IS YOUR RED, THE SAME AS MY RED?
Probably not, we humans may have an average number of cones and rod cells, but it's an average, you would see a slightly different shade of red - that's unless you are asking this question to your dog, dog's can't distinguish red from green, only blue and yellow light, so it would probably ask you back "what's red?"...
Anyway, would this question even make sense to an alien - if it's entire biology evolved isolated from Earth's, going through different biological traumas, when even a small difference in a couple million years of such an event like the extinction of dinosaurs, could have led Earth's current biosphere into a different path...
Vision have evolved as many as 40 times along Metazoan evolution, from an evolutionary point of view, eyes in general only make sense if there is something to see, if it's physically possible and practical to an animal's survival.
Wi-Fi vision makes sense in the city environment, which is dumped with internet and other radio signals, however, Wi-Fi does not interact with many types objects and not in a useful way when it does - it interacts with metal structures that are dense enough or that are within the same order of magnitude of it's wavelength, this kind of vision does not differentiate between objects behind or in front of walls, or soil. As well, the structure required to detect radio would have to be as big as satellite dish made of many small antennae on the order of magnitude of the wavelength you want to detect, and from the right material to interact with, and have a way to infer the direction of incoming light - so your 'eye' can be arranged in a detector grid in order to form an image - could usually be made by blocking the light in someway, but again, Wi-Fi passes through most materials - the sheer size and engineering behind such an apparatus is too impractical for natural means of vision when evolution can come up with cheaper and more efficient ideas.
When it comes to life on Earth, even though the eye evolved dozens of times, the general environment remained the same, requiring pretty much the same general biochemical solutions to allow vision - often in the form of Opsin and Retinal.
Notice what are the available wavelengths after the atmosphere filters out incoming sunlight
It makes sense for life to use the wavelengths of light that penetrate further into the atmosphere, of course, inside their biological and physical constraints.
Earth in Visible light (left), compared to the same shot in Infrared (right), notice how the atmosphere is now much more opaque, and thus, fewer of this infrared light is able to reach the ground
A comparably wide infrared window exists on the scale of 8~14 micrometers (about the same wavelength emitted by human body-heat), however it's dimmer, and far from what I could find about animal infrared vision - which can be sensitive as far to NIR (760nm~1500nm), ie, not even close to that window.
WHAT ABOUT A SNAKE'S HEAT SENSING?
The pit organ of two different snakes
Vipers, Pythons and Boas do have heat sensing for wavelengths between 5 and 30 micrometers, however, it's due to an organ on the front of their heads, which is connected to the visual part of the brain, the pit organ by itself produces a poor resolution image that is "overlaid" on the snake's vision, the pit organ also fails to properly detect prey of various sizes, as it uses the differences in heat sensing to point the prey's direction (pretty much how our brain uses the millisecond delay in sound receiving from each ear to tell us the direction from which it is coming), a large prey would normally trigger all the pit organ sensors at the same time and with pretty much the same intensity, small prey far enough from the snake could use the lack of resolution to it's advantage and blend within the environment - the pit organ's data latency is also limited to 50~150ms depending the state of the animal.
The pit organ main function in this sense - is not seeing (is not a proper eye), but being an auxiliary apparatus to the visual one of the snake. So aside from true heat sensing vision, a snake sees the environment with it's eyes and a slight thermal aura on warm objects.
"Because the pit receives direct input from the somatosensory, rather than the visual system, it seems likely that infrared signals are detected through a thermotransduction, rather than phototransduction mechanism."
"Our results demonstrate that the pit membrane serves as a passive antenna for radiant heat, transducing thermal energy to heat-sensitive channels on embedded nerve fibers." - [source]
CHEMISTRY OF VISION
Other than a few narrow specific bands of infrared, and the infrared window (which is a great stretch), the other viable bands of light to explore in vision are Visible light and UV-A.
Those, other than relying on the hot-wiring of heat-sensitive nerves to the visual cortex, use a complex chain of chemical reactions between light, opsins and retinal, from simple ocelli like those of small invertebrates to camera-like eyes of octopuses and humans.
Steve Mould does a great work explaining quite simply how this process works.
You can also read these papers if you are interested in further reading of this process.
The band that encompasses UV-A, Visible light, and NIR behave in similar ways with the environment, and are more likely to be used by life - how much of those is more dependent of their history and environment.
THE TAMARUTACA MYTH
Odontodactylus Scyllarus Mantis Shrimp
A.K.A. the Mantis Shrimp, it is a well known animal for it's supposedly 'super vision', lots of popular sites and YouTube channels would have you to believe it can dwarf human perception of color, after all, the animal does have 12 types of cones, however, a study published in the Science vol.343 (also shared by Nature) showed that Tamarutacas trained to associate food with color (pick the right color and you gain food thing) just can't distinguish between colors 25~12nm apart, which may sound like a nitpick stretch, except when we remember humans can tell colors up to 5~1nm apart. It turns out that the amount of cone receptors compensate for the lack of post processing capability of the shrimp's brain, and thus providing the animal with extra time to think on it's next move.
