Ultrastructure and assembly of the scale case inSynura(Synurophyceae Andersen)

Scale formation inTessellaria volvocina(Synurophyceae)

“…Silica scale formation has been documented for Synura and Mallomonas (Belcher, 1969;Schnepf & Deichgr/iber, 1969;Wujek & Kristiansen, 1978;McGrory & Leadbeater, 1981;Leadbeater, 1986Leadbeater, , 1990Beech, Wetherbee & Pickett-Heaps, 1990) and follows the same basic steps in the two genera, any differences being concerned with the ornamentation of the scale and the additional production of bristles in Mallomonas. Schnepf & Deichgr/iber (1969) believed that the silica deposition vesicle is produced by fusion of small vesicles from the Golgi apparatus but Wujek & Kristiansen (1978) claimed that the SDV is also partly formed by material budding off from the chloroplast ER.…”

“…This mechanism has been suggested for Synura (Schnepf & Deichgrfiber, 1969;Brugerolle & Bricheux, 1984) and Mallomonas (Wujek, 1978). Leadbeater (1986Leadbeater ( , 1990 stated that the scales of Synura join the scale-case by insertion into a predetermined intercalary position. Wujek & Kristiansen (1978) reported that scales of Mallomonas may be released anywhere on the cell surface but the final imbrication of the scales is still precise.…”

“…Mignot & Brugerolle (1982) Leadbeater (1981) pointed out that in all chrysophycean and synurophycean species so far studied, silica is always laid down within a silica deposition vesicle closely associated with a cisterna of ER, be it chloroplast ER or cytoplasmic ER. Leadbeater (1986) described how developing scales at various stages of maturity are found close together in a cell. His Fig.…”

“…1; see Pipes, Leedale & Tyler, 1991). Leadbeater (1990) discussed how a row of scales, maturing along the length of the righthand chloroplast from the anterior to posterior, is inserted into the scale case of Synura. Since the chloroplast of Tessellaria does not run the length of the cell, a gradient of scales maturing in this way is not possible.…”

“…Scale formation involving silica deposition has been documented in detail for members of the Chrysophyceae [Paraphysomonas de Saedeleer (Manton & Leedale, 1961;Lee, 1978;Hibberd, 1979;McGrory & Leadbeater, 1981;Preisig & Hibberd, 1983), Spiniferomonas Takahashi, Polylepidomonas Preisig et Hibberd and Chrysosphaerella Lauterborn (Preisig & Hibberd, 1983)] and the Synurophyceae [Synura Ehrenberg (Schnepf & Deichgrfiber, 1969;McGrory & Leadbeater, 1981;Mignot & Brugerolle, 1982;Brugerolle & Bricheux, 1984;Leadbeater, 1986Leadbeater, , 1990 and Mallomonas Perty (Belcher, 1969;Wujek & Kristiansen, 1978;McGrory & Leadbeater, 1981;Mignot & Brugerolle, 1982)] and is one of the characters used by Andersen (1987) in the separation of the Synurophyceae from the Chrysophyceae sensu lato. Tessellaria volvocina Playfair, tentatively placed within the Synurophyceae on the basis of certain ultrastructural features (Pipes, Leedale & Tyler, 1991), has an unusual arrangement and distribution of its siliceous scales (Tyler et al, 1989).…”