title: Biomineralization in living hypercalcified demosponges: toward a shared mechanism?
abstract: Massive skeletons of living hypercalcified sponges, representative organisms of basal Metazoa, are uncommon models to improve our knowledge on biomineralization mechanisms and their possible evolution through time. Eight living species belonging to various orders of Demospongiae were selected for a comparative mineralogical characterization of their aragonitic or calcitic massive basal skeleton. The latter was prepared for scanning and transmission electron microscopy (SEM and TEM), selected-area electron diffraction (SAED) and X-ray diffraction (XRD) analyses. SEM results indicated distinctive macro- and micro-structural organizations of the skeleton for each species, likely resulting from a genetically dictated variation in the control exerted on their formation. However, most skeletons investigated shared submicron to nano-scale morphological and crystallographical patterns: (1) single-crystal fibers and bundles were composed of 20 to 100nm large submicronic grains, the smallest structural units, (2) nano-scale likely organic material occurred both within and between these structural units, (3) {110} micro-twin planes were observed along aragonitic fibers, and (4) individual fibers or small bundles protruded from the external growing surface of skeletons. This comparative mineralogical study of phylogenetically distant species brings further evidence to recent biomineralization models already proposed for sponges, corals, mollusks, brachiopods and echinoderms and to the hypothesis of the universal and ancestral character of such mechanisms in Metazoa.
authors.affiliation: Department of Invertebrates, Royal Belgian Institute of Natural Sciences, B-1000 Brussels, Belgium; Laboratoire de Biologie marine, Université Libre de Bruxelles, B-1050 Brussels, Belgium. Electronic address: melany.gilis@epfl.ch.
authors.forename: Melany
authors.initials: M
authors.lastname: Gilis
authors.affiliation: Aix-Marseille Université and Centre Interdisciplinaire de Nanosciences de Marseille (CINaM), Campus de Luminy, F-13288 Marseille, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Grauby
authors.affiliation: Department of Invertebrates, Royal Belgian Institute of Natural Sciences, B-1000 Brussels, Belgium; Laboratoire de Biologie marine, Université Libre de Bruxelles, B-1050 Brussels, Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: Willenz
authors.affiliation: Laboratoire de Biologie marine, Université Libre de Bruxelles, B-1050 Brussels, Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: Dubois
authors.affiliation: Aix-Marseille Université and Centre Interdisciplinaire de Nanosciences de Marseille (CINaM), Campus de Luminy, F-13288 Marseille, France.
authors.forename: Vasile
authors.initials: V
authors.lastname: Heresanu
authors.affiliation: Aix-Marseille Université and Centre Interdisciplinaire de Nanosciences de Marseille (CINaM), Campus de Luminy, F-13288 Marseille, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Baronnet
mesh_terms: D060105:Animal Shells / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D011161:Porifera / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D002119:Calcium Carbonate
keywords: Biomineral; Calcification; Calcium carbonate; Demospongiae; Hypercalcified sponges; Porifera