While we see this...
...The Mantis Shrimp sees "this"
(sharpened image and reduced color palette)
THE 'LIGHT SWITCH' EFFECT
This GIF resumes quite nicely the Light Switch effect theory
Is the theory that tries to justify the Cambrian Explosion - even though by the day I'm writing this, is still debated whether it was really a diversification boom as we depict, or if it just happens that there wasn't good conditions for fossilization of those animals for a long time, when these conditions came, it gives us the impression that life diversity suddenly skyrocketed in a period of a couple million years - still, considering there was indeed a boom in life diversity, how did it happen?
What we know about life evolution tells us that somehow the environment of the creatures changed in a way that favored a certain group of strategies, this change can be sudden (in geological terms) or gradual like natural climate change - like, how mammal diversity suddenly seem to boom after the KT event. In this case, the Light Switch theory suggests that atmospheric changes in composition allowed over time that more light could reach Earth's surface, and with such, animal life started to use this light to it's advantage, developing simple eyes, and with the advent of more complex eyes, predation, and mating took off as easier, and these new environmental pressure was the fuse to the ~~Caaaaambrian Explosion~~
However, what the Light Switch theory seemingly fails to explain, or at least, agree to - is in what time window would this have happened, as the Cambrian explosion seems to be offset in a few million years from the advent of eyes.
"The rate of eye evolution is difficult to estimate, because the fossil record, particularly of the lower Cambrian, is poor. How fast a circular patch of photoreceptor cells can evolve into a fully functional vertebrate eye has been estimated based on rates of mutation, relative advantage to the organism, and natural selection. However, the time needed for each state was consistently overestimated and the generation time was set to one year, which is common in small animals. Even with these pessimistic values, the vertebrate eye would still evolve from a patch of photoreceptor cells in less than 364,000 years." [Wiki]Vision was around since the Late Ediacaran, and there is
More about the Cambrian Explosion and the origin of Eyes
THE CASE FOR PAART
On my original post about vision, I stated that animals like Lisa could make use of a special rod with a bismuth compound, which reaction with UV light would make re-emit light in the range detectable to the animal's cones (pretty much a fluorescent photo-multiplier), however, given the research I did for this post, I've found no such chemical that not only wouldn't be toxic or too reactive for this purpose, such as retinal tends to be, still, this task could still be performed not by a rod or cone cell, but by a tapetum lucidum in the back of the animal's eye, by synthesizing hard bismuth compounds in the form of small crystals reflecting light, like a chameleon's guanine crystals, using such a crystal like K3Bi2I9 (a type of perovskite) which happens to also be a photovoltaic material with high absorption to wavelengths less than 600nm and UV-A, peaking within the 440~520nm band, which includes Vol' peak emission at 493nm.
And thus not by a rod, but by an array of nerves and nano-crystals in the animal's retina, they are allowed sense much of incoming ultraviolet light - if the crystals were on the order of 200nm wide, there could be arrangements of ~3k crystals per mm in a retina that is about 4cm wide, by comparison human cones are arranged in 40k per mm, however the reflective properties of the crystal lattice would improve orange/red light absorption by the cones, while catching peak emission and UV-A light that got through the cones, and would otherwise be simply lost in the animal's tissues, this characteristic comes to be very useful as Paart turns out to be a relatively dark world (receiving 64% of Earth's light), maybe as to be present in most of life forms.
Technically, such an animal would still be trichromat (red, orange and green), with the addition that it can actually sense blue and UV-A though not through either cones or rods, and not as well as us humans do, such a creature would also have some problems differentiating blue from indigo, or sky-blue from prussian-blue, or just blue from UV for instance, because there is an entire band of light 200nm wide that can stimulate the perovskite nano-crystals the same way, except for the particular 490nm peak in which it is particularly more sensible to.
Normalization of light sensitivity (arbitrary intensity) according to wavelength (nm)
Here is a comparative perception of color by Humans (Above) and Lisa (Below)
Notice how this animal has a relatively accurate green/yellow/red perception, but makes poor distinction between blue/green and blue, blue and UV light
If you may opt for, it could be said that those creatures see blue and UV light in shades of gray - varying mainly in intensity, the closest you may experience to Lisa's vision then would be an overcast and foggy day.
- M.O. Valent, 25/04/2020
- M.O. Valent, updated in 30/04/2020
- M.O. Valent, updated in 30/04/2020
