Polytoma is a genus of colorless, free-living chlorophytes similar in form to
Chlamydomonas but lacking chlorophyll. Two flagella emanate from the anterior papilla of the cell, and cells have two contractile vacuoles at the flagellar base. The cell body can be spherical, ellipsoid, ovoid, or kidney-shaped.
Polytoma possesses a
leukoplast in place of a
chloroplast, in which many starch grains are concentrated; there are typically no
pyrenoids. Since they lack photosynthetic capability,
Polytoma species are entirely saprotrophic, obtaining nutrients from decaying organic matter. Some species possess an eyespot apparatus (stigma) in the anterior portion of the leucoplast, but in others this organelle is absent. Asexual reproduction occurs when the parent cell divides into four
zoospores, while in the parent cell wall. Sexual reproduction can be isogamous, anisogamous, or oogamous. ==Phylogeny==