National Geographic
National Geographic: Blog: Tiny Critter Has Seven Sexes
Meet the freshwater Tetrahymena, a single-celled creature that has seven possible sexes. This article presents information from recent research that helps explain how the creature reproduces and how its sex is determined.
University of California
Tetrahymena as a Unicellular Model Organism
Information on Tetrahymena thermophila and why it is an important unicellular organism.