The optical brightener Calcofluor White disorders thecal architecture and inhibits cell division of Cryothecomonas longipes Schnepf et Kuhn, a marinenanoflagellate incertae sedis

Calcofluor White inhibits the division of the marine nanoflagellate Cryothe comonas longipes and causes the development of monstrously lobed cells. It disturbs the assembly of a putative noncellulosic fibrillar polysaccharide in the theca. The compact layer of the theca becomes thicker and wider, les s densely packed and less rigid. The deposition of thecal components become s uncoordinated. In consequence the initially unaffected coat of the theca and loose portions of the compact layer protrude from the cell surface. The se are then convoluted, with the coat on their convex faces. The spacing of the coat ridges is increased here. The tension between the different layer s obviously stabilizes the theca and contributes to its rigidity and elasti city.