A Bleedin' Octopus!

Discussion in 'Physiology and Biology' started by Level_Head, Jun 11, 2010.

  1. Level_Head

    Level_Head Vampyroteuthis Registered

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    My apologies, folks from UK and Australia -- I don't mean it that way.

    In videos that I've seen, octopus blood is rarely visible, and when it is it's not guaranteed to be distinct from an inking response to fear/injury. Even in videos showing cutting of live animals (ugh!), I understand that essentially no bleeding is visible. Is this an artifact of our poor vision?

    Octopuses have apparently around 4% to 6% blood by body mass, and according to the paper below they have the ability to recover quickly from a loss of 40% or so of their blood using fluid filtered from their digestive tract. (Apparently, all of their water intake comes from this source; tie those ducts off and they quickly die of thirst.)

    So -- is octopus blood ever visible in the water? Do body injuries have the "instant seal" effect that a lost arm has? Is that effect different by species?

    This was the paper that talks about blood loss:
    "FLUID UPTAKE AND THE MAINTENANCE OF BLOOD
    VOLUME IN OCTOPUS"
    http://jeb.biologists.org/cgi/reprint/175/1/211.pdf

    A question that occurs to me: If they never lose blood, how did they evolve to be so good at replacing it?

    Also, would blood in the water be visible to octopus eyes, with their much greater sensitivity to low light and polarization?

    And how about the octopus's sense of smell? Can he smell the blood of another octopus?
     
  2. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    From my understanding, all of the marine animals get their freshwater from what they eat (ie not an oddity of the cephalopods). I have tried multiple times to get some of our biology folks to explain why an octopus does not dehydrate with it starts fasting. GPO's are believed to fast for more than six months when they incubate their eggs. For those that will eat, it would seem freshwater crustaceans might be a good idea at this end point of their lives.
     
  3. Level_Head

    Level_Head Vampyroteuthis Registered

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    I think there's a distinction to be made between "from what they eat" and "from seawater passing through their digestive tract."

    Octopuses, apparently, produce about 9% to 12% of their body masses or thereabouts in urine every day. If the glands involved in that filtration are "ligated" (ducts closed) the animal dehydrates very quickly. But this is true whether they eat or not, it seems from the literature.

    So, even a fasting, brooding mother is still filtering seawater from the digestive tract into pure water for the body -- or she's stopped 99% of urine and other waste production. I can see a great reduction of solid wastes, but metabolic wastes would still be happening I'd expect; she still has a metabolism.

    I don't know if this gut-water filtration is more efficient or less when accompanied by eating -- it may not be much affected at all.
     
  4. Level_Head

    Level_Head Vampyroteuthis Registered

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    An update on octopus liquid intake: You know the old expression, "to burn a candle at both ends"? (It comes from Edna St. Millay's poem at the beginning of "A Few Figs from Thistles":
    This poetry reminded me of the octopus's short but remarkable life -- but there is another sort of peculiar connection.

    The octopus apparently "drinks" from both ends. I was originally put onto this notion when I noted that in studies of blood and urine volume, they had to tie off the digestive tract at both ends. This paper mentions that, too, but also mentions the reason: "Rectal pumping":
    http://jeb.biologists.org/cgi/content/abstract/145/1/215
    The use of tubes proves that taking in water from the ocean does not require eating -- but we'd figured that out, I think.

    Back to the topic:
    I'm still hoping to hear from anyone who has ever seen octopus blood -- or knows definitively whether it's visible to humans.
     

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