As larger predators began appearing, the schooling beakworm soon began to appear on the menu. As a response they became smaller in size, but greater in number. A swarm can contain as many as 150 worms (each about the size of a sardine). They move restlessly around in the open water looking for medium-sized or small prey, which they tear apart with their razor-sharp beaks. Large predators are avoided by moving rapidly in a loose, churning cloud, confusing them and dazzling them with their slightly silvery skin. Their eyes have developed a crude pupil, allowing them to regulate the amount of light entering. The crest, originally used to attract mates (and now useless for that purpose) has stiffened to become something like a dorsal fin.