title: Crystallographic orientation and concentric layers in spicules of calcareous sponges.
abstract: In this work, the crystallography of calcareous sponges (Porifera) spicules and the organization pattern of the concentric layers present in their inner structure were investigated in 10 species of the subclass Calcaronea and three species of the subclass Calcinea. Polished spicules had specific concentric patterns that varied depending on the plane in which the spicules were sectioned. A 3D model of the concentric layers was created to interpret these patterns and the biomineralization process of the triactine spicules. The morphology of the spicules was compared with the crystallographic orientation of the calcite crystals by analyzing the Kikuchi diffraction patterns using a scanning electron microscope. Triactine spicules from the subclass Calcinea had actines (rays) elongated in the 〈210〉 direction, which is perpendicular to the c-axis. The scale spicules of the hypercalcified species Murrayona phanolepis presented the c-axis perpendicular to the plane of the scale, which is in accordance with the crystallography of all other Calcinea. The triactine spicules of the calcaronean species had approximately the same crystallographic orientation with the unpaired actine elongated in the ∼[211] direction. Only one Calcaronea species, whose triactine was regular, had a different orientation. Three different crystallographic orientations were found in diactines. Spicules with different morphologies, dimensions and positions in the sponge body had similar crystallographic directions suggesting that the crystallographic orientation of spicules in calcareous sponges is conserved through evolution.
authors.affiliation: Centro Brasileiro de Pesquisas Físicas, Xavier Sigaud, 150, 22290-180 Rio de Janeiro, Brazil. Electronic address: alinhares@cbpf.br.
authors.forename: André Linhares
authors.initials: AL
authors.lastname: Rossi
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Biologia, Laboratório de Biologia de Porifera, 21941-590 Rio de Janeiro, Brazil.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Ribeiro
authors.affiliation: Centro Brasileiro de Pesquisas Físicas, Xavier Sigaud, 150, 22290-180 Rio de Janeiro, Brazil.
authors.forename: Moara
authors.initials: M
authors.lastname: Lemos
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Ciências Biomédicas, Laboratório de Biomineralização, 21941-590 Rio de Janeiro, Brazil.
authors.forename: Jacques
authors.initials: J
authors.lastname: Werckmann
authors.affiliation: Centro de Medicina Regenerativa, Faculdade de Medicina de Petrópolis, Av Barão do Rio Branco, 25680-120 Petrópolis, RJ, Brazil.
authors.forename: Radovan
authors.initials: R
authors.lastname: Borojevic
authors.affiliation: Western Australian Museum, Department of Aquatic Zoology, Locked Bag 49, Welshpool DC, WA 6986, Australia.
authors.forename: Jane
authors.initials: J
authors.lastname: Fromont
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Biologia, Laboratório de Biologia de Porifera, 21941-590 Rio de Janeiro, Brazil.
authors.forename: Michelle
authors.initials: M
authors.lastname: Klautau
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Ciências Biomédicas, Laboratório de Biomineralização, 21941-590 Rio de Janeiro, Brazil.
authors.forename: Marcos
authors.initials: M
authors.lastname: Farina
mesh_terms: D000818:Animals; D002113:Calcification, Physiologic; D003461:Crystallography; D019143:Evolution, Molecular; D005109:Extracellular Matrix / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010802:Phylogeny; D011161:Porifera / Q000033:anatomy & histology*
keywords: Biomineralization; Calcarea; Calcaronea; Calcinea; Porifera; Spicule crystallography