Why blue animals are so rare | Hacker News Reader

Why blue animals are so rare

popsci.com

87 pointsqiakai70 comments

>Organisms that appear blue must absorb very small amounts of energy, while reflecting high-energy blue light. Since penetrating the molecules that are capable of absorbing this energy is a complex process, the color blue is less common than other colors in the natural world.

I’m not a biologist, but these sentences immediately reminded me of reading articles about my company/technology after press briefings and feeling like they butchered a basic concept (or more correctly, I failed to explain it in an accessible way). Like, the sentences are grammatically correct but don’t make technical sense.

You’re not wrong. It appears to be a very garbled technical explanation. Mainly that organisms need to absorb low frequency/energy light while reflecting higher frequency/energy light. I’m guessing that chemically that’s harder to do.

I think this is closer to what was intended:

Molecules that appear blue must absorb very small amounts of energy, while reflecting high-energy blue light. Since assembling the molecules that are capable of absorbing this energy is a complex process, the color blue is less common than other colors in the natural world.

The linked post—<https://set.adelaide.edu.au/news/list/2019/08/20/why-is-the-...>—is much better about answering the question, rather than listing some examples.

Basically:

- Blue is rare in plants since it means leaving high energy behind.

- Many animals are a color because of there food, and see above.

- Thus, any blue is trickier, and usually done via scattering and mixing rather than a pigment. "The only exception in nature is the obrina olivewing butterfly, which is the only known animal to produce a true blue pigment."

> "The only exception in nature is the obrina olivewing butterfly, which is the only known animal to produce a true blue pigment."

That is a bold claim, but a false one. A few butterfly species share that pigment. Mussels also have other blue pigments based in carothenes that don't depend on iridiscence.

Also, there is a snail that was revered millennia ago for some blue ink that could be extracted from it. Several religions, notably Judaism among them because it is still around today, attach significance to this difficult-to-obtain colour.

That's the dye from Hexaplex Trunculus, but it's more of a bluish purple than a true blue. There seems to be modern ways to turn it into a true blue, but whether the ancients had an unknown method is debated and unproven. It's worth noting that colour names in ancient times were a lot more blurry than now (the famous sea the colour of wine of Homer), and blue is still one of the most blurry.

The article mentions plants too. But I can list a number of blue plants in my vicinity (OK, sometimes a touch of purple too) or even in the garden:

[Centaurea cyanus](https://en.wikipedia.org/wiki/Centaurea_cyanus?wprov=sfla1)

[Digitalis](https://en.wikipedia.org/wiki/Digitalis?wprov=sfla1)

[Centaurea](https://en.wikipedia.org/wiki/Centaurea?wprov=sfla1)

[Scabiosa](https://en.wikipedia.org/wiki/Scabiosa?wprov=sfla1)

[Phacelia](https://en.wikipedia.org/wiki/Phacelia?wprov=sfla1)

and last but not least many varieties of [Campanula](https://en.wikipedia.org/wiki/Campanula?wprov=sfla1)

3 of those I would call purple rather than blue.

I agree, but purple seems to be a similarly rare color IMO.

I could offer

[Chicory](https://en.wikipedia.org/wiki/Chicory?wprov=sfla1), [Myosotis](https://en.wikipedia.org/wiki/Myosotis?wprov=sfla1) and [Borage](https://en.wikipedia.org/wiki/Borage?wprov=sfla1)

as replacements ...

Some flowers are blue indeed.

They are made to stand out, so it is like they are a purposeful exception to the rule

Blue flowers are extremely common because pollinators are attracted to them.

I am pretty sure that they were referring to the plant itself being blue (like leaves and stems), not the flowers.

Here’s a good answer from SE: https://biology.stackexchange.com/questions/56476/why-are-so... (spoiler: we don’t know). But the second answer speculates that blue light was the most available to the ancestors of current plants (due to properties of Earth’s atmosphere) so they evolved to absorb it.

Related question is why plants are green: https://biology.stackexchange.com/questions/450/why-do-plant...

My favourite flower, which I have just discovered: Phacelia (blue/violet color) ( https://en.wikipedia.org/wiki/Phacelia_tanacetifolia )

1) Seeds easy to find in most stores.

2) Each strand has an array of flowers which bloom serially => quite long blooming timespan (and damage by bad weather is limited if it affected only the flowers).

3) Bumblebees absolutely love them (this year I put exclusively Phacelia seeds into 1 of my 2 big pots on the balcony, with max seed density, and often there were up to 10 bumblebees at once per pot checking them), and I absolutely love bumblebees (they look clumsy, they're kind of funny + they absolutely ignore me, respectively when they happen to fly in my direction and they notice me they take a turn as soon as their flight envelope allows them to)

4) This might be just random or caused by some other factor like weather/neighbours/whatever, anyway:

since I planted this year Phacelia flowers and the bumblebees started coming I have hardly seen any wasps nor especially hornets (I've seen twice a hornet flying by, but it took a large curve from my balcony - during the same timespan at the other sides of my flat I noticed four times hornets investigating in front of the windows). Last year (without Phacelia/bumblebees) I had a lot more problems with wasps&hornets => maybe wasps & hornets noticed the bumblebees and thought "ah, already taken/busy!" and therefore marked my balcony as a no-go zone?

