Photosymbiotic animals encrusting corals: dispersal, reproduction, and current status of their distribution

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Diplosoma simile and Trididemnum cyclops are considered to be wide-spreading species based on the faunal surveys in the Ryukyus, Taiwan, Panama, and some oceanic islands in North Pacific (i.e., Minami Daito-jima, Bonin Islands, Hawai'i). Especially, D. simile has already spread in not only Indo-Pacific but also in Caribbean Panama. In the monthly monitoring of drifting seaweeds, colonies of T. cyclops were found on the Sargassum leaves, indicating that these species have a long-dispersal ability using drifting materials. These two species are the most possible candidates that expand the distribution range toward higher latitude following the increase of seawater temperature.Larval spawning was confirmed by direct observation and histological and electron-microscopic studies in a cyanobacteriosponge Terpios hoshinota that encrusts scleractinian corals.A new species of a colonial hydroid Zancrea sango was described. This species spread the colonies on a scleractinian coral colony.