Tag Archives: pufferfish

Puffy toylike fishes aren’t to be played with

Published September 23, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

Boxfish are named for their rectangular shape, formed by a rigid shell around the body. Only the fishes’ eyes, fins, mouths and tail are movable. Boxfish ooze a poison to ward off predators. Courtesy Russell Gilbert

My 10-year-old snorkeling friend Darius shouted, “I see a pufferfish!”

He pointed as we swam at Three Tables, part of the Pupukea Marine Life Conservation District.

I looked at the fish.

“That’s called a trunkfish,” I told him.

But neither of us was entirely right, nor was either of us entirely wrong. The swimming suitcase I called a trunkfish gets the heading “Boxfishes and Cowfishes” in my fish textbook, but adds in parentheses, “Also called trunkfish.”

And Darius wasn’t far off in calling the slow-­swimming fish a pufferfish. Trunkfish and pufferfish aren’t from the same family, but they’re kissing cousins.

No fish, though, wants a kiss from a boxfish. Like its pufferfish kin, boxfish carry a toxin so strong it can kill aquarium mates. And if the little boxfish gets really upset, it can exude, from its skin, enough poison in the tank to also kill itself.

Clearly, boxfish didn’t evolve to live in bowls. In the ocean the boxfish’s slippery toxin repels predators but dilutes fast enough in open water to keep the boxfish unharmed.

Boxfish poison isn’t known to kill humans, as does pufferfish poison, but still, I wouldn’t try licking one. Although some people in Asia eat boxfish, the soapy substance the fish ooze is similar to detergent.

Like pufferfish, blue-ringed octopuses, poison arrow frogs and others, boxfish hire out their chemical weapon production to bacteria. In this classic case of symbiosis, the bacteria get a place to hang their hats, and in return they manufacture sudsy slime to protect their host.

The name boxfish, and trunkfish, comes from the fishes’ rigid, rectangular shell, which covers the entire body like a knight’s armor. Only the fishes’ eyes, fins, mouths and tail are movable. A few bones support the fishes’ internal organs, but evolution has done away with most bones, including ribs.

Hawaii hosts two common species of trunkfish, the spotted boxfish and the thornback cowfish, growing 5 to 6 inches long. It seems as if there are more, because males and females of the same species look different.

The cowfish gets its name from forward-pointing “horns” on its head. When threatened, the cowfish swims backward, keeping its sharp horns facing the intruder. En guard!

Boxfish swim like little wind-up toys, propelling themselves around with amazing speed and dexterity using only side and rear fins. Members of this family eat algae, sponges, worms and small crustaceans.

I don’t fuss over animal names because, to me, as long as the person involved knows what the other person is talking about, well, the name did the job.

I’m looking forward to my next snorkeling excursion with Darius, hoping he spots another pufferfish-trunkfish-boxfish-cowfish. When you see a fish in shining armor, it’s always worth a shout.

Male Spotted Boxfish. Courtesy Scott R. Davis

Female Spotted Boxfish. Courtesy Scott R. Davis

Shoreline gems offer a palatable mystery

Published March 18, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

It’s still unknown how these porcupinefish palates found on the North Shore by a reader change color from white to shades of amber. ©2017 Susan Scott

Last week, reader Chris emailed a photo of some caramel-colored nuggets that she and husband Matt found along a North Shore coastline. Some of the pebblelike pieces are symmetrical, with a centerline. Others are halves of these, and all bear the markings of former ridges.

The ocean had rotated and polished the stony bits into jewels, lovely as the gemstones we call tiger’s-eye. Chris wondered if I knew what they were. I did not — and the search was on. Chris, Matt and I looked in books, queried friends and searched the internet.

The couple’s friend guessed their finds might be parts of parrotfish throats, called pharyngeal mills, that grind up coral rock. They aren’t, but it gave Chris and Matt a search subject that produced a link from Sydney’s Australian Museum. Pictured there is what the museum identified as a spiny pufferfish palate from a beach in the Gulf of Carpentaria.

Hawaii hosts a pufferfish with spines that we call a porcupinefish. The largest grows to a whopping 28 inches long and weighs 17 pounds, 12 ounces (the state record).

Chris and Matt wondered why porcupinefish mouth parts would be concentrated in one area of a long beach.

