Trunkfishes, Cowfishes: Boxy But Cute!

About one inch in diameter, this juvenile smooth trunkfish maneuvered its way around a reef in Bonaire.

WHAT’S MORE ENDEARING THAN WATCHING A TRUNKFISH SWIM? Watching a baby trunkfish jiggle about trying to.

Trunkfishes at their best are relatively inept swimmers, with bulky, triangular bodies and limited tailfin  propulsion. They row furiously, they move slowly and awkwardly.

As juveniles, they’re small and round. Their tails are barely there, almost negligible, making for less control, with a certain amount of yeeing and yawing. It’s both irresistible to watch them work to master their control – and a little guilt-inducing for being charmed by the effort.


A smooth trunkfish works the sponges and algae on the hull of a wreck.


The two most prevalent species of trunkfishes in the Atlantic/Caribbean basin are the smooth (Lactophrys triqueter) and spotted (L. bicaudalis) trunkfishes. A third is the somewhat less-seen Buffalo trunkfish (L. trigonus). There’s also a “golden” variation of the smooth trunkfish – still an L. triqueter – although it’s found only in the at Flower Gardens National Marine Sanctuary in the western Gulf of Mexico and at the Bay Islands of Honduras.

Like a negative image of its smooth cousin, this spotted trunkfish cruises the reef.

Close cousins in the Atlantic/Caribbean include honeycomb and scrawled cowfishes (Acanthostrac polygonia and A. quadricomis, respectively). Their “horns” – sharp spines over each eye – make them cowfish. Whereas trunkfishes tend to be from six to 12 inches in length (probably most often seen at about six), cowfishes can grow up to 15 inches in length.


They’re all members of the boxfish family – Ostracomis. With about two dozen species worldwide, boxfishes are also present in the Indo-Pacific basin, many with striking colors and patterns. Members of the Lactoria genus carry the cowfish characteristic of horn-like spines over their eyes.

But none of the I-P species are as singular as the tropical Atlantic-Caribbean trunkfish and cowfishes, with flattened undersides that reinforce their angular architecture, shaped somewhat like Soap Box Derby entries.

Honeycomb cowfish, “horns” and all.



The boxfish term isn’t just related to their shape. Their exteriors of hexagonal scales are fused to an underlying structure of six-sided bony plates, encasing the fishes’ bodies in “boxes” sometimes compared to the shells of turtles. These are armored fishes, difficult for predators to deal with.

On the other side of the equation, boxy protection limits propulsion. Although their dorsal and pectoral fins are relatively large, they don’t provide much power. Protruding from armored torsos, their tails are relatively short. While their tailfins are relatively large, overall they’re limited in range and they propel themselves mostly with furious movements of their dorsal, anal and pectoral fins.


In terms of coloration, they do stand out – the adult smooth trunkfish black with white spots, the spotted trunkfish while with black spots, the honeycomb and scrawled cowfishes rich patterns of contrasting hues. Although not present in black and yellow juveniles, smooth trunkfish tend to acquire a honeycomb pattern of their own in their mid-bodies. Spotted trunkfish don’t have this characteristic.

Spotted trunkfishes also have sharp spines in front their anal fins, smooth trunkfishes don’t (which, perhaps, makes them “smooth”).

This smooth trunkfish does its thing in the sand – scrounge for small mollusks, crustaceans and other goodies.


The mouths of all Ostracoms share two characteristics: powerful jaws, the kind used to crack the shells of mollusks and crustaceans, and protruding lips that look like they’ve been over-blasted with botox. Presumably, those lips facilitate their technique of blowing away bottom sediment with a jet of water to expose the prey that make their diet – worms and the aforementioned mollusks and crustaceans. They’ve also been known to bite off pieces of coral to get at polyps and to expose underlying prey.

In reality, they’re omnivores, which means they’re also known to feed on sponges, tunicates. Sea cucumbers and sea urchins and to graze algae and sea plants. In fact, most times I’ve observed them, they’ve appeared to have been grazing on algae, not blasting away bottom sediment.

Scrawled cowfish, photographed at Flower Gardens in the Gulf of Mexico.


Trunkfishes and cowfishes have one other line of defense, one not so obvious watching them putter around the reef. When stressed, as in touched or attacked, they exude ostracitoxin, a poisonous substance known to be potent enough to kill nurse sharks. It has to be ingested to be toxic, so a diver near them doesn’t have a problem. Grabbing them and trying to kiss their pouty lips, however, would be a bad idea. Actually, it would be a bad idea anyway; see the part, above, about powerful jaws.

Also a bad idea would be collecting them for your aquarium. Collectors who have done so have found the toxin kills off all their other fishes, and, since it’s concentrated in a confined space, the trunkfish itself.

PRINCIPAL SOURCES:  Reef Fish Identification Florida, Caribbean, Bahamas, Paul Humann, Ned DeLoach; Reef Fish Identification, Tropical Pacific, Gerald Allen, Roger Steene, Paul Humann, Ned DeLoach; “Trunkfish,” International Wildlife Encyclopedia, Maurice Burton, Robert Burton;  Species of the Week: Smooth Trunkfish,” Bermuda Biology; “Spotted Trunkfish,” Mexico – Fish, Marine Life, Birds and Terrestrial; Spotted Trunkfish,”