Two-Round Ca2+ transient in papillae by mechanical stimulation induces metamorphosis in the ascidian, Ciona intestinalis type A

Marine invertebrate larvae are known to begin metamorphosis in response to environmentally-derived cues. However, little is known about the relationships between the perception of such cues and internal signalling for metamorphosis. To elucidate the mechanism underlying the initiation of metamorphosis in the ascidian, Ciona intestinalis type A (Ciona robusta), we artificially induced ascidian metamorphosis and investigated Ca2+ dynamics from pre- to post-metamorphosis. Ca2+ transients were observed and consisted of two temporally distinct phases with different durations before tail regression which is the early event of metamorphosis. In the first phase, Phase I, the Ca2+ transient in the papillae (adhesive organ of anterior trunk) was coupled with the Ca2+ transient in dorsally localised cells and endoderm cells just after mechanical stimulation. The Ca2+ transients in Phase I were also observed when applying only short stimulation. In the second phase, Phase II, the Ca2+ transient in ...