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Class Eustigmatophyceae (“true eyespot”) was separated from the yellow-green Tribophyceae (Xanthophyceae) when the eyespot was found to lie outside the chloroplast (Hibberd and Leedale 1970, 1971, 1972). Other structural differences included their biflagellate condition although several have only a single emergent flagellum.

The eyespot is described as “a large conspicuous orange-red body in the extreme anterior end of the motile cell."

As of 2010 there are eight genera in the class, including Chlorobotrys, Ellipsoidion,
Eustigmatos, Monodopsis, Nannochloropsis, Pseudocharaciopsis, Pseudostaurastrum
and Vischeria (Ott and Oldham-Ott 2003).


Hibberd, D.J., and G.F. Leedale 1970. Eustigmatophyceae – a new algal class with unique organization of the motile cell. Nature 225:758-760.

Hibberd, D.J., and G.F. Leedale 1971. A new algal class – the Eustigmatophyceae. Taxon 20:523-525.

Hibberd, D.J., and G.F. Leedale 1972. Observations on the cytology and ultrastructure of the new algal class, Eustigmatophyceae. Annals of Botany 36:49-71.

Ott, D.W., and C.K. Oldham-Ott 2003. Eustigmatophyte, Raphidophyte, and Tribophyte Algae. In: Freshwater Algae of North America. Wehr, J.D., and R.G. Sheath, Eds. (pp. 423-469).