This is a very interesting question, and to figure it out, you need to figure out two questions first: first, why does the pufferfish bulge? Second, why does a bulging balloon break when you poke it with a needle? After that, let's look at the two core questions: will the pufferfish explode when poked with a needle after it bulges? If it doesn't explode, what happens?

Why does a blowfish bulge?

The puffer fish is commonly known as blowing belly fish, air drum fish, it is not the name of a kind of fish, but under the triggerfish under the family of two, three, four-toothed triggerfish, as well as the box trigger family under the fish collectively, they are widely distributed in the world's temperate and tropical sea water and fresh water, there is a **** the same characteristics: can be inflated body.

The pufferfish's body expands like a round balloon, which is an important means of defense against predators. Because the pufferfish swims slowly with only its pectoral fins involved in propulsion, and because of its small size (about 15 centimeters on average), the pufferfish is a more desirable predator for many aquatic animals.

Over the course of its long evolution, the pufferfish has developed a defense mechanism that expands its body so that predators that would otherwise be able to swallow it in one gulp will give up hunting because of its larger size. Of course, the pufferfish's defense mechanism is not only body expansion, like the spiny pufferfish under the family Pufferidae, there is also a layer of dense spines on the surface of the body, which is a nightmare for the predators when it expands (zipping mouth).

When the pufferfish is frightened, it will expand its body, the specific method is to use its mouth to inhale a large amount of water or air into the stomach, exactly the air sac of the stomach, this air sac is a part of the stomach, in the shape of a pouch, when a large amount of water and air enters the air sac, the air sac begins to expand violently, at the same time, its gill slits are all closed, and the valves are also pushed up to the back of the mouth along with the expansion of the air sac, which forms a "door", so that the whole pufferfish becomes airtight. The skin of the pufferfish is also strongly contractile, so it also expands until it becomes a "ball". Upon contact with danger, it opens its gill slits and valves, releasing water and air again, and a normal pufferfish emerges.

Why does a balloon explode when stuck?

The balloon will usually explode into balloon fragments if it encounters something sharp, which is caused by two reasons***:

First, internal and external pressure. Although the balloon inside and outside are air, but when we blow up the balloon, we use the force is several times our normal blowing, this is because the balloon is elastic, in our blowing, the balloon will also be pressed back, so that the balloon inside the formation of the outside world than the air pressure is slightly larger. When the balloon is pierced by a needle, the gas will desperately push out from the small hole, which will widen the hole, and then it bursts.

Second: tension. After the balloon expansion, the surface tension becomes larger, in the case of non-destructive, the balloon is round, but if a needle pierced a small hole, at this time all the force will be concentrated in the small hole, after the tension is concentrated, the balloon will naturally burst.

Of course, there is another reason why the balloon will burst if it is stabbed with a needle, and that is because the balloon is thin enough. Because if I take a needle and stick it down to the point where we made the incision, the balloon doesn't pop, it slowly deflates.

Will the pufferfish explode when "inflated" with a needle?

From the principle of puffer fish expansion, there are two different cases: inhaled water and inhaled air. If the pufferfish inhaled water, with a needle to break, but also divided into two small cases, one is to use a fine needle, in this case, although the pufferfish seems to swell to the limit, in fact, its stomach is still ductile, coupled with the stomach of the water outside the outside world does not have a big difference in pressure, so in the stomach of their own repair, it will not burst, and will not even flow of water. If it is stabbed with a thicker needle, the stomach's ability to repair itself loses its effect, water will flow out of the pinhole, and eventually the pufferfish gradually regains its size and bursts.

If the air is inhaled, the air still creates a pressure difference with the outside world in the pufferfish's stomach, so when it is stabbed a little with a fine needle, the gas will gradually leak out of the small hole, but under the repair of the stomach and the skin, this small hole will soon be plugged, and at this time the pufferfish reduces a little.

If air is inhaled, and a thicker needle is used to stab it, the gas will continuously leak out from the large hole, but there will not be an explosion, because its air sac can still be extended.

Of course, there is another situation where nothing will happen because the pufferfish's body surface is a layer of rough epidermis, and if your needle doesn't even penetrate this layer, it won't hurt its air sac at all. I remember watching a Japanese video on how to handle a puffer fish, in which the chef easily removed the skin with a knife, and there was muscle tissue underneath, so if you didn't pierce it y enough, you wouldn't hurt it at all.

Summary

The reason why a bulging balloon with a needle will break is because the balloon is originally very thin after expansion, and its internal and external pressures are also different, and when it is pierced, the gas rushes outward from the small holes with a brain, which will inevitably burst the balloon. However, the puffer fish is different, it is still under the bulge of the air sac with toughness and ductility, coupled with the living tissue cells are self-healing ability, so with a small needle, will only leak a small amount of water or gas, with a thick needle, water or air will run out of the brain, and will not appear to be the case of an explosion.