The chitinous nature of filaments ejected by Phaeocystis (Prymnesiophyceae)

Filaments ejected by Phaeocystis globosa Scherffel, organized in star-like structures, were observed and analyzed before and after their discharge from cells. Ultrastructural observations obtained after cryofixation and cryosubstitution led to a model for their storage within the cell and for their ejection from the cell. Electron diffraction analysis on the ejected filaments demonstrated their chitinous composition. This technique indicated without ambiguity that each filament was in fact a whisker-like cr-chitin crystal, with the axes of the corresponding polymer chains aligned with the filament's axis. X-ray microanalysis of the mats of filaments indicated that the silica content suggested by earlier workers was an artifact resulting from the filtration procedure.