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The things you learn, eh?

Deep-sea adaptations tended to be less visibly obvious, he said. “One of the reason [snailfish] are so successful is they don’t have swim bladders. Trying to maintain a gas cavity is very difficult at high pressure.”

19 thoughts on “The things you learn, eh?”

  1. Trying to maintain a gas cavity is very difficult at high pressure.

    So they don’t fart either?

  2. “Very difficult” is an understatement.. It’s lethal to the fish.
    At those pressures even the heat generated from their muscles if they have to rush for something can have the gas in it expand to such an extent that they’d bob up like a cork and then explode…
    Which is why they rely on those osmolytes to control their density.

  3. The Meissen Bison

    The accompanying image is worth a look because the snailfish and Capt. Potato look weirdly similar.

    AtC – Grikath can probably answer your question but did you spot the news item (2nd Apr) that cattle are now to be given additives in their ration to curb flatulence? Why pick on cows when they’re given such a rotten example by our leaders?

    (Come to think of it maybe that story explains the coronation boycott)

  4. @Grikath
    That’s odd. I was presuming it was the difficulty of getting gasses out of solution with water at pressure. Demonstrated by it’s only when you take the top off a bottle of pop it fizzes. To get free gas, there has to be sufficient dissolved in the water to saturate at that pressure.
    From that, it’s hard to understand the problem you’re talking about. The gasses & water are at the same pressure. The gas exchange through the gills is less efficient? One would think they’d evolve greater gill area.

  5. @BiS, ah yes.. But that’s under pressures we work at…

    The problem here, as with all things Thermodynamic is with that evil Delta in the equations, and one of the factors ( pressure) in the equations being really big. ( you can’t imagine how big, etc..)
    With pressure being so high, even the smallest changes in anything else gives huge differences in the energies and gradients involved, which makes things…tricky..
    And that’s for ideal gases…

    The biggest problem here is CO2, which first of all does not behave like an ideal gas in solution** , but reacts with water to become carboxylic acid in solution in an equilibrium reaction, making it very easy to supersaturate water with CO2..
    And as your example of the fizzy bottle shows, that equilibrium is… very temperamental.
    So temperamental that our haemoglobin is crucial in stopping our blood turning into fizzy soda when the weather changes rapidly… ( yes.. it evolved to do that well before oxygen became a Thing…)

    Plugging a pressure of 800+ atmosphere into those equations, you get a result that’s almost a factor 1000 more temperamental…
    Like with relativity there’s non-linear behaviour when factors get that large, so roughly “only” a factor 100, but still.. Verrah Tricksy…

    Which is why deep-sea life actually doesn’t allow any free gas to exist, but tightly binds it to proteins using the same sugar complexes that make up our DNA, which have a way more permissive equilibrium so things get less Tricksy.

    Which also answers the question why deep sea fish don’t fart, ever…

    And CO2 is a problem deep down, because all life there is basically anaerobic, so it produces a lot of it. And those osmolytes actually play a role in binding it as well, besides creating the osmotic pressure needed to survive at that depth.
    When it comes to fish, they use their gills to slowly regenerate their “oxygen debt” using the minute amounts present at those depths. But even that is a minor fraction of what they actually need.
    So quite often you see symbiotic relationships with anaerobic bacteria, sometimes even chemotrophs, who love all that CO2 and use it for their own internal processes.
    And the most common place where those symbiotic bacteria live is in the gills.
    It’s a perfect example of evolution where an organic structure keeps the same function ( “gas” exchange ) using a completely different paradigm.

    Like Pratchett’s Draco Vulgaris, they adapted to cope with living on the Edge.
    And I half-wonder, with all the actual-science sir PTerry worked into his scribblings, whether or not he read up on or was explained stuff like this when he thought them up.

    **Only the noble gases behave anything like ideal gases in solution with water.
    Water is nasty. If it were invented today it’d be banned immediately and the peeps that invented it strung up for coming up with something that dangerous for good measure.

  6. I think (relying on vaguely remembered gas laws) is that the saturation level decreases with increasing temperature. So being fully saturated at, say, 1500atm and 0C is shaken coke bottle fizz at 1500atm and 1C.

    Personally I’m sceptical of the ‘pop like fizz’ theory.

  7. A linked article in the Graun begins:

    I sometimes describe anglerfish as looking like a satanic potato,” says James Maclaine…

    Which somehow seems appropriate for his spudiness

  8. @Andrew again, the comnparison with a shaken coke bottle is, of course, an easily visualised exaggeration.

    You need only tiny bubbles for emboly… See also caisson disease and emphysemia-induced strokes..
    A lot harder to convince people how fast things can go downhill with even the tiniest of bubbles..

    Ah well.. I avoided Math.. And got to work in H2G2 and sir PTerry.. 😛

  9. SBML, the formal name is actually Oxydane. Endless amounts of fun to be had with that one… 😉

  10. Hmm, so if we force out kids to drink oxonium will they do PPE at Oxford – or, of course, fail it?

  11. Thx Grikath. I’ve done a few dives in my time so am aware of the weakness of the analogy! Thx for the detail though. V interesting.

  12. @Tim, Not specifically, but certain forms of Oxonium are known to inhibit common sense sufficiently to engender… Bad Life Choices.. Kids and PPE studies are notorious results of that..

    @BiS You surely jest? Everybody knows that the surefire way to fail PPE is to fail to replicate the lecturer’s Opinion at exams.

  13. Angler fish are scary bastards.
    Some species can grow up to 1m!
    And their jaws can distend allowing them to swallow prey twice their size… So a human adult then.

    If they ever adapt to lower pressures and grow legs… Nightmare fuel.

  14. BniC, “Iä! Iä! Cthulhu fhtagn! Ph’nglui mglw’nfah Cthulhu R’lyeh wgah’nagl fhtagn!” 😉

  15. Grikath @ 5.52
    Sorry, pendant alert: (or a case of sausage fingers…) It’s Oxidane. I googled Oxydane (sic) and got adverts for some supplement “for the horses we love”.

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