May 2017

The Surprising Little Boxfish

By Roya Eshragh

I think it’s safe to say that we can all think of examples of fashion or designs coming from nature. But what about a car being inspired by a fish? Which fish species would you guess was the muse? While you go through visions of streamlined tuna, sharks, marlin, and other torpedo shaped fish in your head, let me introduce you to the boxfishes, and we’ll get back to streamlining later.

Boxfish belong to the scientific family Ostraciidae which also includes cowfish and trunkfish. They are all closely related to pufferfish, filefish, and lots of other oddly-shaped, oddly-swimming beasts.

They have scales shaped like hexagons which fuse together to form a box or triangular carapace “shell” from which the fins, eyes and mouth poke through. The edges of the box form keels that run the entire length of the fish in either a cube (true boxfish) or triangular prism shape (trunkfish). This makes them incredibly stable, but generally slow moving, lazing about on reefs or in shallows using their dorsal and anal fins to propel themselves forward. Pectoral and tail fins are used to steer more than for forward motion.

You can find boxfish in most of the oceans, including the Atlantic, Indian, and Pacific. They can be found from Canada to Brazil, but are usually common in the tropical latitudes. They are common reef fish in the Indian and Pacific oceans. They feed on small invertebrates such as molluscs, polychaete worms, small crustaceans, sponges, tunicates, acorn worms, and sometimes benthic algae and foraminiferans. They blow jets of water in the sandy substrate to extract small invertebrates from their homes, but can sometimes eat small fish if available.

Their hard bodies make them difficult prey for many predators, but boxfish don’t stop there. They also have an unusual chemical defense mechanism as well. They secrete toxic mucus from their skin when stressed which is chemically similar to soapy detergents. These can interfere with receptor-mediated processes of ocean-dwelling animals and are generally bad for the reef whether natural or in urban runoff. These chemicals are unique in fish, but similar to steroidal saponins (which essentially means hormonal soap) released by sea cucumbers and red tides. This combination of body armor and poison leads to very few natural predators.

As such, boxfish aren’t known for their speed and allusiveness. They don’t have to be! However, as unintuitive as it seems, boxfish are some of the most mobile and agile fish in the oceans. So much so, that Mercedes-Benz created a concept car inspired by the adorable yellow boxfish, not sleek, streamlined and sexy fish like a shark or marlin.

However, they had their reasons. And pretty decent reasons at that. There is conflicting science, but one group of researchers have found that boxfish are surprisingly streamlined and quick. They can swim at 6 body lengths per second and have a drag coefficient recorded between 0.06 to 0.2 (a flat faced box has 1.5).

The boxfish is incredibly stable from the keels shaped by the boxy carapace. These create vortices of water that intensify as they travel down the fish. When the fish points its nose up, the vortices are created at the top of the fish. When the nose points down, they form at the bottom. These vortices create lower pressure than the surrounding water, causing the tail end of the fish to raise or lower with the nose, keeping the fish level. The dorsal and anal fins can beat in perfect synchronicity to stabilize the fish more, and the tail and pectoral fins disrupt the vortices to turn 180 degrees with a near zero turn radius.

Given that a boxfish is also a much better shape for a car than say, a tuna, Mercedes took this all into account to create their Bionic car. Using the fluid dynamics behind the boxfishes awesome evolution, the car has it’s own tiny drag coefficient and lightweight maneuverability. Thus proving once again that marine life should never be underestimated. There’s a ton out there to inspire every part of our lives. From medicines to art and even vehicles that we use to get us to the oceans, nature is full of surprising and unintuitive muses to make our lives better, as long as we protect it to find them.

‘The surprising little Boxfish’ was written by Roya

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Roya Eshragh

Even as a little girl, I was obsessed with the oceans and wanted to become a marine biologist. So, I got into diving in 2011 as an aide for my Master’s research on cephalopod (squid, cuttlefish, octopus, etc) parasites. I completed my PADI Open Water course and continued with the CAUS Scientific Diver course in the cold cold waters around Vancouver BC. When time allowed, I would help with the Howe Sound Research Group of the Vancouver Aquarium monitoring the Sound. I’m sorry to say, but even after all that, I still haven’t quite come to love dry suit diving.

Once I moved to Madagascar as the Science Officer of a marine conservation NGO, I realized just how lovely diving in the tropics could be. There, I completed my DiveMaster and became addicted to daily diving. I had to find a way to continue! So I did my IDC in Bunaken, Indonesia, completing my MSDT course and learning the tricks of the trade on a few inaugural students.

Currently, I am a dive manager/reef ecologist in Sri Lanka and starting up a conservation and education program with my dive shop. Combining my love of the oceans with my love of science, I am thrilled to have found a way to bridge the two and teach others about this incredible ecosystem we still don’t know nearly enough about. There’s still lots more for me to learn, both about diving and about the marine world, and that is the beauty of it all!

PADI Specialty Instructor
CAUS Scientific Diver 1
Master of Science - Zoology

Dream Dive Locations:
Komodo, Indonesia
Silfra, Iceland
Wreck Diving, Lake Michigan

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