Tetrodotoxin is a lethal poison found in the bodies of pufferfish and a great tool against assailants. A single fish contains enough poison to paralyze thousands of predators. In some countries pufferfish is considered a delicacy, and many people have died after eating meat, which was not prepared properly. The Japanse or tiger pufferfish does not secrete the poison, which accumulates in their organs and skin as a consequence of their diet, which includes bacteria that are capable of producing tetrodotoxin. Those who are raised in captivity will have a different diet and tend to lose the toxicity. A team of researchers wanted to learn how captive Japanese pufferfish will react to the poison and enhanced their diets with purified TTX over one month. The results were quite surprising as fish that consumed the toxin were grew longer by 6%, or their mass was up to 24% bigger in comparison to those who enjoyed a nontoxic diet. They were also less aggressive and didn\u2019t tend to bite the fins of other pufferfish as often as the ones in the control group. Since growing rate and aggression are influenced by stress the researchers decided to measure the levels of two hormones associated with stress: cortisol present in blood and a brain hormone known as corticotropin. The fish that received nontoxic food featured higher levels of the two hormones, with the one of cortisol being up to four times higher. Previous research has inferred that pufferfish reared in a hatchery tend are more vulnerable in comparison to their wild equivalents as TTX plays an important role in decision making. Hatchery-reared pufferfish featured a considerably lower level of TTX. There are more than 120 species of pufferfish, with 22 being approved by the Japanese government as being usable in restaurants. The tiger pufferfish is the most popular among many rich customers. Chefs have to take an advanced exam to be able to cook the fish without consequences.