I go to the Como Zoo & Conservatory (http://www.comozooconservatory.org) every Sunday morning that I have free. There is always something new to see. For example, I had always hoped to see the archerfish, housed in a tank in the marine house (with the penguins and puffins and seahorses!), use their amazing shooting ability to hunt for bugs.
And one morning a few Sundays back, I got my wish. The zoo staff member feeding the fish was placing grasshoppers (I think) on the rocks a couple of feet higher than the fish in the tank, and the fish were “spitting” jets of water at them, knocking them into the water to eat. It was spectacular. And the family near me watching the spectacle was not sure that they were really seeing what they were seeing. “What’s going on?! Are they jumping up so fast we can’t even see them?!”
It’s one of those awkward moments, right? You know something, but you don’t want to look smart-alecky. But I was so excited I couldn’t contain myself, and I explained a little about how these fish hunt, how they have special eyes, brains, and mouths that allow them to do this amazing thing. And then I sort of caught myself and said, “Sorry to go off there…these are just some of my favorite animals.” Fortunately, the mom said, “No, no…I’m really glad you did! That is fascinating.”
So it’s not always a bad thing to show off a little of what you learn, outside the classroom, I guess.
Coincidentally, a study just a week or two later in the Cell Press journal Current Biology on September 4 said that archerfish are even more skilled than had been realized. Using water as they do includes them in the fairly exclusive club of tool-using animals (although that club seems to grow every year, doesn’t it?). What makes it tool use—and not JUST tool use, but SKILLFUL tool use—is the way the fish change the hydrodynamic properties of the jet of water from their mouths.
One of the scientists who conducted the archerfish research said that this high level of accuracy probably evolved because where the fish are located, “there is very little to actually shoot at, so it’s important for the fish to be efficient.”
Paper authors Schuster and Gerullis trained some archerfish to hit targets from 20 to 60 centimeters from a specific location, and measured the water jet variables produced. This led to the discovery that archerfish are able to adjust the jet, in ways that compare with how human throw projectiles at targets. Schuster said that this ability requires “precise time control of movement.”
The scientists speculated that what they have learned about water jet control from the fish might find application for human products, including in medicine.
Archerfish, because of their unique hunting adaptation, have sometimes been used as an example of an organism that could not have evolved by Darwinian means. The number of “moving parts”—in the mouth, brain, and eyes—needed to produce such an amazing adaptation really is dizzying. In that way it reminds me of the mimic octopus, which has such a near-perfect ability to imitate its surroundings, camouflaging itself into almost any background by means of color, pattern, and even texture, that it seems more like magic than biology.
How great for science that such challenging puzzles abound! Using the tools of science in the natural world, what discoveries might we make in our efforts to answer such puzzles that contribute to our understanding of the natural world, and maybe make our lives better? Anyone who had the mad skillz of a mimic octopus or an archerfish would be a superhero to rival Mystique or Hawkeye.
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