Blowfish, balloon fish, puffer fish, porcupine fish--whatever you want to call these aquatic animals, they bear an effective deterrent against predators. This X-ray image shows a porcupine fish in its defensive posture--filled with water or air and deploying sharp spikes--and then in its normal, relaxed state.

When inflated, the porcupinefish can reach twice its regular height, and some species are poisonous. It should come as no surprise that these odd creatures have few predators.