The mineral component of the axis and holdfast of some gorgonacean octocorals (Coelenterata: Anthozoa), with special reference to the family Gorgoniidae

This is the first detailed investigation of the mineral component of axes and holdfasts of Gorgonacea, including 58 species belonging to 5 families and 21 genera of Holaxonia and 4 families and 13 genera of Calcaxonia. X-ray diffraction, electron probe, and scanning electron microscope analyses indicated that aragonite or Mg-calcite occurred in most axes and holdfasts of 6 families. In marked contrast, amorphous carbonate hydroxylapatite occurred solely in the family Gorgoniidae, which in some species also had Mg-calcite or aragonite in holdfasts. These skeletal minerals appear to be taxonomically controlled. The distinctive morphology of carbonate hydroxylapatite in Gorgoniidae is illustrated by scanning electron micrographs.