Pufferfish are a common sight here in Quepos; I don’t think I have yet been diving here without seeing at least one, and usually several. There are two commonly encountered puffers here: the Guneafowl Pufferfish (Arothron meleagris) and the Porcupine Pufferfish, of which there are two species occurring locally – the Longspined Porcupinefish (Diodon holocanthus) and the Spot-fin Porcupinefish (Diodon hystrix).
The Guineafowl Pufferfish has two different color morphs, which may occur at different life stages, though we don’t know when or why the color change occurs. One is a purple-black with white spots, while the other is a bright yellow, often with black spots (the fish is also known as the Golden Pufferfish). There is also a transitional stage, where the fish may have patches of yellow alternating with white-spotted black.
Pufferfish are named for their ability to expand their stomachs, swallowing huge amounts of water (or sometimes air) very quickly, causing their bodies to inflate to many times their normal size as a defense against predators. Most species also have spines. Those of most puffers are hidden until they inflate, while the porcupinefish have external spines that are always visible. Either way, when the fish inflates, it turns itself into a spiky and unappetizing ball that is not easily swallowed by a predator.
In addition to this ability, many species of pufferfish carry tetrodotoxin, one of the most deadly toxins found in a vertebrate. This toxin is 1200 times more deadly to humans than cyanide. The amount of toxin found in a fish varies by species, but in some cases a single fish carries enough to kill 30 adult humans. The toxin is produced by bacteria that live in the gut and are found in some of the foods the pufferfish eats; a puffer raised in an aquarium will lack the toxin. The toxin is found in the fish’s liver, intestines and ovaries, and in some cases in the skin.
Note that this is a toxin, not a venom, meaning that the fish does not inject poison through its spines or by biting but that the fish is extremely poisonous if ingested. While the toxin does not reside in the flesh itself, contamination by even a tiny amount from the organs or skin may prove deadly. In spite of this (or perhaps because of it), pufferfish is considered a delicacy in Japan, where it is known as fugu. Properly prepared, it is said to cause some numbness of the lips and tongue, and perhaps a feeling of euphoria. Although regulations vary throughout Japan, in some places chefs must train for two to three years and pass a rigorous exam in order to be able to prepare and serve fugu.
Even with the laws regarding the preparation and serving of fugu, people do occasionally die from eating it. But death is not the only possible result: fugu can cause a variety of unpleasant symptoms, and in just the right dosage it can cause a paralytic state that resembles death. In this state, the victim’s pulse and respiration are slowed, the pupils are fixed and dilated, and consciousness may be altered. This state may lead to death or permanent brain damage due to hypoxia.
There are many old accounts in Japan of people being declared dead while in this state. The stories speak of people retaining consciousness throughout the experience and hearing themselves being declared dead and their relatives weeping. In some cases, accounts say that the person came out of the paralysis in the morgue, during their funeral, or on the way to be buried or cremated. When someone dies of fugu poisoning, it is therefore customary for the family to wait a few days before burial or cremation in case the person wakes up.
Additionally, the toxin has been implicated by Wade Davis, an ethnobotanist with a PhD from Harvard, in the creation of zombies by bokors (witch doctors) in Haiti. In his 1983 book The Serpent and the Rainbow, he describes the process by which a person may be rendered apparently dead by a powder including pufferfish as well as other toxic ingredients, buried alive, then dug up and ‘resurrected’ by the bokor and fed a steady diet of Datura stramonium, an hallucinogenic plant known in Haiti as ‘zombie cucumber’ that can induce a state of psychosis. This process, together with existing beliefs in Haiti about zombies, allows the bokor to enslave and control people for his own profit.
There has been much controversy among scientists about Davis’s methods and conclusions. Nevertheless, his description of how tetrodotoxin is used in this process would certainly seem to lie within the realm of possibility, and should not be dismissed out of hand.
It also seems that humans are not the only animals to make use of this tetrodotoxin, or to enjoy its effects. Dolphins have been observed gently chewing on and passing around pufferfish and appear to become intoxicated by doing so. In this video, they are seen doing exactly that. While there have been no studies demonstrating the precise effects of tetrodotoxin on the dolphin brain, they do seem to be enjoying themselves!