Porcupinefish belong to the family Diodontidae and are often lumped together with pufferfish from a different family – the Tetraodontidae.
Both families are toxic. Porcupinefish have poisonous skin secretions, although they employ an even better trick to thwart off would-be predators. When threatened, they may suck in either water or surface air to expand their stomachs 10-fold, which causes very sharp spines to extend perpendicular to their round bodies.
I have seen a freshly-suffocated large escolar fish with an inflated porcupinefish in its mouth.
We have a few porcupinefish species, with the most common and spectacular being Diodon hystrix, which can grow to three feet in length. These fish are circumtropical in distribution, preferring shallow reefs or quiet lagoons.
Fused teeth form a beak, which is well-suited for feeding on shelled prey like bivalves, sea urchins, and hermit crabs.
Tom Byrnes is the owner/operator of Cayman Marine Lab. He acquired his Coast Guard Captain’s Licence when he was a teenager and worked as a commercial fisherman in his youth. He got his first diving certificate in 1974 with the YMCA. He has worked in the local dive industry for more than 35 years and has a PhD in marine biology.