Their color gave them away. Ecologist Diane Stoecker was looking at plankton in samples of ocean water from the dock in Woods Hole Harbor in Massachusetts some 40 years ago when she spotted something strange. Under the microscope, she recognized Laboea strobila, shaped like an ice-cream cone—“yellowish green and very beautiful,” she recalls—and the smaller, more spherical Strombidium species—also oddly greenish.
Stoecker knew that these single-celled critters, named ciliates for the hairlike cilia that they bear, got their energy by feeding on other, smaller organisms. So why were the ones she saw so green—a color that generally signifies photosynthesis? Was the pigment leftover food, ingested algae or just the algae’s chloroplasts?
After some groundbreaking experiments, Stoecker was one of the first scientists to describe how these types of plankton not only hunted their prey, but also sequestered the chloroplasts of their food sources and used...