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Science

Deep-sea Camouflage Tactics Revealed 61

Posted by timothy
from the red-state-vs.-blue-state dept.
Honken writes "A recent study by scientists at Duke University has found that transparent deep-sea octopuses turn red when exposed to blue light similar to what predators emit, allowing them to hide using both transparency and by absorbing the wavelengths of the blueish light emitted by deep-sea predators. The Register quickly made the not-so-obvious connection to Kindles and squid video playback, whereas Discovery News reports on slightly more useful yet exotic applications, such as fishing nets that are invisible only to the species that it intends to catch."
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Deep-sea Camouflage Tactics Revealed

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  • ... my fish from refigerator?
  • by squidflakes (905524) on Monday November 14, 2011 @06:11PM (#38053154) Homepage

    These two species aren't the only squid or octopuses (or cuttlefish for that matter) that have amazing abilities in their skin.

    The Caribbean Reef Squid is able to flicker it's chromatophores and photophores on and off at greater than 120Hz, meaning that the squid are able to replicate the patterns of light and shadow against the sand and rock substrate caused by the waves in the water. It wasn't until we had some footage from The Discovery Channel taken with an HD high speed camera in an underwater housing that we realized that our original estimation of 30Hz for squid skin color change was way off. What we were seeing was the pattern as interpreted by our brain's somewhat limited image processing abilities.

    This really didn't come as a surprise as squid have optic lobes in their brains that dominate all other parts, and their optic nerves are absolutely massive, easily 100 times larger than the comparable neurons in mammals.

    Shallower and warmer water species of squid, octopus, and cuttlefish also have an ability that was touched on in the article, which is counter-shading their undersides to break up any silhouette they would create when seen from below. This is accomplished by photophores that emit light in similar frequency ranges as the sun after it passes through a few feet of water.

    Squid also use their skin's full-motion video ability for mating displays and communication, but I think I've already babbled on about squids enough.

    • by macraig (621737)

      ... I think I've already babbled on about squids enough.

      Nope, I don't think you have! More squid anecdotes, pls thx.

      • by squidflakes (905524) on Monday November 14, 2011 @06:58PM (#38053646) Homepage

        Oh.. well..

        The squid's brain is in five lobes, two lobes being oversized at attached via the single huge super-neuron to the corresponding eye. The other three lobes are typically used for running autonomous squid functions and don't light up much under MRI. The optic lobes however, are a bit like GPUs. The squid uses them for image processing but there are also hints of some higher order stuff going on. Not consciousness as we would recognize it, but something.

        Fun Cephalopod Fact!: The esophagus passes directly through the center of the brain. Cephalopod brains are radial, but not radially symmetric.

        Did you know that squid skin can be activated by electricity? The chromataphores are just sacks of pigment with muscles attached, and their displayed hue and saturation values are controlled by the expansion and contraction of these muscles. As the sack gets stretched, the pigment spreads out allowing more light to pass through. As the sack contracts, the concentration of the pigment rises and more light is blocked.

        Cephalopods also have irideophores which reflect only the blue/green (short) wavelengths of light. In reef squid, there is a higher number of these cells around the eyes giving that species their characteristic "eye-makeup" look. Strangely enough, when squid display eyeshadow patterns, it is usually the females and it is usually a mating related display showing at least mild interest. Male squid are capable of this display, but rarely show it. One thing we observed is that "sneaker males" which are beta-male squid that use subterfuge to mate with available females rather than alpha-squid strength and aggression displays, will often display eyeshadow and saddle patterns to convince alpha-males that they are, in fact, females. Then, when the alpha-male is busy being aggressive toward other male squid, the sneaker male will mate with the largest female they can find.

        Most squid that school are predominately matriarchal. The larger the female the more desirable she is as a mate. Particularly large female squid can have harems of a dozen males or more.

        Male squid that aren't good at mating, or are too pushy, or too aggressive, or aren't aggressive enough, sometimes get eaten immediately after the mating.

        I know far too much about squid sex.

        • by Forbman (794277)

          What about the Mimic Octopus?

          • by squidflakes (905524) on Monday November 14, 2011 @07:23PM (#38053898) Homepage

            It depends on what you're asking.

            Their camo is for defensive purposes only.* They get off kind of light as far as skin goes. They use kinesthetics to fool predators but tend to remain in a default black and white coloration. Most fish, and I would guess that enough animals that are predators of the mimic are color-blind. Most octopuses and squid are as well. Instead of color vision though their eyes filter the different polarizations of light and the guess is that they process the difference in polarization the same way we'd process a difference in color. So, instead of matching a background color, a mimic gets away with matching a background tone and then altering its body postures to produce a convincing enough silhouette.

            The black and dark colors are made by chromatophores, the white is make by leukophores.

            One interesting and thoroughly unscientific experiment I did involved altering the polarization of light my eyes were receiving, and then looking at squid and their predators while diving. I got a pair of welding goggles with replaceable lenses then ordered some circles of polarized glass. I got two lenses that only allowed vertical or horizontal light (depending on the angle of the channels to your eye) and glued them in to the goggles with some reference marks.

