Welcome to the prey’s-eye view of the three-spined stickleback. Mark Purnell, a research fellow at the University of Leicester in England, stained the fish to highlight the skeleton and examined surface textures on the teeth. Each tooth is about the width of a human hair, and its texture indicates what the fish ate.
Sticklebacks that feed on worms lurking in the sand have scratched teeth; those that eat plankton floating near the top of the lake have smooth teeth. Purnell’s work on both modern and fossil sticklebacks and the wear on their teeth suggests that where the fish ate affected the evolution of their body shape—a first for evolutionary biology, which has never before used fossils to trace the evolutionary effects of feeding. Presumably, as the fossil fish changed what and where they ate, they faced different predators and their spiny defenses adapted accordingly.