title: Internal skeletal analysis of the colonial azooxanthellate scleractinian Dendrophyllia cribrosa using microfocus X-ray CT images: underlying basis for its rigid and highly adaptive colony structure.
abstract: Dendrophyllid Scleractinia exhibit a variety of colonial morphologies, formed under the strict constraints on (1) budding sites, (2) orientations of the directive septa of offsets, (3) inclination of budding direction, and (4) those constraints in every generation. Dendrophyllia cribrosa exhibits a sympodial dendroid form, characteristically large coralla, and occasional fusions of adjacent branches within the same colony. Adjacent corallites are bound and supported by coenosteum skeleton. This study examined the inner skeletal structures at the junctions of fused branches using a non-destructive microfocus X-ray computed tomography (CT) imaging approach, and considered the reasons for the large colonial sizes and their adaptive significance. Three-dimensional reconstructions of two-dimensional X-ray CT images reveal that individual corallites are not directly connected in fused parts. Additionally, no completely buried individuals were found within fused skeleton. When adjacent branches approach one another, constituent corallites change their growth directions to avoid collisions between the branches. The adjacent branches fuse without a reduction in the number of constituent corallites, leading to the establishment of reticular and rigid colonial structures. In addition, a nearly even distribution of individuals on the colony surface facilitates efficient intake of nutrients. Thus, the growth of large D. cribrosa colonies involves avoidance of collision between constituent individuals, the reinforcement of colonial structure, and efficient uptake of nutrients. These observations provide insights on the dynamics of interrelationships between colony-making mechanisms and the adaptive strategies required under habitat conditions such as specific current activities.
authors.affiliation: Seto Marine Biological Laboratory, Field Science Education and Research Center, Kyoto University, 459 Shirahama, Nishimuro, Wakayama 649-2211, Japan. Electronic address: a.sentoku@gmail.com.
authors.forename: Asuka
authors.initials: A
authors.lastname: Sentoku
authors.affiliation: Department of Geosciences, Faculty of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. Electronic address: 1027kb@gmail.com.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Morisaki
authors.affiliation: Department of Geosciences, Faculty of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. Electronic address: masumoto@sci.osaka-cu.ac.jp.
authors.forename: Shinji
authors.initials: S
authors.lastname: Masumoto
authors.affiliation: Department of Geosciences, Faculty of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. Electronic address: ohno.archen@gmail.com.
authors.forename: Rie
authors.initials: R
authors.lastname: Ohno
authors.affiliation: Kochi Insutitute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi Core Center, 200 Monobe-otsu, Nankoku, Kochi 783-8502, Japan. Electronic address: tomi@jamstec.go.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Tomiyama
authors.affiliation: Department of Geosciences, Faculty of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. Electronic address: ezaki@sci.osaka-cu.ac.jp.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ezaki
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000033:anatomy & histology* / Q000254:growth & development*; D021621:Imaging, Three-Dimensional; D007564:Japan; D014057:Tomography, X-Ray Computed
keywords: Adaptive structure; Colony construction; Coral; Growth form; X-ray CT analysis