            With both lenses vertical I saw a lot of amazing stuff. The scales on fish were a lot less fuzzy and I could make out parts of the squid displays with more clarity. With both lenses horizontal, the scales on fish that normally looked silver would appear black at some angles. When I did one lens H and one lens V, I got a massive headache but my ability to pick out the details of fish and animal movement was increased by quite a bit. At the same time, the squid and the displays on their skin were brought in to sharp focus in some directions and very very confusing waviness in others.

            There was much mind blowing and Advil taking that day. However, that was exceptionally unscientific of me, and is presented as "hey, isn't that cool" only.

            *that we've observed in the wild. To my knowledge, no one has had observed mimic octopuses mating.

            • by Nursie (632944) on Monday November 14, 2011 @09:58PM (#38055132)

              Given how much you know about cephs, do you still eat calamari?

              Semi-serious ethical question. As a SCUBA diver that's interacted with Octopus on a few occasions, I find I don't really have an appetite for them any more.

              • by squidflakes (905524) on Monday November 14, 2011 @11:57PM (#38055718) Homepage

                I still eat squid, but I can't eat octopus for the reason you cite.

                I eat squid because everything eats squid, including other squid. Most of the calamari you get in restaurants is either California Market Squid or one of the more common species of Loligo, (which just had a taxonomy change and I can't remember the new genus) and they are, to use a scientific term, dumb as posts.

                That's how I rationalize it anyway.

                • by Nursie (632944)

                  LOL.

                  Yeah, roughly the same. Squid are pretty and interesting to look at, but I still eat them. Octopus, no, there's something about them...

                  I'm still on the fence with cuttles.

                  • by squidflakes (905524) on Tuesday November 15, 2011 @02:57AM (#38056650) Homepage

                    I won't eat cuttles. I raised too many generations, and they are at least as smart as dogs and trainable with Pavlovian methods. That moves them out of the food category in my mind.

                    Heck, I even trained a couple to ink on command. How can I eat my Super Cephalopod Inking Squad?

                    • Like I said, cuttles are smart enough to respond to Pavlovian conditioning. They also have a reflex to ink when they are in danger. Usually I would slap the surface of the water in the tank to get a few of them to ink, then offer them a juicy bit of shrimp or crab. Once a group of them started coming to the top of the tank when I would slap it, I stopped and would only feed them if they came up to the surface when I walked by. Cool story short, they got food for inking, then eventually food when I would tap

            • by LordPixie (780943)
              If you check back to this thread, I've got some random questions for you.

              I'm an avid recreational scuba diver, and have been fascinated by the few times I've actually come across a cephalopod underwater. But they're amazingly difficult for a novice to spot. I've even had difficulty pointing them out to other divers within an arm's length of them.

              Do you have any advice for actually seeing one of these buggers, when they're trying their best to look like a hunk of coral? Keeping an eye out for midden i
              • Really, the only thing that helps in ceph spotting is practice and experience. One of my buddies is an absolute natural at spotting octopuses and the midden is the best place to start. From there, watch for rock and coral formations that are slightly off in color from those around them or have a slight ripple. Octopus camouflage is great, but not perfect.

                The polarized lenses will help a bit if the animal is on a rock or sand. They can't affect the reflectivity of their skin and blocking out circular polariz

        • Re: (Score:3, Funny)

          by Anonymous Coward

          You're obviously japanese. Not to be racist; its just I've never seen tentacle porn aficionados of any other nationality.

          • by squidflakes (905524) on Monday November 14, 2011 @07:28PM (#38053958) Homepage

            Negative, I am American. I know very few tentacle porn researchers that are Japanese. Most of them tend to be Australian.

            • by macraig (621737)

              And thus we learn the true origin of the phrase "down under"....

    • by CODiNE (27417)

      With this and the other posts, you just pwned this article.

      Squid dude has his day.

    • by Sosetta (702368)

      I have now officially read my first article by a squid geek. Your post is so full of information that it qualifies as an article.

      Well done, sir, well done.

      • Thank you, thank you.

        The world of squid geekery is pretty specific. I can count on two hands the number of squid geeks I know, and they represent the bulk of biologists that specialize in cephs.

        If you've ever seen any of the squid or octopus shows on Discovery, then you've seen the Squid Geeks.

    • Good on you, having a life outside /. - whats it like???
  • It could deter predators by showing a distant shark approaching.

    And attract a mate by showing squid porn.
    • Only if you had species specific videos, and then you'd have to change them to respond to the squid porn you were getting in return. If you showed a lateral silver to a female, and she responded with a non-flicker saddle, you'd better flicker and black-silver-black before she oreo'ed and zebra'd.

      • Sweet mother of Jesus, that was some God-awful dirty talk. I have actually enjoyed reading every word you have typed so far. this is probably one of the more interesting articles I have read so far on /. I also like how virtually every time you have posted a comment, it has been modded to 5:informative/interesting. Keep up the good work! I hope there is another squid article soon so I can learn more about them.
        • Thanks!

          Yeah, that squid dirty talk can get down right nasty at times. I once watched a male approach the alpha-female of the group and flash lateral silver, followed by double oreo. She wasn't in the mood for any of his advances, so she flashed red and ate him.

  • I can't wait for a squid based color e-reader.
    • by Anonymous Coward

      It's called the Amazon Fire. Complete with stuttering transitions.

  • One thing you can count on SlashDot to be is just a few days behind The Register on tech or science articles.

    http://www.theregister.co.uk/2011/11/11/e_ink_display_squid/ [theregister.co.uk]

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