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The Explorer's Guide contains a treasure trove of aquatic science resources developed for use in K-12 classrooms. Back to Explorer's Guide.

Porcupinefish Scientific Name: Diodon hystrix
Porcupinefish suck up water to scare predators. The thick, leathery skin of porcupinefish is covered by scales that have been modified into spines. They are extended when the porcupinefish gulps down water to puff out and sticks a hungry predator.

Region: Philippines

Shaped like a short baseball bat, the porcupinefish doesn’t seem like a fierce creature. Looking closer, it is found to be quite dangerous. The scales of this fish are modified into long spines, which generally lie flat against the body. When frightened, porcupinefish quickly gulps down lots of water. This makes the fish expand like a balloon—doubling and even tripling in size. As the porcupinefish puffs up, the spines on the skin stick straight out, making this fish even harder to eat. After the frightened predator swims away, the porcupinefish lets loose all the water inside its body, getting back to its normal shape and size.

This fish can be up to 3 feet (1 m) long, which would be quite a display after puffing out its entire body into a ball shape.

Porcupinefish live in the caves and holes of lagoon and seaward reefs at depths of 7 to 167 feet (2 to 50 m). Generally they can be found either resting in a reef hideaway or swimming out in the open over the reef.

Juveniles and occasionally adults may live in the open ocean floating around within the safety of Sargassum weeds, which is a leafy golden brown algae that floats freely throughout the ocean with small air bubbles or bladders. Catching a free ride inside these weeds allows the porcupinefish to be found in all the tropical oceans.

Porcupinefish live in the warm parts of all the warm Oceans.

At night, the porcupinefish searches for hard-shelled sea urchins, snails and crabs. “Diodontidae", the Family name of this animal, means “two-toothed". This refers to the hard beak-like jaw that the porcupinefish uses to crush its crunchy prey. Sometimes this fish will also eat sea jellies.

At sunrise or sunset, porcupinefish pelagic spawn, which means they mate in an area where the fertilized eggs will be taken away on the currents to drift into the open ocean. Pairs may spawn together, or a group of males will spawn with a single female. After the eggs hatch, the larvae float in the epipelagic zone or the zone in the open ocean near the surface. When the small fish grows to a certain size, it will swim down and become a member of a coral reef.

>A species or group of organisms that is in danger of extinction or disappearing from the face of the earth in the near future if its situation is not improved.

A species that can be found throughout its natural range but is declining in number and may become endangered in the absence of special protection efforts.

A species that is not declining in number but is of special concern because it is sensitive to pressure by particular human activities or natural events.

A species that is not declining in number and is not sensitive to pressures by human activities or natural events.

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Threats and Management
These fish are sometimes sold to souvenir shops, where the porcupine fish are lacquered in their puffed up state. Otherwise, they are not highly sought after because their organs are poisonous. The poison in the fish actually comes from a type of toxic algae that the porcupinefish eats.

Skilled Japanese chefs prepare porcupinefish and boxfish, which is called fuga, in a way that retrieve the meat and almost all the poisonous parts are cut out. A slight amount of poisonous meat is left to be served with the safe portion. The diner feels somewhat woozy after eating the fuga. Prepared in this way, these fish are considered a delicacy. On occasion, a person eating the fuga dies.

While porcupinefish are taken for souvenirs and occasionally to eat, there hasn’t been an overabundance of them taken from the oceans. Their population remains stable.

Did You Know?
As another defense mechanism, high levels of poison are concentrated in the porcupinefish’s gonads and liver. Most predators will remember getting sick from eating a porcupinefish and won’t try it again.

Few animals will eat porcupinefish. Tiger sharks, which are known as the garbage cans of the sea because they eat just about anything, will eat adult porcupinefish. Juveniles are eaten by large billfish like dolphinfish and tuna.

Web Sites:
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Print Publications:
Debelius, H. 1999. Indian Ocean Reef Guide. Frankfurt, Germany: IKAN. 321p.
ISBN# 3-9317-0267-7.

Hauser, H. 1984. Book of Marine Fishes. Houston, Texas: Gulf Publishing Company. 192p. ISBN# 1-55992-025-4.

Hoover, J.P. 1993. Hawaii’s Fishes. A Guide for Snorkelers, Divers and Aquarists. Honolulu, Hawaii: Mutual Publishing. 183p. ISBN# 1-56647-001-3.

Kuiter, R.H. 1998. Photo Guide to Fishes of the Maldives. Australia: Atoll Editions. 257p. ISBN# 1-876410-18-3.

Myers, R.F. 1999. Micronesian Reef Fishes. Barrigada, Guam: Coral Graphics. 216p.
ISBN# 0-9621564-4-2.

Perrine, D. 1997. Mysteries of the Sea. Lincolnwood, Illinois: Publications International, Ltd. 312p. ISBN# 0-7853-2430-5.

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Vocabulary Words

Epipelagic zone – The zone of the open ocean near the surface.

Extinction – An organism that has not been present on the face of the earth for over 50 years.

Organism – A living thing.

Pelagic spawners – Fish that gather in an area in the ocean where the fertilized eggs will be taken away on the currents to drift into the open ocean.

Sargassum weed – A leafy golden brown algae that floats freely throughout the ocean with small air bubbles or bladders. This algae can house many small animals like small fish, worms, shrimp, crabs and jellies. Some of these animals only live within the safe confines of the Sargassum weed.

Species – A group of organisms capable of breeding and producing fertile offspring; organisms that share the same gene pool.

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Porcupinefish (Diodon histrix) Copyright Shedd, Edward G. Lines
Porcupinefish (Diodon histrix) Copyright Shedd, Edward G. Lines

Porcupinefish (Diodon histrix) Copyright Shedd, Edward G. Lines
Porcupinefish (Diodon histrix) Copyright Shedd, Edward G. Lines

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