It’s possible that porcupinefish are abundant in that part of the ocean, but it’s more likely that the deposits are a result of coastal currents. The ocean sorts pebbles and shells according to flow strength, shoreline shape and objects’ weights, and that area is where the water drops off its palates.

I wondered why the roof of the mouth of the big prickly fish outlasts other parts of its skeleton, but I didn’t wonder for long. I have found dead, desiccated porcupinefish on beaches and brought them home.

When I picked one up to examine its palate, the whole thing fell apart, jaw bones included. That made clear that the fish’s upper tooth, shaped like a curved razor, is fused to a ribbed rock-hard palate. The same-shaped lower tooth is also fused to an identical hard floor, an upside-down palate. Both are bone white.

Apparently, after a pufferfish dies, ocean tumbling wears away its softer bones and teeth, leaving only the solid, durable plates. Where they get their rich color is a mystery.

Porcupinefish use their formidable teeth and rock-hard palates to crush snails, sea urchins and crabs. Be wary of a trapped porcupinefish. If caught or cornered, the fish can easily take off a finger, bone and all. Of the fresh bite I once saw, the remaining forefinger was sliced as clean across as if done with a cleaver.

Chris and Matt invited me to come see their pufferfish palates and, seeing my awe, generously gave me a few. Forget diamonds, rubies and sapphires. For us, porcupinefish palates are far more precious than stones.

Puffer fish armed with toxin in addition to its spiny body

Published October 5,, 2015 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2015 Susan Scott

A dead ulua, or jack, washed up on Kailua Beach recently after having tried to ingest a porcupine puffer fish, which inflated and stuck in its throat. ©Greg Turnbull

A dead ulua, or jack, washed up on Kailua Beach recently after having tried to ingest a porcupine puffer fish, which inflated and stuck in its throat. ©Greg Turnbull

Kailua resident Greg Turnbull sent a picture of a freshly dead, 36-inch-long fish he found on Kailua Beach during a recent dawn walk. Greg thought the fish was an ulua (jack), and I agree. Although it’s unusual for a big jack to wash up on an Oahu beach, that’s not what drove Greg to take the picture. The gaping ulua had an inflated porcupine puffer fish stuck in its throat.

The puffer fish made a fatal mistake. Swelling up in a predator’s throat is a good ploy to prevent being swallowed, but step two is crucial. The puffer must shrink and run before the suffocated fish washes ashore.

People call the 120 or so species of puffer fish several names — balloon fish, blowfish, globefish, toadfish — all referring to their famous defense: an elastic stomach. When threatened, a puffer engorges its stretchy stomach with water or, if a predator drives the puffer to the surface, air.

Susan holding a puffer fish. Courtesy Craig Thomas

Susan holding a puffer fish. Courtesy Craig Thomas

The idea is to grow too big for a predator’s mouth. If the pursuer has a really big mouth, the puffer sticks in the fish’s throat. Because fish breathe by taking water in the mouth and expelling it out the gills, a throat full of puffer fish is deadly.

Another deadly puffer defense is the ability to store a poison called tetrodotoxin. In the ocean, puffers eat plants and animals that contain naturally occurring bacteria that manufacture tetrodotoxin. By choosing food that doesn’t contain those bacteria, aquaculturists can raise poison-free puffer fish.

Tetrodotoxin is well known for being so potent that a tiny dose can kill a person in minutes. The poison blocks sodium channels in nerves, and when sodium can’t enter a nerve cell, it can’t tell muscles what to do, such as breathe. There’s no antidote to the toxin, but, because it wears off by itself, artificial breathing can save a victim.

Ulua (Jack). Courtesy Russell Gilbert

Ulua (Jack). Courtesy Russell Gilbert

So, I wondered, are jacks immune to tetrodotoxin?

Hard to say. Puffer fish have been found in tiger shark stomachs, and the Internet has pictures of a snapper, frogfish, loggerhead turtle and duck eating a puffer fish, but it’s unstated whether the animals lived or died. What I did learn, however, is that the sodium channels in some snails, crabs and presumably tiger sharks are unaffected by tetrodotoxin.

I also learned in my reading that 19th-century warriors from the Gilbert Islands (today Kiribati) wore what a British explorer in 1847 called “an extraordinary looking apology for a helmet.” The illustration shows a porcupine puffer fish skin on the head of a warrior. Apparently the man mistook a fish for a hat.

Thanks, Greg, for sharing your picture. It’s great food for thought.


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2015 Susan Scott