Pufferfishes and Their Relatives

Pufferfishes are well known for their ability to inflate their bodies in the face of danger, but when it comes to the pufferfish family this is just one of many fascinating traits in a truly diverse group of fishes. Pufferfishes and their relatives belong to the order Tetraodontiformes that contains 447 species in ten families. They primarily live in marine habitats from coasts and reefs to open pelagic waters and deep ocean, but some pufferfishes live in freshwater rivers in Southeast Asia, South America, and Africa.  
 
Pufferfishes and their relatives are some of the most diverse fishes in terms of their anatomy and natural history. They range in size from less than an inch long (2.5 cm) to some of the largest fishes in the ocean that can weigh more than 6,000 lbs (2,721 kg) and reach 10 ft (3 m) in length. They can be drab or colorful and some species can rapidly change color. Many also have interesting scales, spines, or other antipredator adaptations such as inflating their stomach with water to increase body size, being covered with stiff, inflexible armored plates, or having powerful toxins. Despite the diversity in their forms and life histories, pufferfishes and their relatives are all united by a reduced skeleton—most fishes have more than 500 bones, but the average tetraodontiform has only about 300. Although pufferfishes and their relatives have been extensively studied, there is still much to discover about their natural history, especially about those that live in deep waters. 
 
Read on to learn about each of the 10 families through a representative from each family below. 
 
Pufferfishes (Tetraodontidae), 196 species 
Pufferfishes are the most famous tetraodontiforms because they can inflate their body several times its ordinary size by rapidly pumping water or air into their stomach. Inflation is a defensive mechanism that allows the fish to appear larger when other fishes or wading birds attack puffers. Pufferfishes are the largest family of tetraodontiforms so four members can be found in the graphic (above) to represent their diversity (each of the other nine families is represented by a single species). 
 
Yellowfin Pufferfish 
Takifugu xanthopterus 
 Species in the genus Takifugu are often known as “fugu,” and are served as a delicacy in Japan. Fugu can have a powerful neurotoxin, tetraodotoxin, that is deadly if consumed. The yellowfin pufferfish is the most colorful species of Takifugu and its common and scientific name reflect the bright yellow fins (xantho = yellow, pterus = winged, Greek). 
 
Smooth Pufferfish 
Lagocephalus laevigatus 
 Smooth pufferfish are found in the Atlantic Ocean – adults are pelagic (meaning they live in the water column) and live offshore, whereas juveniles occur in more coastal areas. Their diet is primarily corals, crustaceans, and fishes. The smooth puffer is poorly studied and little is known about its life history. Even simple questions about how long they live and at what age they mature remain unanswered. Details about their reproduction also remain unknown. 
 
Golden Pufferfish 
Chonerhinos naritus 
 The golden pufferfish is famous in Sarawak, Malaysia cuisine and a statue and annual festival in the town of Spaoh celebrate the importance of this fish to people in the region. It is one of about 30 species of freshwater pufferfishes, the only family of tetraodontiforms that has species that live in freshwater. Since the golden pufferfish was described in 1848, there has been disagreement about the scientific name and more research is needed to resolve this. 
 
Striped Toby 
Canthigaster criobe 
The striped toby was named as a new species by Smithsonian Institution scientist Jeffrey Williams and colleagues in 2012 based on a single specimen collected from the Gambier Archipelago in French Polynesia. It has a distinct color pattern of 12-14 dark stripes along the body. The species is likely very rare because no additional individuals have been collected since. 
 
Porcupinefishes (Diodontidae), 18 species 
Pelagic Porcupinefish 
Diodon eydouxii 
Like pufferfishes, porcupinefishes can inflate their stomach with water when they are threatened. In addition, some Porcupinefishes have much longer spines (sometimes greater than 2 inches) than pufferfishes that become erect when the fish inflates. The pelagic porcupinefish is a beautiful blue color. Unlike other species of porcupinefishes that live on reefs, the pelagic porcupinefish lives in offshore waters. We do not know what it feeds on, but it has reduced teeth, so likely its prey are softer than the hard-shelled mollusks and corals that typical reef porcupinefishes eat. 
 
Three-Tooth Pufferfish (Triodontidae), 1 species 
Three-Tooth Pufferfish 
Triodon macropterus 
The three-tooth pufferfish is the only living member of the family Triodontidae. It can be distinguished from pufferfishes (family Tetraodontidae) and porcupinefishes (family Diodontidae) by its elongated pelvic bone that it uses to flare a large pelvic fan (sometimes called a dewlap). It has a large eyespot on the pelvic fan that may be used to intimidate predators. The three-tooth pufferfish lives at depths of 600 to1000 ft (183 to 305 m) in the Indian and Pacific Oceans. Because of its deep habitat, the species remained poorly known until the 2000s when the Okinawa Churaumi Aquarium in Japan figured out how to successfully catch and transport live individuals to the aquarium for research and display. Through the aquarium’s deep-sea program, scientists have learned about the three-tooth pufferfish’s seasonal distribution, behavior, and diet, and this special fish can be seen by aquarium visitors. 
 