EDIT:

I recommend the app "PlantNet" for Android ( https://play.google.com/store/apps/dev?id=829216199869931637... ) & iOS ( https://apps.apple.com/ch/app/plantnet/id600547573 ): take a picture of your plant/flower and you get the name.

Fascinating article. But early on I had one question - why is a blue that is made by sunlight hitting hair nanostructures considered a "simulation" thereby differentiating it from color made through sunlight interaction with biochemistry of surfaces and subsurfaces?

To draw that out further, by the same logic we might consider properties of human-made metamaterials also simulations?

I believe all of the colors of butterfly wings, and of all feathered animals are produced in the same way? I've always assumed that "simulation" has a local definition in the study of biological color reproduction, where light interactions with ultra fine structure at the atomic level is the default, or perhaps maybe on the time scale of evolution, the oldest means of reproducing color.

Contrast this witb a much coarser structural phenomenon manifesting at a level much closer to macroscopic is thus considered to be a "cheaper" simulation of that effect, in order to derive its same selective benefits but with less of a radical genetic shift required for the production of the right proteins etc.

The article says "manipulate the light that shines on them that simulates their signature blue look". https://en.wiktionary.org/wiki/simulation meaning number 4, "Assuming an appearance which is feigned, or not true.".

I believe what they are trying to communicate (pretty poorly) is that the hairs are not blue as such, but in certain circumstances can manipulate light into the blue-violet spectrum.

Think of it this way: a prism isn't any of the rainbow colors, but can manipulate light into such.

On a related note, blue LEDs are also the most rare, for engineering reasons, and their production led to a Nobel Prize: https://www.nobelprize.org/prizes/physics/2014/press-release...

Video about the history of blue LEDs by veritasium:

https://youtube.com/watch?v=AF8d72mA41M

"...once Nakamura succeeded in creating a commercially viable prototype, 3 orders of magnitude (1000 times) brighter than previously successful blue LEDs, Nichia pursued developing the marketable product. The company's gross receipt surged from just over ¥20 billion (≈US$200 million) in 1993 to ¥80 billion (≈US$800 million) by 2001, 60 percent of which was accounted for by sales of blue LED products."

And IIRC, in return for that he got a $180 bonus from his employer, and a bit later, a Nobel prize.

Reminder to everyone:

Plants are green(On earth) because they reflect the green color (which the sun spectrum is strongest) because they have probably adapted to better regulate different lightning condition during the day, for this they use two different pigments (chlorophyll a(blue), chlorophyll b(red); or other pairs)

One of the best ways to improve crop yields via genetic engineering might be to create black plants.

If that was optimal, I would expect it would be the standard by now. Not through genetic engineer, but through basic evolution over millions of years.

Evolution is optimizing for survival, not crop yield.

Exactly; see pollinators comment above. Although as tech progresses... perhaps we can make black plants as attractive to genetically modified pollinators. Do I sense a slippery slope here?

Having more energy available (all things being equal which they aren't) is advantous to both survival and crop yields.

only if more energy doesnt come at the cost of something else, like water retention

That will only be the case if light absorbence is the primary limiting factor for the plant. If something else is a bigger limiting factor (e.g., nutrients, pests, water, temperature, pollinators, and so on), then a more darkly colored plant will not be meaningfully more likely to survive and reproduce than its lightly colored neighbors.

Outside of human-directed breeding, we typically only see darkly colored plants in locations with low light and with few other evolutionary pressures: deep understory tropical plants, for example.

Meanwhile, in locations with high light and other evolutionary pressures, plants can sometimes evolve to be quite pale. For example, desert succulents are often very light colors because they need to deflect light to keep cool and preserve water.

I honestly doubt it’s in a global optimum, as evolution is easily stuck in decent local minima.

Simple example: “C4 carbon fixation”, which allows photosynthesis to proceed with much less water available, only evolved ~30 million years ago. This was the revolution that allowed modern grasses to emerge, and thus changed enormous barren deserts into the savannahs that early humans made their home. Despite being such an improvement, this is not yet a “standard”; trees, for example, still use the “old” inefficient “C3 carbon fixation”.

Despite photosynthesis having been around for hundreds of millions of years, fundamental improvements still happened just 30 million years ago. I would suspect that there is more that can still be improved.

My favorite blue animal:

https://duckduckgo.com/?t=h_&q=Dendrobates+Tinctorius+Azureu...

