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

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

[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

[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

[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

[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?