Polysaccharide localization, coccolith formation, and Golgi dynamics in the coccolithophorid Hymenomonas carterae

Abstract

The periodic acid-thiocarbohydrazide-silver proteinate staining technique according to Thiéry (1967) was employed for visualization of the ultrastructural localization of polysaccharides in the coccolithophorid alga Hymenomonas carterae . Preferential staining was observed in the Golgi apparatus, including constituents and precursors of "scales" and " coccoliths " (scales with a rim of elaborate CaCO3 crystals), which are extruded and become part of the cell wall. Cells fixed in the presence of the polyanion-precipitating agent cetylpyridiniumchloride showed a voluminous coat over the crystalline matter of the coccolith giving the extracellular coccoliths the appearance of being glued together. Soluble acid polysaccharides are thought to occur in the coat. Evidence is presented that the coat and the crystalline matter are produced simultaneously. The excellent stainability of the Golgi apparatus allowed study of its morphology in considerable detail, and permitted a tentative reconstruction of the formation of coccoliths and scales and of the Golgi dynamics in general. The question of whether Golgi cisternae are mobile or static entities is dealt with.