A stingray lies on the seafloor like a moving patch of sand, yet it carries a venomous weapon in plain sight. Its disc-shaped body, pectoral fins spread wide, lets it hug the bottom and stir up sediment, turning its outline into visual noise for passing predators and unwary swimmers above.The apparent harmlessness ends at the tail. Many stingrays have a barbed spine embedded in the tail, connected...More