Is autosporulation a feature of Nannochloris?

Abstract

The green algal genus Nannochloris Naumann was originally described as having a simple binary division mechanism and lacking autosporulation and a parental cell wall. An initial observation of autosporulation in one isolate ascribed to this genus encouraged a broader investigation to determine whether or not autosporulation is restricted to only certain forms or is the reproductive mechanism used in the genus as a whole. Five cultures were examined; all had typically chlorophycean ultrastructure and both chlorophylls a and b. Nannochloris atomus differed from the other forms (two Nannochloris spp., Nannochloris bacillaris, and Nannochloris maculants) in having a pyrenoid and different wall structure and other ultrastructural features. However, reproduction in all five was by autosporulation with a thin, yet clearly defined, parental wall surrounding the two–four daughter cells in electron micrographs. These and related findings of other workers point to the need for a redefinition of the genus.