title: Needle-like grains across growth lines in the coral skeleton of Porites lobata.
abstract: The skeletal texture and crystal morphology of the massive reef-building coral Porites lobata were observed from the nano- to micrometer scale using an analytical transmission electron microscope (ATEM). The skeletal texture consists of centers of calcification (COCs) and fiber area. Fiber areas contain bundles of needle-like aragonite crystals that are elongated along the crystallographic c-axis and are several hundred nanometers to one micrometer in width and several micrometers in length. The size distribution of aragonite crystals is relatively homogeneous in the fibers. Growth lines are observed sub-perpendicular to the direction of aragonite growth. These growth lines occur in 1-2 μm intervals and reflect a periodic contrast in the thickness of an ion-spattered sample and pass through the interior of some aragonite crystals. These observations suggest that the medium filled in the calcification space maintains a CaCO₃-supersaturated state during fiber growth and that a physical change occurs periodically during the aragonite crystals of the fiber area.
authors.affiliation: Department of Natural History of Science, Hokkaido University Graduate School of Science, Sapporo, Hokkaido 060-0810, Japan. motai_satoko@mail.sci.hokudai.ac.jp
authors.forename: Satoko
authors.initials: S
authors.lastname: Motai
authors.forename: Takaya
authors.initials: T
authors.lastname: Nagai
authors.forename: Kohki
authors.initials: K
authors.lastname: Sowa
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Naoya
authors.initials: N
authors.lastname: Sakamoto
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Yurimoto
authors.forename: Jun
authors.initials: J
authors.lastname: Kawano
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000033:anatomy & histology* / Q000254:growth & development; D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000737:chemistry*; D003461:Crystallography; D008855:Microscopy, Electron, Scanning
chemical_list: D002119:Calcium Carbonate