Observations on the morphology, reproduction, and fine structure of Chlamydomonas segnis from Delta Marsh, Manitoba

Abstract

Variations in the morphology of Chlamydomonas segnis have been investigated under various cultural conditions. In cultures maintained at 250 ft-c and 15 °C without aeration, this alga assumed the form of a Gloeocystis, whereas in aerated mass-culture grown at 25–30 °C and 1000 ft-c the motile stage showed close similarity to the genus Gloeomonas. Cells of C. segnis growing in synchronous culture under high light intensity (1000 ft-c) and supplied with 5% CO2 in air (v/v) reproduced asexually to form four zoospores, whereas cells provided with air produced only two zoospores. When zoospores developed in light their increase in cell volume was not accompanied by an increase in the length of their flagella. Homothallic anisogamous sexual reproduction could be demonstrated under conditions unfavourable for growth. Ultrathin sections of cells developed in light revealed a lobate, cup-shaped chromatophore. The mitochondria possessed irregular profiles with constrictions and were mainly located on the outer surface of the chloroplast. Intracytoplasmic, convoluted inclusions and interthylakoidal crystals have been observed. Microbody-like organelles, similar to those in plant leaf tissue, occurred in autotrophically grown C. segnis.