Observations on Bristle- and Scale-Production in Mallomonas caudata (Chrysophyceae)

Mallomonas plumosa(Chrysophyceae), a new species from Australia

“…At the proximal end the shaft is flattened and obliquely angled to form the attachment to the scale. The transformation of this flattened attachment into the hollow shaft of the plume strongly suggests that the whole plume is formed by the rolling-up of a flat structure, as reported for the bristles of M. caudata (Wujek & Kristiansen, 1978). It seems likely that the plume-bristles are homologous with the bristles of the body scales.…”

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.…”

“…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 seems to have been disproved by Mignot & Brugerolle (1982) who demonstrated that the vesicle membrane has a positive reaction when treated with the PATAg technique of Thiery & Rambourg (1974), while the chloroplast ER shows a negative reaction.…”

“…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. Extrusion of scales into the colonial investment is a much more irregular process in…”

“…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).…”