ibuyufo - May 16, 2011

Maybe I'm blind but where exactly is this cuttlefish?

yOnsa - May 16, 2011

lower right pie section of the circle, i think. see those bumps that aren't as random as the rocks?

ibuyufo - May 16, 2011

Thanks! Gotta hand it to the cuttlefish!

Eikka - May 16, 2011

Considering that the fish live in the same environment with the same type of rocks and sand for eons, I don't think it's far fetched that they simply take a guess based on what surface they happen to land on.

Life quickly weeds out those who guess wrong.

hush1 - May 16, 2011

...the way that color is quantified in sensory (perceptions)studies of camouflage and signaling in the natural world.


Close enough. Have fun rediscovering centuries-ago-answered questions. Just don't get caught rehashing the past as something new. You might lose cover.

DavidMcC - May 17, 2011

This is a very interesting conundrum. I wonder whether cuttlefish (and octopuses/octopodes) express visual opsins in patches of their skin that may (directly or indirectly) connect to their chromatophores. I can't think of any other way they could do this camourflage trick. Such additional opsins would not be expressed in their eyes, but could still be identified in their genome. I do not know of any research results on this.
PS, I thought it was in the bottom left, not the right. Could be wrong though. :)

DavidMcC - May 17, 2011

... It would make sense to take the colour vision out of the imaging eye if all that is required is the general colour of the background. The reason is that there would otherwise be a significant price to pay in terms of acuity, due to the limited space available in the retina for the extra colour receptors.

DavidMcC - May 17, 2011

Hush1, I take it that you have references from several centuries ago on the biology of cephalopod camourflage!

antialias - May 17, 2011

The interesting thought in this article is that it's not the camouflaged animals' vision that matters but the predators' vision which must be fooled. However, the prey must still know which types of background will be efficient camouflage.

It seems to me that this would force a convergent evolution of the eyes of predator and prey (at least of the color spectrum they are sensitive to). Any maladatptaion would lead to a wrong choice of camouflage and therefore to sudden death.

DavidMcC - May 17, 2011

Not necessarily, antialias. The best strategy when there are diverse predators (probably with varying vision) is to simply match the skin colour pattern to the background over as wide a range of wavelengths as possible.
____
On the question of control of chromatophores, there are at least three modes that cuttlefish have: camourflage, courtship and other signalling. I suspect that this means that the only conscious control the animal has over the chromatophores is which mode to be in.

PS. I've just seen it in the picture! Right across the bottom.

DavidMcC - May 17, 2011

For the camourflage to work, there would also have to be input fom the creature's eyes, just to get the texture correct (minus colour), combined with colour sensing from other skin organs than the eyes.

DavidMcC - May 17, 2011

It seems that the opsins expressed in the skin of cuttlefish have already been found:
http://rsbl.royal...223.full
"Evidence for distributed light sensing in the skin of cuttlefish, Sepia officinalis"
So, conundrum solved (albeit only last year)!

hush1 - May 17, 2011

The article is somewhat misleading. How do you represent a colorless world when your only perspective (senses or perceptions) are that of a cuttlefish? The spectral discrimination has been eliminated. So a background with color needs no further consideration. The interactions or exchange of information between cuttlefish and environment does not include spectral discrimination. What are the signal representations of recognition and operation (of living) in a colorless world? The organism is able to perform without spectral discrimination. Yet the authors opt for this.

I have century-old references to signal representation in a colorless world. Do those signal representations (energy distributions) have a biological/chemical expression in cuttlefish? Assigning 'purpose' to expression can be done at anytime during research.

People born blind and color blind have representations in their mind of what color is. A different representation from ours. What is 'camouflage' to them?

DavidMcC - May 18, 2011

Hush1, check the link I supplied above. It shows that cuttlefish do actually sense the colour of their environment, but not using their eyes. This is because space on the retina is too valuable to waste on something that can be done in the skin. It doesn't give them colour vision, but it does enable them to use colur to camourflage themselves effectively.
I doubt that this had been fully understood a century ago.

DavidMcC - May 18, 2011

Sorry, repeat comment. Due to a technical problem with the brouser or site.

DavidMcC - May 18, 2011

Hush1, on the subject of "signal representations", I doubt that the ability to imagine colour would help a cuttlefish actually match its colour to its surroundings.

hush1 - May 18, 2011

Hush1, on the subject of "signal representations", I doubt that the ability to imagine colour would help a cuttlefish actually match its colour to its surroundings.


I agree. I share your doubt.
Obviously, the signals have a "representation" and form that differs from the point of origin where the signal originates.
(Maybe the 'depot' for this signal/information is the brain).
Whatever that brain "representation" is, the "spectral" discrimination is not "spectral" for the cuttle fish.

To end speculation, simple put cuttle fish in an artificial "black and white" environment and watch what happens.
The smallest and cheapest test to big research.

DavidMcC - May 19, 2011

Hush1, speculation on this subject has already been ended by the work of Mathger et al. (linked above) that showed that cuttlefish can detect the colour of their surroundings through visual opsins in their skin, as I mentioned before.

hush1 - May 19, 2011

The work of Mathger et al. ends all speculation on this subject!

