title: An aposymbiotic primary coral polyp counteracts acidification by active pH regulation.
abstract: Corals build their skeletons using extracellular calcifying fluid located in the tissue-skeleton interface. However, the mechanism by which corals control the transport of calcium and other ions from seawater and the mechanism of constant alkalization of calcifying fluid are largely unknown. To address these questions, we performed direct pH imaging at calcification sites (subcalicoblastic medium, SCM) to visualize active pH upregulation in live aposymbiotic primary coral polyps treated with HCl-acidified seawater. Active alkalization was observed in all individuals using vital staining method while the movement of HPTS and Alexa Fluor to SCM suggests that certain ions such as H+could diffuse via a paracellular pathway to SCM. Among them, we discovered acid-induced oscillations in the pH of SCM (pHSCM), observed in 24% of polyps examined. In addition, we discovered acid-induced pH up-regulation waves in 21% of polyps examined, which propagated among SCMs after exposure to acidified seawater. Our results showed that corals can regulate pHSCMmore dynamically than was previously believed. These observations will have important implications for determining how corals regulate pHSCMduring calcification. We propose that corals can sense ambient seawater pH via their innate pH-sensitive systems and regulate pHSCMusing several unknown pH-regulating ion transporters that coordinate with multicellular signaling occurring in coral tissue.
authors.affiliation: Marine and Environmental Sciences Course, Graduate School of Engineering and Science, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ohno
authors.affiliation: Department of Bioresources Engineering, National Institute of Technology, Okinawa College, 905 Henoko, Nago, Okinawa 905-2192, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Iguchi
authors.affiliation: Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan.
authors.forename: Chuya
authors.initials: C
authors.lastname: Shinzato
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan.
authors.forename: Mayuri
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Suzuki
authors.affiliation: Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, 3422 Sesoko, Motobu, Okinawa 905-0227, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Sakai
authors.affiliation: Marine and Environmental Sciences Course, Graduate School of Engineering and Science, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan.|Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, 3422 Sesoko, Motobu, Okinawa 905-0227, Japan.|Japan Science and Technology Agency (JST)/Japan International Cooperation Agency (JICA) SATREPS, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D000143:Acids / Q000378:metabolism*; D000818:Animals; D037421:Anthozoa / Q000502:physiology*; D005898:Glass; D006863:Hydrogen-Ion Concentration; D021621:Imaging, Three-Dimensional; D010012:Osteogenesis; D011721:Pyrenes / Q000378:metabolism; D012623:Seawater; D013451:Sulfonic Acids / Q000378:metabolism; D013559:Symbiosis; D015854:Up-Regulation
chemical_list: C538892:8-hydroxy-1,3,6-pyrenetrisulfonic acid; D000143:Acids; D011721:Pyrenes; D013451:Sulfonic Acids