Archerfish : Bullseye

Archerfish (Toxotes spp.) are – how to put this politely? – small, kind of unremarkable- and certainly inoffensive-looking fish of tropical Asia. So why are they so (relatively) famous? Famous enough that the US Navy got into the habit of naming submarines after them. There can’t be that many people who don’t know exactly what makes archerfish special – the clue’s in the name, after all.

The trick these fish are pulling off looks kind of simple at first glance. But, as with everything in Nature, there’s more going on than meets the eye. Time to incorporate some (very gentle, very simple) physics into the Wild Episode, and enjoy the modest wonder that is the archerfish’s water-based machine gun …


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Hit the View Post button for film of the awesomely cool coelacanth (really quite soothing to watch, I promise!), and links to much more info on this legendary fish …

Before we get to Nature, check out a man-made wonder:

The USS Archerfish (the first of that name) holds the record for sinking the biggest vessel ever sunk by a submarine: the Japanese aircraft carrier Shinano. Here’s the Archerfish herself:

(not the subject of this episode!)

But here’s the original and, of course, the best doing what makes it famous:

(definitely the subject of this episode!)

Not the greatest illustration, that – although cool to see not a continuous jet of water but a chain of droplets (if you’ve listened to the episode, you’ll know why!). Here’s a slightly better look at the archerfish:

Fair to call it unremarkable, I think. But then, of course, it goes and does its thing, and all of a sudden it looks a whole lot more remarkable:

Learning by watching? Maybe. But how did the first archerfish to break the water barrier figure out how to do it? Trial and error, presumably, starting from the base provided by the pre-existing ability to use water jets underwater:

For the technical details on how the archerfish’s jet actually works, this paper from Plos One:

Vailati, Zinnato, Cerbino How Archer Fish Achieve a Powerful Impact: Hydrodynamic Instability of a Pulsed Jet in Toxotes jaculatrix. It’s quite a cool, but slightly technical, study. If, however, like me you find things easier to grasp if you can see them, scroll down to near the bottom of the paper – in Supporting Information – and there’s an awesome, very brief video showing precisely what they’re talking about. You can clearly see the jet compressing at it rises: the back end catching up with the front end. Awesome.

Further archerfish reading:

Spit Decision: How Archerfish Decide at wired.com

Archerfish Actively Control the Hydrodynamics of Their Jets in Current Biology. (What Archerfish get up to with their jets is actually even more complicated and ‘clever’ than I get into in the podcast!).

PDF link! : Archerfish use their shooting technique to produce adaptive underwater jets in Journal of Experimental Biology Advance online articles. (They do the same things underwater as above water!).

Music

Opening & Closing Themes: Running Waters and Acoustic Meditation by Audionautix (Jason Shaw), from audionautix.com.

Revenge by Daniel Birch.

Ecclesia by Ambienteer.

Underwater by Meydän.

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