INFLUENCE OF TEMPERATURE AND LIGHT ON PARTICLE INGESTION BY THE FRESH-WATER PHYTOFLAGELLATE DINOBRYON

Particle uptake by two strains of the freshwater phytoflagellate Dinob ryon was studied using cells grown in clonal batch cultures and presen ted with fluorescent microspheres. Clearance rates were found to be st rongly dependent on temperature, with maximum clearance rate observed at around 20-degrees-C. Clearance rate over the diurnal light dark cyc le was observed to be slightly higher during the dark phase. Cultures quickly died when placed in total darkness. Cells of one strain grown for two weeks under dim irradiance (18 muE m-2s-1) showed reduced clea rance rates. For the other strain no relation was observed between cle arance rate and irradiance. It is concluded that photosynthesis is the primary mode of carbon acquisition for Dinobryon and that phagotrophy probably represents an adaptation for obtaining some other essential resource.