Salt marshes are home to tiny crustaceans called amphipods that keep a low profile: Their gray-brown coloring helps them blend in with their surroundings, and they spend most of their time hiding under vegetation. But when amphipods are infected with a parasitic worm called a trematode, they turn bright orange and lose their tendency to run for cover when exposed. This bizarre behavior makes them stand out to predators—as well to scientists.
