Skeletal architecture and microstructure of the calcifying coral Fungia simplex

This study presents the characterization of the skeletal structure of the coral Fungia simplex, a hermatypic resident of the shallow zones of tropical reefs. In contrast to most cnidarians, this species has a unique multi-septal skeletal architecture. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed the skeletal microstructure to be made up of bundles of thin needles of prismatic crystals. X-ray diffraction (XRD) indicated that the crystals are composed of aragonite with a preferred orientation exposing the {221} planes parallel to the septal surface and tilted by 20° with respect to the growth (c-) direction.