title: Long-term Cultivation of the Deep-Sea Clam Calyptogena okutanii: Changes in the Abundance of Chemoautotrophic Symbiont, Elemental Sulfur, and Mucus.
abstract: Survival of deep-sea Calyptogena clams depends on organic carbon produced by symbiotic, sulfur-oxidizing, autotrophic bacteria present in the epithelial cells of the gill. To understand the mechanism underlying this symbiosis, the development of a long-term cultivation system is essential. We cultivated specimens of Calyptogena okutanii in an artificial chemosynthetic aquarium with a hydrogen sulfide (H2S) supply system provided by the sulfate reduction of dog food buried in the sediment. We studied morphological and histochemical changes in the clams' gills by immunohistochemical and energy-dispersive X-ray analyses. The freshly collected clams contained a high amount of elemental sulfur in the gill epithelial cells, as well as densely packed symbiotic bacteria. Neither elemental sulfur nor symbiotic bacteria was detected in any other organs except the ovaries, where symbiotic bacteria, but not sulfur, was detected. The longest survival of an individual clam in this aquarium was 151 days. In the 3 clams dissected on Days 57 and 91 of the experiment, no elemental sulfur was detected in the gills. The symbiotic bacteria content had significantly decreased by Day 57, and was absent by Day 91. For comparison, we also studied the deep-sea mussel Bathymodiolus septemdierum, which harbors a phylogenetically close, sulfur-oxidizing, symbiotic bacterium with similar sulfur oxidation pathways. Sulfur particles were not detected, even in the gills of the freshly collected mussels. We discuss the importance of the proportion of available H2S and oxygen to the bivalves for elemental sulfur accumulation. Storage of nontoxic elemental sulfur, an energy source, seems to be an adaptive strategy of C. okutanii.
authors.affiliation: Marine Biodiversity Research Program, and.
authors.forename: Kazue
authors.initials: K
authors.lastname: Ohishi
authors.affiliation: Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan;
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Department of Technical Services, Marine Works Japan, Ltd., Oppama higashi-cho, Yokosuka, Kanagawa 237-0063, Japan;
authors.forename: Akihiro
authors.initials: A
authors.lastname: Tame
authors.affiliation: Department of Marine Biodiversity Research, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan;
authors.forename: Chiho
authors.initials: C
authors.lastname: Kusaka
authors.affiliation: Department of Marine Biodiversity Research, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan;
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nagai
authors.affiliation: Enoshima Aquarium, 2-19-1 Katasekaigan, Fujisawa, Kanagawa 251-0035, Japan;
authors.forename: Makoto
authors.initials: M
authors.lastname: Sugimura
authors.affiliation: Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan; and.
authors.forename: Koji
authors.initials: K
authors.lastname: Inoue
authors.affiliation: Department of Technical Services, Marine Works Japan, Ltd., Oppama higashi-cho, Yokosuka, Kanagawa 237-0063, Japan;
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Uematsu
authors.affiliation: Department of Marine Biodiversity Research, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan;
authors.forename: Takao
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Department of Marine Biodiversity Research, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan;
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Ikuta
authors.affiliation: Department of Marine Biodiversity Research, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan;
authors.forename: Takashi
authors.initials: T
authors.lastname: Toyofuku
authors.affiliation: Marine Biodiversity Research Program, and Research and Development Center for Marine Biosciences, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan tadashim@jamstec.go.jp.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Maruyama
mesh_terms: D000818:Animals; D005880:Gills / Q000737:chemistry / Q000382:microbiology; D009093:Mucus / Q000737:chemistry; D049879:Mytilidae / Q000382:microbiology* / Q000502:physiology*; D013455:Sulfur / Q000032:analysis / Q000378:metabolism*; D013559:Symbiosis
chemical_list: D013455:Sulfur