Variation in silica scale morphology in Mallomonas pseudocoronata (Chrysophyceae)

Abstract

It was previously thought that a form of Mallomonas pseudocoronata with scales lacking the reticulate shield pattern might be considered a separate subspecies. Until now, however, the unreticulated form has been so rare in collections that a conclusive decision on its taxonomic status has not been possible. An abundance of cells with the unreticulated scale form, as well as more typical forms, have been found recently in Ontario phytoplankton collections. All other features of cell and scale morphology of the unreticulated forms (bristle structure, cell and scale size and shape) are identical to those of the heavily reticulated forms. It was concluded that a wide range of scale reticulation (from complete absence to heavily silicified reticulations) characterizes this species and that only one genotype is responsible for the range in scale morphology now known for M. pseudocoronata.