What do blowfish fill up with

For example, they have specialized muscles that you won't find in most other fish. Some in their mouth, which pump all that water into their stomach; some in their esophagus, to seal off their stomach like a drain plug once it's full; and some in the base of their bellies, which contract to squeeze out water when they're ready to deflate.

But what you won't find inside is even more bizarre. Brainerd: There are a couple characters that are really helpful in their ability to puff up, and one of those is that they don't have any ribs, and another one is they don't have any pelvis. Narrator: In other words, puffers are essentially missing bones. And that's a good thing, because otherwise they'd get in the way of inflation.

In fact, according to Brainerd, if it weren't for these missing bones, puffer fish would probably have never evolved this way in the first place.

And that would be a shame, since puffing up really is a good defense. Consider one old study in which researchers watched birds go fishing. The birds caught 11 puffer fish, but they dropped nearly half of them because the fish started to inflate. But what's more surprising is that the birds left with empty beaks might have been the lucky ones. Because puffers have another, more potent defense up their sleeves. Their bodies are laced with a neurotoxin called tetrodotoxin.

It's up to 1, times more poisonous than cyanide. So poisonous that one puffer fish can kill 30 adult humans. So poisonous that puffers are reportedly the second most poisonous vertebrate in the world, which is why it's also surprising that us humans? We actually eat them.

The fish balloons and the spines that lie on the surface of its skin stick out, making it a highly unattractive meal! These fish also lack some ribs and have no pelvis, allowing them to become ball-shaped without breaking any bones.

When the fish expands, these become hard and the fish becomes a stiff, tight sphere. Although puffers have evolved to suck in water, if lifted out they can sometimes suck in air. In fact, some of them can even inflate to the size of a balloon or a beachball. My friend Wes Dowd is an associate professor in the School of Biological Sciences at Washington State University who currently studies mussels and tiny crustaceans called copepods in tidepools. Much of his training was with fish and he has always been curious about life in the ocean.

He remembers these fish were a lot different than the bass or flounder he usually caught. The yellowish puffer fish had spines around its body, puffy cheeks, and a little beak-like mouth.