Deep-sea Camouflage Tactics Revealed

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."

Comments

So, my next Kindle can be assumed to steal...

[tr2sa]

... my fish from refigerator?

Squid are doing it for themselves

[squidflakes]

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.

Re:Squid are doing it for themselves

[macraig]

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

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

Re:Squid are doing it for themselves

[squidflakes]

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.

Re:Squid are doing it for themselves

[Anonymous Coward]

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

Re:Squid are doing it for themselves

[squidflakes]

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.

Re:Squid are doing it for themselves

[squidflakes]

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

Re:Squid are doing it for themselves

[macraig]

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

Re:Squid are doing it for themselves

[CODiNE]

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

Squid dude has his day.

Re:Squid are doing it for themselves

[Nursie]

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.

Re:Squid are doing it for themselves

[squidflakes]

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.

Re:Squid are doing it for themselves

[Sosetta]

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.

Re:Squid are doing it for themselves

[squidflakes]

YES! Finally! The one thing I can actually post intelligently about!

Feels good man.

Re:Squid are doing it for themselves

[squidflakes]

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?

Re:Squid are doing it for themselves

[squidflakes]

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 the side of the tank to "Shave and a Hair Cut."

One of the octopus geeks I know trained her octopus to take a little ride around the tank on her hand before feeding time.

Re:Squid are doing it for themselves

[squidflakes]

Ok, we're getting off in to a really wonky area. There is a reason that behavioral and social biology are called the soft sciences, and it is because you can't produce any standard numbers against which data can be compared. This is doubly true for intelligence. We get even wonkier because we're comparing mammals to mollusks. Sure, they both live in the ocean and can perform tasks that far exceed the abilities of other animals but on some very fundamental levels they might as well be from different planets.

I will say that I'm not really up on my whales and dolphins any more than I know about them as predators of cephalopods, but I will debate you on the intelligence question. As "smart" as they appear, squid and octopus are still mollusks. Their instincts and basic reflexes are no more complex than their cousins the snails, slugs, and bivalves. Yes, they have developed an intelligence that occasionally allows them to react in ways that are counter to instinct, but they don't do it often or with consistency.

Octopuses don't plan. They can remember, especially if they are using spacial memory, but they can't think ahead. They really can't anticipate more than a few moments in advance, which is on par with dogs, parrots, and infant humans.

Dolphins, on the other hand, are constantly displaying this ability. One of the most obvious uses is when a pod of dolphins traps schools of feeder fish by blowing bubbles under then, and then swimming around the school at high speed in tighter and tighter circles. The dolphins are able to anticipate the motions of the school of fish and adjust their motions accordingly.

Having said that, if you can post some links to the studies you're reading, then please do so! Please prove me wrong! I'd be happy to be able to wave those in the face of the cetacean researchers I know.

Oh, and to keep babbling, social intelligence is a lot more important than you seem to think. I never said that social skills were required for intelligence, as that would elevate ants and bees instinctual process to something we'd call intelligence, which isn't the case. What I said was that dolphins have much more social intelligence than octopuses and that is a sign of higher thinking. Troupes, as opposed to packs, hives, or flocks, are at-will structures. An ant doesn't make the choice to join the hive, and a dove doesn't select one flock over another. However, dolphins and whales do join pods outside of their family groups, and chimps engage in all sorts of social group creation. The memory and abstract thinking required to approach and join another troupe (be it a dolphin pod, gorilla pack, or clique of humans) is absolutely massive. You have to build a mental map of an ever changing social structure, understand the hierarchy, understand your own place in that hierarchy, and learn the values, taboos, and symbols that are used to communicate the troupe structure.

That is a load of work that you don't even notice that you're doing, and it is probably the reason that human brains are so utterly gigantic when taken in proportion to our body mass.

So why is it important? In our case, it is only through social intelligence that we manage to survive at all. Humans, and our close ancestors are sacks of hairy meat with very little in the way of natural defenses. We have no claws, blunt teeth, low strength, soft skins, no camouflage abilities, terrible eye-sight, poor hearing, and limited mobility when compared with the rest of the animal kingdom. Individually, we're pretty helpless, even when confronted with a non-apex predator. Hell, a medium sized domestic dog CAN kill you. Together though, we start having a multiplicative effect on one another. We can plan, organize, communicate, and anticipate. As the number of humans grows, the social structures we build can last much longer than an individual member of the group. Through those structures we pass on knowledge and experience, which substitute nicely for instinct. Through these structures we have been able to perpetuate ideas that have led to things like the Great Pyramid and the moon landings. None of that would have been possible without social intelligence.

Re:Squid are doing it for themselves

[squidflakes]

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 polarization will help. I don't think IR is going to help much because light in that wavelength transmits so poorly through water. I don't know if you could get a hold of one, but lasers and LED lights that are heavy in the blue/green spectrum will make the iridophores much more apparent. The LEDs tend to work better because you have a wider frequency band to work with.

Go slow. I was once floating in about 5 feet of water, just resting and letting the light current push me toward the spot on the beach where I had left my stuff. Suddenly, I saw two eyes pop up out of the rocks on a stalk. After a few moments, I saw that the stalk was attached to an octopus and it slowly crept out of the hole, over some other rocks, around a fan coral, and in to another hole that was an obvious octopus den. Octopuses watch for sudden motion, so the more like a log or cloud shadow you look, the easier time you'll have.

Finally, familiarity. When I was studying squid behavior in the field, the squid got used to the team floating above them and were much more apt to act naturally. The squadron we were watching on that trip got very used to us and wouldn't even scatter when we moved or splashed around. The alpha-female of the group, Trinity, would even pull interested males toward me and see how close they would get before freaking out. (flash red black) The closer they would come, the more likely it was she would mate with them.

This led to much squid sex less than a foot from my face.

Re:This is great!

[Anonymous Coward]

I assumed the point was that free enterprise cephalopods are able to make better pigments and employ better camouflage tactics then their larger, slower, and dumber government bureaucratic cousins.

Re:So if it could play video

[squidflakes]

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.

Re:SlashDot - just a few days behind The Register

[squidflakes]

My pleasure. Just spreading the word about these wonderful and woefully underestimated animals.

Some of the researchers I've worked with have taught their octopuses to play with Legos. How can you not be fascinated by an animal that plays with Legos?

Re:So if it could play video

[squidflakes]

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.