Aj. Gooday et al., APATITE PARTICLES IN THE TEST WALL OF THE LARGE AGGLUTINATED FORAMINIFER BATHYSIPHON MAJOR (PROTISTA), Journal of the Marine Biological Association of the United Kingdom, 75(2), 1995, pp. 469-481
In the North Atlantic, the tubular agglutinated foraminifer Bathysipho
n major occurs at bathyal depths off the coasts of North Carolina and
north-west Africa. Apart from its large size (up to almost 10 cm long)
, the most distinctive feature of this species is the appearance of th
e test wall which has a sooty black outer layer, about 20 mu m thick,
overlying a much thicker layer, pure white in colour and consisting of
sponge spicules and small quartz grains. The black layer is composed
of irregularly shaped, plate-like particles, 1-25 mu m in size. The na
ture and composition of these particles has been studied using light a
nd electron microscopy, x-ray microanalysis, electron diffraction anal
ysis and infrared spectroscopy. The particles contain calcium and phos
phorous and have electron diffraction patterns and infrared spectra co
nsistent with a hydroxyapatite composition. Minor amounts of iron are
probably responsible for their black colour. We believe that this repr
esents the first report of apatite-like (phosphorite) particles occurr
ing in the test of an agglutinated foraminifer. The particles are most
likely to originate as phosphorite grains which are agglutinated by t
he foraminifer, although the possibility of authigenic precipitation c
annot be eliminated. The function of the outer black layer is unknown.