Eustigmatophyte

Eustigmatophytes are a small group (7 genera; ~12 species) of eukaryotic algae that includes marine, freshwater and soil-living species. All eustigmatophytes are unicellular, with coccoid cells and polysaccharide cell walls. Eustigmatophytes contain one or more yellow-green chloroplasts, which contain chlorophyll a and the accessory pigments violaxanthin and β-carotene. Eustigmatophyte zoids (gametes) possess a single or pair of flagella, originating from the apex of the cell. Unlike other heterokontophytes, eustigmatophyte zoids do not have typical photoreceptive organelles (or eyespot); instead, an orange-red eyespot outside of a chloroplast is located at the anterior end of the zoid.

In terms of ecology, eustigmatophytes occur as photosynthetic autotrophs across a range of systems. Most eustigmatophyte genera live in freshwater or in soil, although Nannochloropsis contains marine species of picophytoplankton (2 → 4 μm).