A predator that doesn’t heed the pufferfish’s warning may be in danger of choking to death on the spiky, spherical fish. But the pufferfish’s defenses don’t stop there: Many species are highly poisonous. Certain pufferfish contain the neurotoxin tetrodotoxin, mostly concentrated in the fish’s liver, gonads, and skin. Although this potent toxin can kill some predators (including people), others, such as sharks, are able to withstand a pufferfish meal with no ill effects