Amorphous, Hydrous, Ferric Phosphatic Dermal Granule in Molpadi (Holothuroidea): Physical and Chemical Characterization and Ecologic Implications of the Bioinorganic Fraction

Heinz A. Lowenstam, George R. Rossman
 Division of Geological and Planetary Sciences
California Institute of Technology
Pasadena, CA  91125


The bioinorganic fraction of the dermal granules of Molpadia intermedia from a wide variety of habitats has been studied by chemical analysis, electron microscopy, X-ray diffraction, thermal analysis, visible and infrared spectroscopy and magnetic susceptibility. It was found to have many similarities to polynuclear iron(III) proteins. Silica was found to be an integral component of the granules. The proportions of the major elements, P and Si, were found to vary with habitat as well as the minor elements, Ca and Mg, whereas the Fe content remained relatively constant. Models are proposed for the microstructure of the granules and the processes of their growth.


SEM image showing the layer build-up of a large granule frm Molpadia.

last updated: 26-Jul-2023