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"Argonaut" Octopus Sucks Air Into Shell As Ballast

Posted by timothy on from the 8-legs-good dept.

audiovideodisco writes "Even among octopuses, the Argonaut must be one of the coolest. It gets its nickname — 'paper nautilus' — from the fragile shell the female assembles around herself after mating with the tiny male (whose tentacle/penis breaks off and remains in the female). For millennia, people have wondered what the shell was for; Aristotle thought the octopus used it as a boat and its tentacles as oars and sails. Now scientists who managed to study Argonauts in the wild confirm a different hypothesis: that the octopus sucks air into its shell and uses it for ballast as it weaves its way through the ocean like a tiny submarine. The researchers' beautiful video and photographs show just how the Argonaut pulls off this trick. The regular (non-paper) nautilus also uses its shell for ballast, but the distant relationship between it and all octopuses suggests this is a case of convergent evolution."

7 of 72 comments (clear)

  1. That's not ballast. by jcr · · Score: 5, Informative

    Ballast is weight that counteracts buoyancy. By introducing air into its shell, the animal is adding buoyancy.

    -jcr

    --
    The only title of honor that a tyrant can grant is "Enemy of the State."
    1. Re:That's not ballast. by Daniel_Staal · · Score: 5, Informative

      As the pressure increases with depth, the volume of the air will decrease as it is squeezed into a smaller space. Buoyancy is determined by density, which is mass per unit volume. Mass is staying the same, but volume is decreasing.

      Above a certain depth, they will be be positively buoyant, and rise. Below that depth, they will be negatively buoyant, and sink. They gather enough air to be neutral at a certain depth, and stay there. The more air they gather the lower that depth is. If they can't get deep enough, they will tend to rise back to the surface (unless they vent air).

      The article is right.

      --
      'Sensible' is a curse word.
  2. Neato (: by DarkKnightRadick · · Score: 3, Interesting

    And for it's next trick, the octopus will change its color!

    Oh wait, some already do that.

    --
    "There is a way that seems right to a man, but its end is the way of death." Proverbs 16:25 (NKJV)
  3. Ubuntu? by Saeed+al-Sahaf · · Score: 5, Funny

    "Argonaut Octopus" ... That's the new Ubuntu release, right?

    --
    "Who are in control, they are not in control of anything - they don't even control themselves!" - Glen Beck
  4. Debated for millenia? by pdxp · · Score: 3, Insightful
    From TFA (emphasis mine):

    Finn and Norman filmed and photographed live animals in the act of trapping their air bubbles, solving a mystery that has been debated for millennia.

    Somehow I am starting to think that exaggeration in the media goes too far sometimes....

    1. Re:Debated for millenia? by ivandavidoff · · Score: 4, Informative

      FTFA: No less a thinker than Aristotle put forward a hypothesis.

      That was about 2.35 millenniums ago.

  5. Re:Mating Rituals by somersault · · Score: 4, Funny

    The arm doubled as a penis, snapped off during sex and stays inside the female’s body.

    Yep, this has happened to me quite a few times. I'm just glad these things grow back!

    --
    which is totally what she said