Smooth trunkfish | About Lactophrys triqueter

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Went snorkeling in the Caribbean or other parts of the western Atlantic and saw a boxy, polka-dotted fish with a pointy mouth? Congrats, you spotted a smooth trunkfish! A common sight in both the shallows and deeper reefs, this funky species of boxfish is one of my personal favorites.

Keep reading for everything you need to know about the smooth trunkfish, its natural habitat, fascinating habits and more!

Smooth trunkfish appearance

The smooth trunkfish, scientifically known as Lactophrys triqueter, is a member of the Ostraciidae family of fishes. These are known as the trunkfishes, boxfishes or cowfishes, and as their appearance suggests, they’re closely related to species like puffers, blowfish and filefish.

This one’s a typical trunkfish, its name of course having been derived from its boxy appearance, which it owes to its bony carapace. Its snout is pointy and ends in a small, slightly beak-like mouth. At an average size of around 20 centimeters (8″), it’s pretty standard in its family, although apparently specimens of up to 47 centimeters (18.5″) have been recorded.

Smooth trunkfish are generally dark brown to blackish in color, with an array of white spots all over their smooth, spineless bodies. On the sides of the fish, these spots are arranged in a typical, honeycomb-like pattern. The fins are generally yellow and the tail is broad and fan-shaped.

Interestingly, individuals of Lactophrys triqueter have been recorded in some locations that sported totally different colors from the standard: golden with brown-edged white spots. They’re not quite as common as “regular” smooth trunkfish, though; one study recorded them in the Gulf of Mexico. It noted the golden morph was likely the result of a recessive gene mutation.

Name (common, scientific)Smooth trunkfish, Lactophrys triqueter (sometimes Rhinesomus triqueter)
FamilyOstraciidae
SpreadFrom the western Atlantic to the Caribbean Sea down to Brazil
HabitatSandy shallows and reefs down to around 50m
Smooth trunkfish (Lactophrys triqueter) underwater photo in Curaçao

Smooth trunkfish habitat & diet

This species is a pretty common sight throughout much of its distributions. I saw a few during every single one of my snorkel trips and dives off the Dutch Caribbean island of Curaçao! They popped up both in the sandy shallows and on the reef, where they can occur at up to 50 meters of depth.

Rocky and reef environments are the perfect environment for smooth trunkfish, as they feed on small invertebrates. These guys are not picky and will eat anything from worms to small crustaceans, tunicates, sponges and more.

Its pointy snout makes this trunkfish uniquely adapted to finding prey. Most small oceanic bugs are (partially) buried in the substrate, so Lactophrys triqueter has evolved to spray jets of water in order to easily uncover them.

Planning your next snorkel trip?

Smooth trunkfish (Lactophrys triqueter) underwater photo on a Caribbean reef.

Smooth trunkfish facts

Maneuverability

Like many other members of the family Ostraciidae, smooth trunkfish are particularly maneuverable. Their body shape and fins allow them to almost hover in the water and turn 180° like it’s nothing!

This, of course, comes in very handy in the species’ natural habitat. It allows it to swim easily between corals in search of prey

As a food source: ciguatera

The smooth boxfish is sometimes caught for human consumption. I’m not sure how this works in terms of their toxicity, as the species does have the ability to cause an illness caused ciguatera fish toxicity.

Also referred to simply as ciguatera, these nasty (though generally not deadly) poisonings are caused by a dinoflagellate (single-celled organism) scientifically known as Gambierdiscus toxicus, which I think is quite an appropriate name.

Basically, herbivorous species ingest Gambierdiscus, and are then eaten by carnivores like the smooth trunkfish, as well as many others. If you eat the smooth trunkfish, it can potentially poison you, although a 1984 study lists it as “infrequent risk”. Barracuda and amberjack are examples of “high risk” species.

Ciguatera poisoning is pretty common in the Caribbean, but occurs more in certain areas than others. The aforementioned study notes hotspots include the British Virgin Islands, St. Kitts & Nevis, the south coast of St. Thomas as well as Antigua and Barbuda.

In the aquarium

The smooth trunkfish is occasionally caught for the aquarium trade. However, it can pose a problem in the aquarium because, waddaya know, on top of the whole ciguera situation this species also produces its own toxins.

Identified in a 1982 study as a choline chloride ester of palmitic acid, trunkfish produce this toxin in the mucus layer that protects their bodies. What that means exactly doesn’t matter much; what does matter is that it’s deadly to fish and other aquarium inhabitants.

Because the smooth trunkfish apparently begins secreting this toxin when stressed, anyone interested in keeping one would have to make sure theirs lives a darn comfy lifestyle, or it can accidentally kill off all of its tankmates. A large tank would be a must in order to make sure there’s enough water to dilute any toxins.


Sources/further reading

https://www.fishbase.se/summary/Rhinesomus-triqueter.html

Olsen, D. A., Nellis, D. W., & Wood, R. S. (1984). Ciguatera in the eastern Caribbean. Mar. Fish. Rev, 46(1), 13-18.

Pattengill-Semmens, C. V. (1999). Occurrence of a unique color morph in the smooth trunkfish (Lactophrys triqueter L.) at the Flower Garden Banks and Stetson Bank, northwest Gulf of Mexico. Bulletin of marine science, 65(2), 587-591.

Matsuura, K. (2013). Boxfishes (trunkfishes, cowfishes).

Van Wassenbergh, S., van Manen, K., Marcroft, T. A., Alfaro, M. E., & Stamhuis, E. J. (2015). Boxfish swimming paradox resolved: forces by the flow of water around the body promote manoeuvrability. Journal of The Royal Society Interface, 12(103), 20141146.

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