D007501:Iron