title: Calcium Dependence of Settlement and Nematocyst Discharge in Actinulae of the Hydroid Tubularia mesembryanthemum.
abstract: The influence of Ca2+ and Mg2+ ions on both atrichous isorhiza (AI) discharge and settlement of actinular larvae of the hydroid Tubularia mesembryanthemum was investigated. Mg2+-supplemented artificial seawater (ASW) completely inhibited both events at a concentration of 206 mM, whereas lowered Mg2+ concentrations enhanced them. Ca2+ ions in the bathing solution highly regulated AI discharge and settlement, and Mg2+ ions may down-regulate these events. The effect of inorganic Ca2+-channel blockers, including Gd3+ and La3+, was also examined. Larval settlement was inhibited by Co2+, Ni2+, Cd2+, La3+, and Gd3+, with half inhibitory concentrations (IC50) of 5800, 260, 53, 45, and 7 {mu}M, respectively; AI discharge was also inhibited by these ions, with IC50 values of 6600, 500, 78, 41, and 5 {mu}M, respectively. These results suggest possible involvement of stretch-activated Ca2+ channels in the signal transmission of both AI discharge and larval settlement.
authors.affiliation: Biofouling Project, ERATO, Research Development Corporation of Japan, c/o Yokohama R&D center, Niigata Engineering Co. Ltd., 27 Shin-isogo-cho, Isogo-ku, Yokohama, 235, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kawaii
authors.affiliation: Biofouling Project, ERATO, Research Development Corporation of Japan, c/o Yokohama R&D center, Niigata Engineering Co. Ltd., 27 Shin-isogo-cho, Isogo-ku, Yokohama, 235, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamashita
authors.affiliation: Biofouling Project, ERATO, Research Development Corporation of Japan, c/o Yokohama R&D center, Niigata Engineering Co. Ltd., 27 Shin-isogo-cho, Isogo-ku, Yokohama, 235, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakai
authors.affiliation: Biofouling Project, ERATO, Research Development Corporation of Japan, c/o Yokohama R&D center, Niigata Engineering Co. Ltd., 27 Shin-isogo-cho, Isogo-ku, Yokohama, 235, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Biofouling Project, ERATO, Research Development Corporation of Japan, c/o Yokohama R&D center, Niigata Engineering Co. Ltd., 27 Shin-isogo-cho, Isogo-ku, Yokohama, 235, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Fusetani