Thin fibres emitted by the marine diatom Skeletonema costatum (Grev.) Cleve

Extracellular thin fibres emitted by Skeletonema costatum were examined with light and electron microscopes. By observation with scanning electron microscope, it was found that the fibres come out from each of the openings located near the base of the strutted processes, but none of them originated from other parts of the frustules. Although S. costatum excretes these mucilaginous threads the same as many other species in the family Thalassiosiraceae, it has never been known what conditions accelerate the excretion of mucous substances from diatom cells.