Underwater ghost: Russian marine biologist and deep-sea photographer Alexander Semenov captured this image of Caprella septentrionalis, also known as the “ghost” or “skeleton” shrimp. The species, which can grow up to 3.2 centimeters long, spends most of its time attached to sea grasses, filter feeding on the microscopic scraps that float by. But when it has to get somewhere, it moves with a measured, high-arching gait similar to that of an inchworm.