Ciliates within the <i>Mesodinium rubrum/Mesodinium major</i> species complex harbor chloroplasts and other cell organelles from specific cryptophyte species. <i>Mesodinium major</i> was recently described, and new studies indicate that blooms of <i>M. major</i> are just as common as blooms of <i>M. rubrum</i>. Despite this, the physiology of <i>M. major</i> has never been studied and compared to ...