title: Microtexture of larval shell of oyster, Crassostrea nippona: a FIB-TEM study.
abstract: The initial formation and subsequent development of larval shells in marine bivalve, Crassostrea nippona were investigated using the FIB-TEM technique. Fourteen hours after fertilization (the trochophore stage), larvae form an incipient shell of 100-150nm thick with a columnar contrast. Selected-area electron diffraction analysis showed a single-crystal aragonite pattern with the c-axis perpendicular to the shell surface. Plan-view TEM analysis suggested that the shell contains high density of {110} twins, which are the origin of the columnar contrast in the cross-sectional images. 72h after fertilization (the veliger stage), the shell grows up to 1.2-1.4mum thick accompanying an additional granular layer between the preexisting layer and embryo to form a distinctive two-layer structure. The granular layer is also composed of aragonite crystals sharing their c-axes perpendicular to the shell surface, but the crystals are arranged with a flexible rotation around the c-axes and not restricted solely to the {110} twin relation. No evidence to suggest the existence of amorphous calcium carbonate (ACC) was found through the observation. The well-regulated crystallographic properties found in the present sample imply initial shell formation probably via a direct deposition of crystalline aragonite.
authors.affiliation: Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Kudo
authors.forename: Jun
authors.initials: J
authors.lastname: Kameda
authors.forename: Kazuko
authors.initials: K
authors.lastname: Saruwatari
authors.forename: Noriaki
authors.initials: N
authors.lastname: Ozaki
authors.forename: Keiju
authors.initials: K
authors.lastname: Okano
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Nagasawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kogure
mesh_terms: D000818:Animals; D002119:Calcium Carbonate / Q000737:chemistry; D049896:Crassostrea / Q000737:chemistry* / Q000648:ultrastructure*; D007814:Larva / Q000737:chemistry* / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission
chemical_list: D002119:Calcium Carbonate