Pufferfish are cute, and most pufferfish are toxic. Like people, they spend their weeks moving between states of puffed up and deflated. Or, really, three states: normal, puffed up and then the hangover after the puffing up. Ironically, the pufferfish toxin, called tetrodotoxin, is deadly because it stops a person’s diaphragm from moving – in other words, it stops you from being able to puff yourself up. And you could see that as a lesson for wanting to eat them in the first place.
You’re wondering what is inside a blown-up pufferfish, how they inflate. Firstly: it is not air, or else they would pop up and out of the water like a balloon in a swimming pool. Also, air is hard to come by down there. They turn themselves into absurd-looking spherical objects by sucking water – something called, grossly, “buccal pumping” – into their extremely elastic stomachs. They don’t have ribs, which helps. This gives predators a fright – but perhaps more to the point, large spheres are hard to swallow.
