A comparative study on the electron microscopic enzymo-cytochemistry of Paramecium bursaria from light and dark cultures

Electron microscopic structure and enzymo-cytochemistry of light- and dark-cultured Paramecium bursaria was compared. In light-cultured Paramecium bursaria, the Chlorella symbionts grew normally and only a few of them were digested. In dark-cultured Paramecium bursaria, the number of food vacuoles containing symbionts increased significantly and the Chlorella symbionts in food vacuoles degenerated gradually and were finally digested by host cells. The activity of the enzymes acid phosphatase, adenosine triphosphatase, succinate dehydrogenase and glucose-6-phosphatase was studied in paramecia cultured in both light and dark conditions. The results showed that paramecia cultured under the two different conditions differed in their cytoplasmic structures and enzyme cytochemical reactions. The dark-cultured paramecia displayed stronger enzyme cytochemical reactivity. It is suggested that under dark-culture conditions, the gradual degeneration of Chlorella symbionts can stimulate their host to intensify its food uptake and the digestive activities of related organelles; whereas under the light-culture conditions, Chlorella symbionts can supply nutrition to their host and inhibit the functional activities of some organelles of their host.