This project investigated the marine ciliate, Mesodinium rubrum, in order to understand how it steals, utilizes, and regulates organelles from cryptophyte algae. Mesodinium rubrum acquires most of its energy from stolen chloroplasts, despite lacking genes necessary to control these foreign organelles. Instead, the ciliate also steals and utilizes the nucleus from its prey, thereby acquiring its entire metabolism and biochemical potential. The ciliate is unique in its ability to fully exploit foreign organelles, and this project sought to better understand how it is capable of doing so. The information gained from this project helped to further our understanding of the ecology and biology of this important marine ciliate. It also shed light on the dynamics of organelle acquisition and exploitation in an organism that appears to be in process of permanently acquiring a plastid. This project helped to establish M. rubrum as a model species for understanding organelle sequestration and acquisitions.