Everyone loves pretty pufferfish! Here in the Costa Rican Pacific coast we get many species from the very small spotted sharpnose puffer to the colour-changing guineafowl puffer.  Pufferfish are morphologically similar to the closely related porcupinefish which have large external spines, like the Spotfin Burrfish and the Freckled Porcupinefish. 

Pufferfish are most diverse in tropical waters, being absent from cold water environments and porcupinefish, found in temperate and tropical seas have some species found offshore in large schools of thousands of individuals.

Both pufferfish and porcupinefish have a lot in common. Both have fused teeth that form a beak that can be used to crush mollusks and crustaceans.  These slow-moving fish also have the ability to use a combination of weapons to deter predators.  They both (majority of species) have a build up of toxins in their bodies, one of the most potent toxins known to humans, tetrodotoxin, that makes them poisonous to eat. They also have the ability to inflate their bodies if threatened or provoked.  Which is what most people think of when they picture a pufferfish.   

With good eyesight and a fast short burst of speed used as their primary defense mechanism, their ability to puff up is used as a secondary line of defense.  These fish species can, if necessary, can inflate their bodies by filling their highly elastic stomach with water (or air if outside the water) thus changing their body shapes from the ‘typical’ elongated fish shape into a balloon or spherical shape. Porcupinefish spines are also moved from a position against the body to a perpendicular one (puffers also have spines but not large visible ones, they are thinner and hidden until puffed) reducing the range of potential predators.  

So why don’t we make all the puffer fish we see when diving/snorkeling puff up for our entertainment? 

Yes the puffing mechanism can deter predators, but it can also be harmful to the puffer fish, maybe even leading to death.  They can inflate pretty quickly but once it’s time to deflate this process takes a lot longer, more than 5 hours on average for the fish to return to its normal metabolic level during which time the fish doesn’t have the same mobility making it more vulnerable.  It is exhausting for the fish to puff up, hence why used as a last line of defense.  Also by expanding its stomach the internal organs are thought to be flattened in the body leading to potentially deadly stress.  

Remember it is bad practice to touch anything underwater, take only photos and leave only bubbles.  

Fun Fact: 

Dolphins have been observed passing puffer fish between them in an apparent attempt to get high!!