Fish armor and Friday Harbor: Investigating the tradeoffs of heavy body armor in poachers

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A CT image of the Northern Spearnose Poacher

It turns out that life as a member of the food-chain is tough, and while humans don’t really need to worry about being eaten alive on their way to the grocery store, every other animal on the planet has to develop traits that ensure they don’t become lunch.

Marine animals often use camouflage, speed and maneuverability, or safety in numbers to survive the warzone in the water. These traits, however, come with tradeoffs.

“Every trait that a species evolves comes with some kind of cost,”  Sebastian Kruppert, a postdoctoral researcher studying poacher fish body armor at Friday Harbor Labs (FHL), said. “If you are heavily armored, that will maybe restrict your maneuverability or come with the cost of not being as maneuverable or as fast as other species that are the same size or a similar shape, for example.” 

Kruppert was first attracted to studying these fish after speaking with professor Adam Summers. Summers, who advised Pixar about fish movement for the movies “Finding Nemo” and “Finding Dory” and launched a movement to “#ScanAllFish,” has a lab at FHL with all the tech necessary to make a biomechanics postdoc researcher like Kruppert travel to the labs from Germany. 

“FHL is a playground for science,” Kruppert said, “Adam has a fully equipped lab with a scanning electron microscope, different light microscopy techniques, a CT scanner, and that's all the imaging side.”

In addition to the imaging tools, Summers’ lab also has a 3D printing facility that can print the morphology scans, allowing Kruppert to more closely and less invasively study poacher body armor and any potential tradeoffs that might come with the development of the thick, rigid structures.

Summers’ supervision and the ample resources from his lab at FHL combined provide all the tools needed to take a closer look at these tradeoffs that specific morphologies can give functionalities of interest, Kruppert explained. In simpler terms, Kruppert has all the tools to test how the big, spiny armor might influence speed or defensiveness, for example.

Poachers are relatively young compared to ancient fish species in evolutionary terms, which makes these fish even more intriguing for researchers — especially because the origin of this body armor is still not well known.

“We're not sure if they're actual scales, or if they have the exact same origin as the usual fish scale,” Kruppert said. “It's double skeleton and has a really big and thick structure.”

Kruppert found that despite these fish’s lack of swim bladders, living on the seafloor, and having heavy body armor, they still seem to be pretty maneuverable and fast so far. Maneuverability, though, is just one potential cost that could come from developing such heavy defensive body armor, and some of these poachers are more heavily armored than others.

So far, Kruppert has tested the level of body armor for 27 species of poachers and found that on average, these fishes have invested five times more mineral into their body armor than into their internal skeleton. 

Of the poacher fishes tested, some had as much as 10 times as much mineral invested into the armor compared to the skeleton. Some of these more heavily armored species that have yet to be tested might demonstrate certain maneuverability tradeoffs.

Maneuverability tradeoffs aside, Kruppert is also interested in other ways that this armor can impact predator-prey interactions, including how this armor can act defensively or offensively.

These scales could be used to defend against different types of predator attacks. Perhaps they are more effective at defending against crushing jaws, or piercing spines. Or maybe the converging plates that form spines are used for offensive purposes to attack other critters.

In addition to understanding more about the tradeoffs, benefits, or costs of heavy body armor,  Kruppert said there might also be lessons to learn from these poachers that are applicable to the engineering world.

“If we learn how these poacher scales overlap and interlock, and if we are able to reproduce that then we might be able to build a coat for things that keep them somewhat flexible while also protected,” Kruppert said. “Like protective cover for flexible pipes or cords.”

Reach contributing writer Dave Berndtson at Twitter: @DHCBerndtson

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