Basically, I have creatures that are supposed to see all wavelengths of light which are hypothetically visible to biological life, but the way they do this is by changing the photo-receptors in their eyes so that they change what colors they see. Now, I know the human eye does turn off photo-receptors when it is dark, but my question is if a species could reasonably consciously control this process so that they change what colors they see by purely biological means or if magic is necessary.
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1$\begingroup$ So, to be clear, you want them to be able to stop seeing certain colours and see other colours instead, at will? Rather than just seeing all the colours all the time? 'cause if the latter's what you're after, the Mantis Shrimp has you covered. $\endgroup$– jdunlopJul 21 at 0:37
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$\begingroup$ I can see the biological (evolutionary) advantage to turning off receptors unecessary for night vision - they'd clutter up the vision trying to "see" wavelengths that aren't there. I can also see the a lifeform evolving the ability to see a much (even much) wider range of wavelengths - but what would be the point of willingly turning off receptors when the light they're designed to see is there? Understanding a bit more about how this ability would be used would help with a rationalization for how it works. $\endgroup$– JBHJul 21 at 1:28
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$\begingroup$ I believe that rather than photo receptors 'turning off' at night, there just isn't enough light available to trigger them. $\endgroup$– Michael RichardsonJul 21 at 13:56
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$\begingroup$ Not quite a "conscious" control of the color you see, but people with chromesthesia see different colors depending on their other senses. If you play the right music, you could perhaps have some sort of control over it. $\endgroup$– TortlienaAug 8 at 9:54
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2 Answers
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It is possible. The eye has been 'invented' many times for different life-forms on earth.
We have three colour vision receptors, commonly labelled S (short wavelength = blue), M (medium wavelength = green), and L (long wavelength = red). These all use the bleaching of an opsin dye to generate a signal.
The S opsin is possibly the oldest. It may predate multicellular life. It has been suggested that the blue L-opsin was used as a precursor to photosynthesis, as it can convert light into electron potential.
We share our S and L vision with most animals that see, including the jawless lamprey, which suggests they are 500 million years old; almost as old as multicellular life. The L vision is concentrated around the optic centre, where the S vision goes to the periphery, so it may be S vision evolved after the lens, and L vision came before.
Our low light level detection probably came next. This uses a different opsin (Rhodopsin), with several cunning tricks to extend the sensitivity to very low light levels. It is suggested that early mammals may have become nocturnal 200 million years ago to avoid dinosaurs.
The L vision split into L and M vision about 30-40 million years ago. Old world monkeys have 3-channel vision, and New World monkeys have 2. Both L and M have genetic variants which give us all the different anomalous forms of colour vision.
It seems that the night vision has little interaction with our normal colour vision. There is a small illumination range for mezopic vision where we can see detail with our night vision cells (except for the vision centre, which has none), and fill in a bit of colour from the cone cells.
It seems we have four basic vision systems. The Scone vision is the oldest. The rod cells do the night vision. The L and M cone vision colour signals are generated in the retina. The S cone cells also generate colour signals in the retina, but the coupling is more complex as there are fewer S-cones, and none in the fovea.
When people used gene therapy to vision channel using genetic give a third channel to squirrel monkeys, they learned to use them. It seems likely that we could learn to use extra channels if we were provided with them. Which is the exact opposite of your question, but it suggests if we were to have an advantage in ignoring one channel, then we might learn to do so.
The Mantis Shrimp is a very different beast. It has sixteen vision channels at the last count. I would rather doubt that it has a 16-dimensioned understanding of colour space. I suspect it uses all these channels to detect camouflaged prey, because it is hard to match all the wavelengths from infra-red to ultra-violet.
The human eye does not turn off night vision. There are people who only. have night vision. They can use it in full daylight, though they do not like it. See Oliver Sacks' book The Island of the Colorblind. Our different vision systems are linked together in complex ways, so it is not like pulling out the Blue BNC cabe from your monitor. But if we needed to ignore a particular signal, we could probably train ourselves to do so.
You can turn off bands of colour vision using coloured glasses. Our central vision has no blue S-cones, and is protected from short wavelengths by the yellow macular dye.
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No, you can just use biological/neurological means.
Your brain already does a bunch of filtering, so a species being able to consciously filter out colours, or change them, isn't really that much of a stretch. You'll usually notice it with things like the Checkboard Illusion, certain patterns, or the famous blue/gold dress.
It's not quite changing the receptors in the eye, but the end result is the same, and could be achieved with conscious control.
