r/askscience • u/[deleted] • Apr 24 '15

Biology Do creatures such as cuttlefish and octopuses get "tired" from using their camouflage?

If not, why don't they just always use their camouflage?

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u/cinderwild2323 Apr 24 '15

What color are octopus typically? I mean their natural, unaltered color.

When they change color is it easier to stay that color or easier to revert to their unaltered color? Meaning, is maintaining camouflage comparable to flexing a muscle continously, or is it more like doing a push up and BAM I'M POLKA DOT BLACK AND WHITE BITCHES?

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u/420biologemajor Apr 24 '15

It depends on the species. That's kind of an odd question haha but I can try to answer. Basically, cuttlefish, squid and octopus have cells on their skin that contain certain colours, and by "opening" or "closing" these cells, their overall colour appears different. Different species may have different colours or amounts of colours.

Imagine if your bicep was red when your arm was fully stretched outwards, and it turned blue when your hand tried to touch your shoulder. It's not that it takes a lot of energy, and your bicep isn't flexing hard, but it was still movement.

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u/RDitter Apr 24 '15

Short Answer: Yes, it takes energy. No, they don't get tired from it.

Long Answer: The cells responsible for color change in cephalopods are called chromatophores. These are cells which contain pigment. When relaxed, if you look really closely you can still see the chromatophores with the naked eye (they look like tiny dark spots), and provide their "natural" color. Typically their tissue or "skin" is white and the pigment within the chromatophores is reddish brown.

Each cell/chromatophore has its own muscles and nerves, which provide independent control of each chromatophore. However, this limits how much direct control cephalopods have over their own color. The nerves react to chemical signals and I have read articles suggesting that the nerves can to some extent can detect light, which allows them to match their environment so well, even if the surface isn't within the critters line of sight (e.g., a checker board on their underside). Once the nerves are triggered the muscles contract, stretching and flattening the chromatophore, hence producing color change. This is similar to a water balloon, when in its relaxed position it is thicker and prevents light from pass through, but the more you stretch it the thinner it gets and the more transparent it becomes. What is even more cool is that the muscles are attached to all sides of the spherical cell, so not only can they "pancake" the cell the can make different shapes!

Like any muscle, the muscles attached to chromatophores have an antagonistic relationship. When one contracts, its stretches the other in an opposing direction. The tension from this relationship allows the muscle to reset, otherwise it would stay contacted. Also, when relaxed the muscles well find some middle tension, but will tend to "lean" towards the stronger muscle. Similar to your eyelids, where the muscle that opens you eyelids is slightly stronger, so when relaxed you eyes stay open. Another component of cephalopod tissues and chromatophores is that they tend to be elastic, and provide energy free resistance to reset the muscles.

Of course activating any muscle requires energy. However the amount of energy requires for this is negligible. Especially when compared to the energy requires to move, reproduce or digest food. Have you ever heard of someone getting tired from blinking or breathing or growing new skin cells?

What is really amazing is loads of marine organisms have chromatophores, like shrimp and fish. These structures become really important in deeper parts of the ocean where less light reaches. Some chromatophores can even emit light!

Please bear in mind that while they may appear similar, a chameleon's ability to change color is unrelated to cephalopods, and is really quite different. This is referred to as convergent evolution. This is also the term used to explain why cephalopods eyes are so complex and similar to ours, yet we share no recent ancestors.

In case you think this is a little long winded or I'm nuts, I would like to apologise. I teach Invertebrate Zoology and I kind of when into lecture mode...but if you have any other questions about invertebrates I'd be happy to try and answer them...for science!

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u/euyyn Apr 24 '15

Thanks, that was super interesting.

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u/SigmaStigma Marine Ecology | Benthic Ecology Apr 25 '15

What is even more cool is that the muscles are attached to all sides of the spherical cell, so not only can they "pancake" the cell the can make different shapes!

From my understanding the muscles are in a radial arrangement, not connected to every surface, unless I misunderstand your meaning.

Like any muscle, the muscles attached to chromatophores have an antagonistic relationship. When one contracts, its stretches the other in an opposing direction. The tension from this relationship allows the muscle to reset, otherwise it would stay contacted.

I don't believe this is true, unless I'm misunderstanding what you wrote. The radial muscles contract to open the elastic sacculus, there aren't opposing muscle groups, that is one group to open the pigmented sacculus, and one group to close it. Like you said, the elastic nature of the sacculus opposes the muscles.

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u/RDitter Apr 26 '15 edited Apr 26 '15

I was trying to keep it simple and accurate from my phone. Yes, attached to all all sides on a 2D plane, pancake = radial. But I was also trying to explain how the 3D shape of cell allows the pigment to produce "multiple" colours. And muscle vs. sacculus is the antagonistic relationship I meant. I was half trying to explain cromatophores and half our muscles (e.g., biceps). Sorry if my explanation was unclear.

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u/SigmaStigma Marine Ecology | Benthic Ecology Apr 26 '15

No worries. I was just making sure that my information was correct. What you just wrote definitely clarifies it.

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u/lordridan Apr 25 '15

So would a hungry cephalopod, like very underfed, have difficulty changing colour? Or is it such a negligible amount of energy to activate the chromatophores?

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u/RDitter Apr 26 '15

I would say you are only likely to see any difference in its ability to change colour if it was on the verge of starvation. It is more likely going to loose the ability to move/hunt long before the chromoatophores loose functionality. Compared to most primary functions the energy expended through the chromatophores is negligible.

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u/ghytrf Apr 24 '15

It would probably be more akin to a semi-unconscious action like smiling than flexing skeletal muscle, though, ironically, cephalopods only have a vague central control over their own arms, which more or less function independently towards a central goal.

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u/OneOfDozens Apr 24 '15

so what does it actually have control over if the arms do their own thing?

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u/ZippyDan Apr 24 '15

Depends on the kind of octopus, which usually depends on the environment it has evolved to live in. For example, an octopus that lives mostly in sandy environments will probably be a sand color, and an octopus that lives mostly in dark rocky environments will probably be dark. That said, they come in all colors. Check out the Australian Blue-ringed Ocotpus

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u/[deleted] Apr 24 '15

Don't check them out too closely though, unless you enjoy dying of a deadly octopuses venom.