Few fish are cuter than a fully expanded, portly pufferfish — but don't be fooled. The pufferfish is the second most poisonous vertebrate on the planet. Fishermen recommend the use of thick gloves to avoid poisoning and the risk of getting bitten when removing the hook. The poison of a pufferfish, which has no antidote, kills by paralyzing the diaphragm, causing suffocation.
Nearly all pufferfish contain tetrodotoxin, a substance that makes them taste bad (and sometimes lethal) to fish. According to National Geographic, tetrodotoxin is deadly, up to 1,200 times more poisonous than cyanide. One pufferfish has enough toxin to kill 30 adults.