CYCLOMORPHOSIS IN SCENEDESMUS-SUBSPICATUS (CHLOROCOCCALES, CHLOROPHYTA) - STIMULATION OF COLONY DEVELOPMENT AT LOW-TEMPERATURE

The UTEX 2532 strain of Scenedesmus subspicatus R. Chodat was grown in batch culture at 10 degrees C and 22 degrees C. At 22 degrees C only unicells developed. At the lower incubation temperature there was stimulation of colony production, with up to 67% 4-celled or 8-celled colonies. Colonies developed during the early stationary phase of growth. With the expression of both cold-water and warm-water ecomorphs, this ordered sequence of phenotypic plasticity can be termed a cyclomorphosis. Development of the complete range of phenotypic plasticity in certain species, and thus accurate identification of a laboratory culture such as S. subspicatus used in the present study, can be achieved only by use of a broader range of standard conditions of growth. At present, identification of preserved field samples from one site at different seasons is even more difficult.