Defense and camouflage among sea creatures

   In a world of hungry hunters, each species must work out its own means of defense and attack. Some, like the tuna, shark, and barracuda, have the implements of sheer power—sharp teeth, swift reflexes, speed and strength. The sawfish waves before him a long saw-nose, equipped with two rows of bony "teeth." He swims into a school of smaller fish and hacks them to pieces.
   The slow-moving snails, clams, and oysters try to escape their foes by retreating into their shells.
Some creatures have special and unusual defenses. Squid, octopi, and some shrimp blind their enemies by discharging dark "ink" into the water around them.
   Jellyfish and sea anemones have coiled, hollow darts with which they can inject poison to paralyze their attackers. Sting rays have poisoned spines on their tails; other rays and some eels can give electric shocks. Sponges lodge tiny spikes in their enemies.
   Certain sea cucumbers can cast off some of their insides. While the enemy pauses over these, the cucumber escapes. Later it grows new parts.
   Flatfish, rackfish, and pipefish, living among the eel-grass and seaweed groves of the shallows close to shore, have forms and colors that make them hard to see among the grass blades.
   Decorator crabs cement bits of seaweed over their shells and legs. The hermit crab, which has a tender rump, shields it by living in a discarded shell. Among such slow-moving creatures, defense is—next to food—the most important part of life.