MIXOTROPHY IN MARINE SPECIES OF CHRYSOCHROMULINA (PRYMNESIOPHYCEAE) - INGESTION AND DIGESTION OF A SMALL GREEN FLAGELLATE

Species of Chrysochromulina (Prymnesiophyceae) were screened for their ability to ingest inert material and live cells of a small green flagellate. The species C. brevifilum showed a marked preference for the small green flagellate over carmine particles and the rate of ingestion of the flagellate was proportional to its concentration and inversely proportional to light intensity. Ingestion was also higher by phosphate-starved Chrysochromulina, and a clear predator/prey relationship was demonstrated with C. brevifilum clearly benefiting, in terms of growth rate, from the ingestion of the small green flagellate. Electron micrographs confirmed that digestion occurs. Mixotrophy in Chrysochromulina appears to be a complex mode of nutrition, dependent on environmental parameters and on nutritional status. Some species take up dissolved organic carbon as well as particulate prey and other species are pure autotrophs. As yet there does not appear to be a pattern to phagotrophic behaviour in Chrysochromulina that would allow general conclusions to be drawn on the factors controlling modes of nutrition.