What are barnacles, anyway? They may look like lifeless rocks, but there are actually animals inside! Within the cone-shaped shells are crustaceans who are related to crabs, shrimp, and lobsters. One of the most impressive things about these sea critters is their ability to attach to a surface of their choice—and hang on. The adhesive they produce is one of the strongest natural glues known. Its tensile strength? 5,000 pounds per square inch. And the adhesive strength? About 22-60 pounds per square inch. They are a successful group, with over 1,000 different species inhabiting diverse waters all around the world.
Photo: Mark A. Wilson