PHYLUM EUSTIGMAOTA

I. SYNONYM: Eustigs.

II. PHYLUM CHARACTERISTICS:

A. Structure and Physiology

Cell Form: Organisms coccoid.

Flagella: Never found in vegetative forms. Two flagella; posterior whiplash and anterior tinsel with two rows of thick mastigonemes; often whiplash flagellum missing. Flagellar swelling at the base of the tinsel flagellum and associated with an eyespot.

Basal Bodies: Basal bodies perpendicular and with rhizoplast.

Cell Covering: Of one piece, composition unknown.

Chloroplasts: Numerous yellow-green chloroplasts with chlorophylls a, c₁, and c₂ (e?); also with B-carotene, and some xanthophylls which are not found in the xanthophytes; a large eyespot situated within the cytoplasm at the anterior end of the cell. Polyhedral pyreoid on inner surface of the chloroplast.

Food Reserves: A glucose polysaccharide (not yet characterized).

Mitochondria: Tubular cristae.

Golgi: Present.

Nucleus: Details not known, but associated with a rhizoplast.

Centrioles: Not reported.

Inclusions and Ejectile Organelles: Red eyespot.

B. Mitosis, Meiosis and Life History

Mitosis: Not described.

Meiosis: Not reported.

Sexual Reproduction and Life History: Not reported.

C. Ecology: Mainly found in fresh water but some in soil and marine plankton.

III. TAXONOMY OF THE EUSTIGMAOTA

A. Number: 12 species (7 genera).

B. Comparative Taxonomy:

Prior to the recognition by Hibberd and Leedale (1970) of the unique stucture of the eustig motile cell, members of the Eustigmatotista were placed in the xanthophytes. Now many sources (e.g. Bold and Wynne 1985; Sze 1986; and Lee 1980) consider the eustigs to be a class within the chrysophytes. Margulis and Schwartz (1988, Pr-10), Sleigh et al. (1984), and Hibberd (1990) consider the differences between the eustigs, xanthophytes and chrysophytes sufficient to place them into separate phyla. The phylogeny of Taylor (1976) shows the eustigs emerging from a line near the chloromonads and prior to the chrysophyte complex. The analysis of Dodge (1973) shows the eustigs occupying a link between the euglenoids and xanthophytes (or chrysophyte complex).  I follow the phylogeny of Sogin and Patterson (Tree of Life Project) in uniting these with other heterokont phyla.

C. Proposed Taxonomy of the Eugstigmaota:

CLASS EUSTIGMATOLOGIA

This class has a single order, EUSTIGMATINES.

examples: Eustigmatos, Vischeria, Chlorobotrys, Ellipsoidion, Pleurochloris, Polyedriella, Pseudocharaciopsis.