CHLAMYDOMONAS

genus of green biflagellated single-celled organisms of disputed classification, placed botanically in the green algal order, Volvocales, and zoologically in the plantlike protozoan order, Volvocida. Chlamydomonas is considered a primitive life form of evolutionary significance. The cell has a spherical cellulose membrane (theca), a stigma (eye-spot), and a cup-shaped, pigment-containing chloroplast. Although photosynthesis occurs, nutrients also may be absorbed through the cell surface. Asexual reproduction is by zoospores; sexual reproduction is by formation of gametes. The development of motility, sexuality, and fusion seems dependent on the production of substances (termones, gamones) that have a regulatory action similar to hormones. Chlamydomonas is found in soil, ponds, and ditches polluted by manure. It may colour water green. The species C. nivalis, which contains the red pigment hematochrome, imparts a red colour to melting snow.