(!) <--(eyebrows raise, eyes widen, jaw drops in dismay)

DavidMcC - May 20, 2011

That's right, hush1. There is absolutely no need to propose that random guessing is required when the cuttlefish can detect colour in its surroundings, even if it isn't actually seeing the colour. The chromatophores that determine the colour pattern in its skin can be adjusted using the non-eyesight colour information.

DavidMcC - May 20, 2011

... It seems that there was no room in its retina for all the extra photoreceptors, which would degrade its visual acuity unless its eyes got a lot bigger (which would be expensive). Perhaps it doesn't use them for hunting, only for predator avoidance by an unconscious camourflaging process.

hush1 - May 20, 2011

Put the fish in a black and white environment. Regardless of God's absolute...oops wrong thread,... regardless of the work of Mathger et al. that ends all speculation. Nothing is absolute.

And this fast, cheap, simple, experiment can be just another feather in the cap/hat of additional data fortifying the researchers conclusions. 100% confidence researchers welcome anything strengthening an original hypothesis/theory - the more additional data confirms, the more merrier the researchers. Nothing can "threaten" a confidence level of 100 percent. So why even the need for additional experimentation to support a successful existing theory?

That was stated already. Nothing is absolute. There are as many rationalizations for not questioning the "end of all speculation" as there are the number of questions, questioning the exist of God.

When I last checked, that was a lot questioning.
And we all know God needs no data or support.

DavidMcC - May 23, 2011

Hush, stop twisting my words about "100% confidence" (your words, not mine) to cover for a falsfified hypothesis. There is no way that the superb camourflage colouring that cuttlefish (and some species of octopus) consistently achieve within seconds is done without using the colour receptors in their skin.
Basically, it's absurd to portray a scientific conclusion as being religion-based, as you are doing, on the basis of a phrase I used.

DavidMcC - May 23, 2011

To put it another way, hush, it is bad science to cling to a falsified hypothesis that relied on lack of information at the time.

DavidMcC - May 23, 2011

BTW, hush, I'm an atheist!

hush1 - May 23, 2011

There are as many rationalizations for not questioning the "end of all speculation" as there are excuses for not questioning work at all.

Here's one more:
"There is NO WAY ... in their skin."

You missed the point referencing God completely. The emphasis is on the RATIONALIZATIONS anyone uses to defend conclusions.

Whether those conclusions are reached through scientific method or religion is completely irrelevant to the point at hand - namely, your rationalizations.

"...NO WAY..." is a rationalization. A completely unscientific, unfounded, illogical expression to avoid scientific inquiry and legitimate question or doubt.

Alright. I'll state this differently:
Nothing is absolute. There are as many rationalizations for a scientist's 'fact' as there are falsehoods. Every one of those rationalizations make "sense" for a scientist as long as those rationalization support the scientist's fact and not the falsehood.

DavidMcC - May 23, 2011

Hush, once again, you are turning truth on its head. There is, indeed, no way that any organism can respond reliably to its environment without information about that environment.

You, presumably, think that the late Paul the octopus actually had a supernatural ability to predict the result of football matches!

DavidMcC - May 23, 2011

... Of course, I am not arguing that Paul the octopus was using his senses to predict football match results, only that, because he could not know anything about football matches, that he could not have been involved in any overcoming of heavy odds against success that might have occurred.

hush1 - May 23, 2011

If you want to label scientific conclusions to experimentation "truth", by all means, do so.

"There is, indeed, no way that any organism can respond reliably to its environment without information about that environment."

We, humans, respond reliably to death. There is no information we know of, about that state of the environment.

DavidMcC - May 24, 2011

Hush1, I'm afraid "death" isn't an object in the environment, so your argument is nonsense - we do not "respond to death", we simply die. Although this ridiculous thread seems to go on forever, largely because of your obsession with a bit of century-old woo science.
By "truth", I mean an observable fact.

DavidMcC - May 24, 2011

...And yet another point, hush1. Your use of the word "rationalization" is what actually applies to your pet woo theory, because the word implies bending logic to make what does not make sense SEEM to make sense. The Mathger paper allows us to make sense of observations, your woo forces rationalizations (ie nonsense, such as "they imagine the colours").

hush1 - May 24, 2011

You are sadly mistaken. The outcome of dieing is death. A part of Nature. If you do not view this as a part of Nature, you are not a scientist. Which you have supply amply wording to support. If you are anything, being a scientist or conducting science is not what you do.

"death" isn't an object in the environment


Enlighten us with your death-defying semantics of what death is.
You have wasted everyone's time.

Anyone can see this "fact".
It is "observable" right here.
I see no point to further engage in your nonsense.
Feel free to "woo" others with your "logic". (Wave your wand)

Let us know if your work even does ever turn towards science.

DavidMcC - May 25, 2011

This thread is getting silly. Hush1, the most naive person on the site, who understands nothing about science, is pretending he's the expert and I'm just a fool.

Perhaps physorg staff should indicate a final score, by actually rating the posts?

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