Stentor amethystinus

Stentor amethystinus is a single-celled eukaryote. It is often 1.0 mm long and is found in freshwater ponds and lakes. Algae live in symbiosis with Stentor amethystinus, providing food for the ciliate, which then protects the algae. Unlike many of its relatives, Stentor amethystinus is red-violet in color, due to the chemical amethystin. The chemical amethystin is structurally similar to the chemical stentorin, which belongs to Stentor coeruleus.