Which Fish Can Puff Itself Up When Threatened? Pufferfish

Q: Which fish can puff itself up when threatened?

The pufferfish (also called blowfish) can inflate its body to several times its normal size when threatened. It quickly gulps water into a very stretchy stomach, turning into a round ball that’s hard for predators to swallow. Many pufferfish also carry tetrodotoxin, one of nature’s most powerful poisons.

How the puffing works

A pufferfish has an elastic stomach and no ribs to stop it expanding. When frightened, it pumps water into its stomach in rapid gulps. If pulled out of the water, it may gulp air instead, which can harm it. Once the danger passes, it slowly lets the water back out.

Puffing takes a lot of energy, so it’s a last resort. Pufferfish are slow swimmers and rely on it when they can’t escape.

A deadly defense

Fact	Detail
Toxin	Tetrodotoxin, which blocks nerve signals
Strength	Often described as more than 1,000 times as deadly as cyanide
Where it comes from	Bacteria in the fish’s diet, not the fish itself
Antidote	None known; treatment is supportive care

Pufferfish raised in captivity on a controlled diet can be non-toxic, which supports the idea that the poison comes from food.

Fugu: a risky delicacy

In Japan, pufferfish called fugu is eaten as an expensive dish. Only chefs with a special license, requiring years of training, can prepare it by removing the poisonous organs such as the liver and ovaries. Japanese law has banned serving fugu liver since 1984.

Pufferfish vs porcupinefish

	Pufferfish	Porcupinefish
Skin	Smooth or with small prickles	Long sharp spines that stand up when inflated
Family	Tetraodontidae	Diodontidae

Underwater artists

In 1995, divers off Japan found mysterious circular patterns in the sand. Years later, scientists discovered the artist: a male white-spotted pufferfish that spends about a week sculpting a detailed ring up to 2 m wide to attract a mate.

For more ocean animals, see which sea animal can change color and what the largest sea turtle is.