Some Effects of Temperature on the Symbiotic Association between Zoochlorellae (Chlorophyceae) and the Sea Anemone Anthopleura xanthogrammica

Symbiotic algae (Chlorophyceae), which form intracellular associations with the sea anemone Anthopleura xanthogrammica, are sensitive to a prolonged elevated temperature when maintained within the host. Maintenance of the plant-animal association at 20°C results in a loss of algal mitotic activity and a decline in the density of the algae within the host. These effects are reversible if the association is returned to a cooler temperature (13°C). Sea anemones maintained at 13°C and 20°C expel intact algae to their environment. The continued expulsion of algae and the loss of algal mitotic activity are apparently responsible for the decline in algal numbers within the host at 20°C. It is postulated that temperature may be a limiting factor in determining the distribution of zoochlorellae within the natural populations of the host.