Slender-spined porcupinefish an expert in defence


Bec Crew


Bec Crew

Bec Crew is a Sydney-based science communicator with a love for weird and wonderful animals. From strange behaviours and special adaptations to newly discovered species and the researchers who find them, her topics celebrate how alien yet relatable so many of the creatures that live amongst us can be.
By Bec Crew 19 February 2015
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Just like a porcupine, this fish has spines that spring up to defend itself from predators

OH, HELLOW THERE, slender-spined porcupinefish. Are you selling something? Knives? Cookies? A timeshare at the Gold Coast? Doesn’t matter, I’ll take it all, I just want to make you happy, because look at that little face!

Found in the shallow coastal waters of southern Australia, most commonly in Port Phillip Bay in Victoria and around Tasmania, the slender-spined porcupinefish (Diodon nichthemerus) is one of the smallest members of the porcupinefish family, Diodontidae.

Usually growing to around 15cm long, the species has been given some adorable nicknames to match that sweet little smile – the globefish, the balloonfish, and of course, the blowfish.

Being relatively small in the ocean is as good as a death sentence, so the slender-spined porcupinefish has evolved an entire arsenal of defence mechanisms to keep it out of the jaws of larger organisms.

Porcupinefish has arsenal of defence

It’s covered in long, yellow spines that look just like a painful set of porcupine quills (or a sparse head of golden hair), and if those fail to deter a hungry mouth, it can blow itself up to nearly double its regular size. This means that hungry mouth is going to have to recalculate just how much it can swallow, and if it really wants to try, it’s going to have to get those now-fully erect spines down too.

And on top of all that, if you get stuck by one or more of those fully erect spines, you’re going to be hit with a nasty dose of tetrodotoxin, which is a super-potent neurotoxin produced by several species of porcupinefish, pufferfish, newts, ocean sunfish, and the blue-ringed octopus. Not only is tetrodotoxin deadly to large and small sea creatures alike – bottlenose dolphins should know never to eat a porcupinefish – we’re not immune to its strength either. Scientists have calculated that it’s 1200 times more poisonous than cyanide.

But I know what you’re thinking – inflating oneself looks awfully tiring, is there a limit on how many times the little slender-spined porcupinefish can do that before it all becomes too much? The answer, according to Jeff Leis, a Senor Fellow in the Ichthyology Department of the Australian Museum, is no:

“The inflation of porcupinefishes is a defence measure, and, as such, there is no limit to the number of times an individual can inflate (and deflate). If the fish inflates at the surface, it is likely to ingest air. Air can be difficult to expel, and can lead to death of the fish as the fish floats and cannot leave the surface. However, if the fish inflates under water, it ingests only water and has no problem deflating once the danger has passed.”

No wonder that little guy up there is wearing such a coy smile. It knows it can kill us all a million times over. Yes, slender-spined porcupinefish, I’ll buy whatever you’re selling, but now it’s for entirely different reasons…