1. Spherical cells 7–11 mm in diameter, conspicuous (2 mm thick) clear extracellular matrix, greyish red to reddish brown, exhibiting positive phototaxis.
2. The single chloroplast has numerous lobes extending from multiple pyrenoids located throughout the cell.
3. Pyrenoids, containing tubular thylakoids, are exposed to the cytoplasm and are usually surrounded by a starch sheath.
4. Starch grains also present elsewhere in cells, usually adjacent to chloroplast lobes.
5. Peripheral thylakoids absent.
6. Golgi bodies always closely associated with a mitochondrion and usually located at the cell periphery.
7. Nucleus peripheral with a single nucleolus appressed to the region of the nuclear envelope usually closest to the cell center.
8. Low molecular weight carbohydrates are floridoside, digeneaside and trehalose.
From Patrick J. Keeling ,at Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada and Canadian Institute for Advanced Research, Integrated Microbial Biodiversity program, Canada.
Keeling PJ, Burki F, Wilcox HM, Allam B, Allen EE, Amaral-Zettler LA, et al. (2014) The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): Illuminating the Functional Diversity of Eukaryotic Life in the Oceans through Transcriptome Sequencing. PLoS Biol 12 (6): e1001889.