アザミサンゴの種内変異型の研究 : ポリプ色彩パターン、刺胞形態、共骨密度

Many scleractinian corals exhibit intraspecific variation in color and colony morphology. Several color morphs of Galaxea fascicularis have been described in Okinawan populations. Colonies of G. fascicularis have also been divided into types based on the shape of tentacular microbasic p-mastigophore (MpM) nematocysts and the density of the coenosteum. To understand the relationships of color morphs and types based on various characters, we studied color pattern of polyps, shape of tentacular nematocysts, and density of the coenosteum of colonies of G. fascicularis collected at Sesoko Island, Zampa and Teniya, Okinawa. Colonies of G. fascicularis were divided into three morphotypes based on the shape of tentacular MpM nematocysts. In addition to two morphotypes S and H, which were previously reported to possess different types of MpMs, we found mixed-type colonies (morphotype M) whose tentacles possessed both types of nematocysts. Although the average size of skeletal vesicles of the coenosteum of morphotype S colonies was greater than that of morphotype H colonies, the size of skeletal vesicles varied largely among colonies belonging to the same morphotype and appeared to be affected by environmental factors. We could not find clear relationships between the color morphs and the morphotypes based on the shape of tentacular nematocysts in G. fascicularis.