The use of fluorochromes in the cytochemical characterization of some phytoflagellates

Summary Sixteen fluorochromes were tested for the cytochemical characterization of two dinoflagellates (Amphidinuim carterae, Prorocentrum micans) and one chlorophycean flagellate (Dunaliella tertiolecta). Depending on the fluorochrome used, various cellular components (incuding the plasma membrane, thecal plates, pusule, trichocysts, nucleus, lipid bodies and vacuoles) were revealed. The different colours obtained from single or double fluorochrome staining enabled the differentiation and identification of most cellular components. Protoplasmic staining with Fluorescein diacetate suggested the occurrence of esterases in the three phytoflagellates. Rhodamine B, Neutral Red, FluoroBora P and Nile Blue revealed extensive occurrence of lipoid bodies inA. carterae, but Nile Blue showed considerable difference from the other stains in the inclusion size and intracellular location of these bodies. Chlortetracycline binding, and its inhibition by the Ca²⁺ionophore A23187, indicated that the plasma membrane, pusule system and trichocysts contain sites of Ca²⁺ binding. Calcofluor White ST proved superior to Congo Red and Lucifer Yellow in elucidating structural details of the thecal plates ofP. micans. While Acridine Orange revealed the presence of surface-coat acidic polysaccharides, the fluoresceinated lectins established their glycoconjugate nature in all the three flagellates. Possible mechanisms of fluorochrome uptake are discussed.