In the beginning, a pufferfish seems miserable yet they seem to adapt to the tropical waters because that is where it makes its home. There is an order of fishes called Tetraodontidae that the pufferfish are a part of. Tetraodontidae are tropical fish and the closest relative of a pufferfish, species such as triggerfish and tripodfish. There may be other ways to trace the development of the pufferfish’s anatomy but using the evolutionary tree is definitely one of the best ways to do so. Along the way, you can see how the exceptional trait of pufferfish inflation started from nothing, just a simple cough, according to a Florida State University biologist by the name of Peter Wainwright. Today’s tripodfish is very much like the first tetraodontiforms to branch away on their own. When it comes to coughing, Wainwright only found minor changes. Their mouths are smaller than most fish. They keep their mouths open for a fifth of a second to let more water into their gills before they close them and then they squeeze their cheeks in.
Although these changes are minor, a smaller mouth certainly a stronger effect on the flow of water in a cough. According to Wainwright, to get a more directed and managed flow, you have to exhale the same volume of water through a small aperture, which can be aimed and has a higher velocity. Normally, pufferfish pump up themselves by taking approximately 35 gulps in about 14 seconds. Thanks to some peculiar anatomic changes in their bones and muscles, every gulp draws in a huge load of water. To pull in more water, all a pufferfish must do is open its mouth and then rotate its shoulders back and increase the size of its mouth cavity. Like a seal, once a pufferfish has taken in water, their gill slits clamp shut and a powerful valve flips up over the inside of its mouth. When a pufferfish compresses its mouth cavity, instead of the water flowing out of its gills or mouth, it runs down its esophagus.