Structure and development of the scale case ofMallomonas adamas (Synurophyceae)

Summary The structure and development of the elaborate scale case ofMallomonas adamas (Synurophyceae) was studied throughout the cell cycle. Immediately following division, scale cases normally possess 30 siliceous scales, or 5 rows of 6 scales each. Scale rows overlap one another and spiral around the cell in a clockwise direction when viewed from either end of the cell. Throughout interphase, a duplicate set of 30 scales is manufactured and secreted into the existing scale case in a precise sequence, resulting in a scale case with 60 scales, or 5 rows of 12 scales each. Scales are not added to the scale case in rows, but individually positioned within the cytoplasm and inserted one at a time over the entire surface of the cell. Scales appear to occupy specific positions in the scale case. Scale cases are dynamic cell coverings, their elaborate patterning being maintained throughout cell growth and during division when half the parental scales are inherited by each daughter cell.