Photobiological Aspects of the Mutualistic Association Between Paramecium bursaria and Chlorella

Abstract

The main benefit involved in the mutualistic relationship between Paramecium bursaria and Chlorella has been traditionally interpreted as an adaptation to the struggle against starvation and nutrient limitation. However, other benefits such as the minimization of mortality and protection against damage by sunlight have been proposed recently. Here, we explore the photobiological adaptations and responses of P. bursaria and its algal symbionts when exposed to photosynthetically active and ultraviolet radiation, as well as the role of (photo-) oxidative and antioxidative defenses in the symbiosis. We conclude that the benefits are multiple and should be considered as a whole when assessing the selective advantage of living in mutualistic symbiosis.