BOXFISH BASICS
As befits its common name, the body of the ostraciid
is encased in a boxy carapace comprised of bony plates,
or scutes, most of which are hexagonal in shape. The
scutes have highly mineralized surfaces and a collagen
base that hold the plates together; it has been proposed
that the suture-like interface between the plates allows
for growth and/or accommodates pressure changes that
occur when the fish moves in the water column (Yang et
al. 2015). This carapace has holes from which the eyes,
mouth, small fins, and caudal peduncle protrude. There
are also apertures for the gill openings and the anus.
Because of this bony encumbrance, boxfishes are slow
swimmers that move mainly by sculling with their dorsal
and anal fins. However, if they need a sudden burst of
speed they can employ the caudal fin. Still, they are not
very fast-moving: their maximum speed is around five
body-lengths per second. On the other hand, they are
highly maneuverable and can perform a 180-degree turn
with a radius of almost zero by employing the tail as a
rudder. The fins are also employed, often operating out
of phase with one another to enable deft maneuvering
in the highly complex coral reef environment. So, while
boxfishes may look a bit awkward, they must be doing
something right—according to the fossil record, the fam-
ily has been thriving almost unchanged for the last 35
million years!
The boxfishes have small mouths with thick lips,
giving them a pouting expression, and jaws that are
armed with a single row of conical to incisiform teeth
that are well suited for rasping food from the substrate.
This brings us to their diet. They feed on a variety of
invertebrates and algae. Many specialize on tunicates
and sponges; some possess toxic substances to dissuade
generalized predators. Some boxfishes (e.g., the Smooth
Trunkfish, Lactophrys triqueter) expose buried inverte-
brates by blowing jets of water out of their mouths at
fine substrates, a technique known as “hydraulic jet-
ting.” They are often joined by groups of opportunists
(especially wrasses) who pounce on buried prey that the
boxfishes flush out.
Not only do these fishes rely on armor plating as an
anti-predation mechanism, they also employ chemical
warfare. When stressed, they exude a chemical cocktail
in their slime that includes a potent neurotoxin called
pahutoxin (known in the past as ostracitoxin). Other
tetraodontiforms (like puffers and porcupinefishes) ac-
cumulate toxin in their organs, but boxfishes are unique
in that they release chemicals into the water. However,
their armor and chemical weaponry do not dissuade
some predators from eating them. Tiger and Galapagos
Sharks love to tear into them, and billfishes, Mahi-Mahi
(Dorado), groupers, snappers, and Napoleon Wrasses
are all known boxfish predators.
So, what happens if a boxfish decides to let its
chemical cocktail loose in the aquarium? At concen-
trations as low as 10 parts per million, this toxin can
kill other reef fishes. This is scary when you considerAcanthostracion polygonius, the
Honeycomb Boxfish, hails from the
Western Atlantic, Florida, and Caribbean.
This is a male in glorious nuptial colors.