Porcupinefish, a type of Pufferfish are a regular sight whilst diving in The Andaman Sea. There are over 120 species of Pufferfish in all, and you can easily see several of them when diving at our regular Scubafish dive site, Ko Haa. But everyone’s favourite is the cute and curious Porcupine Puffer. These friendly fish boast large, bulbous eyes and a mouth which looks like they’re smiling. Add to this their nosy natures (often getting very close to divers for a better look) and it’s clear to see why everyone loves them.
Porcupinefish, like all Pufferfish, have the ability to inflate their bodies to double their normal size, thus reducing the range of potential predators to those with much bigger mouths. A second defense mechanism peculiar to the Porcupine Puffer, is provided by the sharp spines which radiate outwards when the fish is inflated.
Pufferfish know how to inflate themselves instinctively from hatching. When frightened, the Porcupine Pufferfish unhinges his jaw in order to widen his mouth. This allows more room to suck in around 35 large gulps of water in approximately 14 seconds.
If the Pufferfish finds the threat has not gone away once he has sucked in all the water, he moves to the inflation stage. His stomach and skin are highly stretchy and he has no rib cage to get in the way. At the end of his water-sucking, he stops up his mouth with a valve meant to close his esophagus. Using muscles in his body that evolution has developed over time, he “coughs” the water toward the front of his mouth and down the open esophagus into the stomach. This causes him to puff up.
While inflated, a pufferfish loses even more mobility so this defensive move is executed because he cannot outrun his enemies. Once he feels the danger has passed, he calms and forces the water out of his stomach in several stages until he returns to his original size. The water is expelled in a reverse of how it entered. Too much air trapped in his stomach can prevent a puffer from expelling the water, which can be fatal.
It is incredibly stressful for the Porcupine Puffer to inflate. This is why as divers and snorkelers, we never touch or too closely approach these super-cute fish, as we have no desire to see them stressed or in the life-threatening situation of finding themselves unable to expel the water. Any dive guide who encourages a Porcupine Puffer to puff up (a practice we have seen) deserves reporting and more – really, they shouldn’t be working in this role if this is how they “entertain” their customers.
The higly poisonous Porcupine Pufferfish
A predator that manages to snag a Porcupine Puffer before it inflates won’t feel lucky for long. Almost all pufferfish contain tetrodotoxin, a substance that makes them foul tasting and often lethal to fish. To humans, tetrodotoxin is deadly, up to 1,200 times more poisonous than cyanide. There is enough toxin in one pufferfish to kill 30 adult humans, and there is no known antidote.
Amazingly, the meat of some pufferfish is considered a delicacy. Called fugu in Japan, it is extremely expensive and only prepared by trained, licensed chefs who know that one bad cut means almost certain death for a customer. In fact, many such deaths occur annually. Who would think that anyone would even want to risk eating this fish? We’ll say it again – the underwater world and its inhabitants are truly amazing and the species known as Homosapien is often truly ridiculous.