Triggerfishes (Balistidae), 45 species 
Queen Triggerfish 
Balistes vetula 
Triggerfishes get their name from the three spines in their first dorsal fin; the first can be locked in an erect position that allows them to wedge themselves into crevices on the reef and prevent predators from pulling them out. The locking mechanism can be released by depressing the third spine in the first dorsal fin—a “trigger” of sorts. Queen triggerfish are bright blue, purple, yellow, and green. Their prominent teeth fit together like puzzle pieces that they use to bite off and process pieces of hard-shelled prey, like sea urchins, mollusks, and crabs. They also use an unusual water jetting behavior that allows them to reposition prey in the mouth during processing—imagine not having hands to help you eat and then this water jetting behavior makes more sense! 
 
Filefishes (Monacanthidae), 112 
Scrawled Filefish 
Aluterus scriptus 
Filefishes are closely related to triggerfishes, but differ in having only a single spine in the first dorsal fin (mono = one, Latin; acanth = spine, Greek).  The scrawled filefish can rapidly change color to better camouflage themselves or to communicate with other individuals. At night, a scrawled filefish rests by “mooring”: it uses its mouth to grasp sessile organisms to stay in place. 
 
Tripodfishes (Triacanthidae), 7 species 
Silver Tripodfish 
Triacanthus nieuhofii 
 Tripodfishes live in shallow, coastal waters of the Indian and Pacific oceans. Their closest relatives are the spikefishes, which live in deep waters and have a broader distribution.  Scientists are still learning where silver tripodfish occur, with a several new studies reporting that they occur off India where they were previously unknown. Their name comes from the long dorsal spine and the two stiff pelvic fin spines, making them a “tripod.” 
 
Spikefishes (Triacanthodidae), 24 species 
Devil’s Spikefish 
Mephisto fraserbrunneri 
Spikefishes are among the poorest known tetraodontiforms because they live in deep waters of continental shelves that are hard for scientists to sample. Some spikefishes feed on scales of other fishes, a behavior known as lepidophagy (lepido = scale, phagy = eating, Greek).  

The name Devil’s spikefish alludes to its red skin, black lining of the abdominal cavity, and dorsal-fin spines reminiscent of horns. It is known only from 10 individuals, making it one of the rarest tetraodontiforms. The Devil’s spikefish lives on continental shelves and seamounts from Africa to Southeast Asia, but it has never been seen alive in its natural habitat. 
 
Boxfishes and Cowfishes (Ostraciidae), 26 species 
Honeycomb Cowfish 
Acanthostracion polygonium 
Boxfishes and cowfishes have armor-like, hexagonal scales covering greater than 70 percent of their body that serve as excellent protection. The honeycomb cowfish is aptly named for its hexagonal bony plates and bony horns that protrude from the head. Recently, scientists recorded male honeycomb cowfish fighting—first they flash bright neon-blue colors and then charge each other, biting at the undersides suggesting that their amor is not only important against predators but also other cowfishes. 
 
Deepwater Boxfishes (Aracanidae), 13 species 
Ornate Boxfish 
Aracana ornata 
The Aracanidae are the deepwater boxfishes, which are closely related to the true boxfishes (family Ostraciidae) but live in deeper waters. Recently scientists discovered that the ornate boxfish and other members of Aracanidae have a unique swimming mode – and that despite being almost completely enclosed in bony armor, they are highly maneuverable. 
 
Ocean Sunfishes (Molidae), 5 species 
Ocean Sunfish 
Mola mola 
Ocean sunfishes include the largest tetraodontiforms, with the species illustrated here growing to 131 inches (almost 11 feet) and 2900 lbs (1315 kg). Another species, the bumphead ocean sunfish, Mola alexandrini, grows even larger, to 6000 lbs (2721 kg. Ocean sunfish were once thought to be slow, poor swimmers, but new research shows that they arequite fast and can swim at speeds comparable to those of large sharks and tunas. They make deep dives (600 to 2600 ft, or 183 to 792 m) to feed on jellyfishes and other gelatinous prey. Water is colder at depth so after dives, ocean sunfish bask in the sun at the surface to warm up in a form of behavioral thermoregulation.