The Sinai agama turns blue during the breeding season to attract females and it might be why blue connote to ribaldry

Glaucus atlanticus

My cousin wrote a book about this topic (it is not only about blue animals but the general scarcity of blue in the natural environment): https://www.amazon.de/Blue-Science-Secrets-Natures-English-e...

I never gave this much thought before but the book quite successfully managed to interest me in its subject and lead to me understanding some of the underlying mechanisms (which lay all outside my domain as a software developer).

Reminds me of Truite au Bleu or blue trout. It’s a recipe for cooking fresh trout which supposedly originated in the Alps.

“Why Trout Is Turning Blue in an Old Garage in Queens”

It’s the best way to cook trout. You’re welcome.

https://www.vice.com/en/article/kbxdv9/why-trout-is-turning-...

Isn't it pretty common in marine animals?

Lots of fish, dolphins, whales, etc. Or do they count as grey?

Only cartoon fish are blue.

Blue tang?

There are two interesting cases of blue fish in my home state.

1. The Beardslee Trout, which exists only in a single lake in the world: https://en.wikipedia.org/wiki/Beardslee_trout. Most photos online of these fish, including the Wikipedia thumbnail, are not representative of the stunning color of these fish in person, and are most likely not Beardslees at all. The lake itself looks like blue gatorade, and the fish have obviously adapted accordingly.

2. Lingcod, a fraction of which are a crazy alien blue color not only outside but throughout the flesh. https://oregonmarinereserves.com/2021/08/31/lingcod/. This phenomenon applies to a handful of species, but lingcod is the most well-known.

Also think so. Plenty of fish are vibrant blue, the blue whale is grayish blue but still blue.

Also plenty of birds are blue are they not?

And I totally forgot about butterflies and other insects as well

One in two million lobsters is blue https://allthatsinteresting.com/blue-lobster

Someone told me that chefs use blue bandaids, because there is no blue food.

Not just colored blue, but embedded metal to be detectable

https://www.reddit.com/r/todayilearned/comments/5dg5qs/til_t...

Blue jays are a pretty easy example of structural coloration

Are blue animals rare? They are certainly not that rare as a casual search turns up hundreds of photos of blue lizards, butterflies, Beatles, spiders, birds, starfish, fish, whales, sharks, and other miscellaneous sea and land creatures.

As for animals, they need to avoid predators. I'd say that blue isn't the best color to hide in most areas. So selection should favor other colors, unless the color is used as a warning, e.g. to signal a poisonous creature.

Also IIRC (and cursory searches seem to agree) blue is the most common/prominent color other animals see

"Unlike other bees, they prefer to live alone and not in busy hives. "

IIRC, the vast majority of bees are solitary (90%?)

Is that 90% of bees, or 90% of bee species? I think around 90% of the bees I see are of a non-solitary species.

Green snakes are technically blue. They have yellow pigments together with a blue scales.

After their death, the yellow pigments fade, leaving a blue husk of a snake.

There are also no blue pigments in any plant. The various blueish flowers use other tricks to reflect blue light.

To be fair, indigo is a blue pigment and it is present in many different plant species. (Mind you, it does not make the plant blue; it only becomes blue after exposure to oxygen.)

blueberries.

and the pH sensitive stuff in red cabbage juice.

While growing up in Asian country, butterfly pea plants with bright blue flowers were common.

They make an amazing brilliant tea!

or was it ... the white jade bush?

No, butterfly tea: https://i.pinimg.com/originals/2c/ac/2c/2cac2c42209b54ab9daa...

If you add an acid to it (like lemon or lime) it turns to the beautiful purple colour you see on the right.

But I think there may be a joke going over my head here...

Hmm, interesting. I thought it was like with popsicles, how the blue ones get eaten first.

Just saw a Blue Jay last week.

Chicory has nice blue flowers.

Both are common in Chicagoland.

There are many birds which are blue, but none of them have blue pigments [1]. It's a light-scattering effect.

[1] https://blog.education.nationalgeographic.org/2016/05/09/the...

Important bit from the article:

When white light strikes a blue feather, the keratin pattern causes red and yellow wavelengths to cancel each other out, while blue wavelengths of light reinforce and amplify one another and reflect back to the beholder’s eye … [D]ifferent shapes and sizes of these air pockets and keratin make different shades of blue.”

All color is a light scattering effect.. this article makes zero sense to me..

https://en.wikipedia.org/wiki/Structural_coloration seems like a decent explanation.

The best explanation I’ve read is Feynman’s delightful QED.

Haha OK, some avian plumage enthusiasts might find that a bit of a detour though!

I was hoping to see something about velella, they have a shockingly brilliant blue.

Weird that this website seems broken with an un dismissable popup on an iphone… not exactly a rare user device.

lots of blue birds

"Blue birds, blue jays, cerulean warblers, peacocks: all blue birds, but none of them are actually blue"

I stand corrected

> none of them are actually blue

The article is just trying to be controversial or something; they are actually blue. Structure colors are no less real than pigment colors. It's not an optical illusion or some glitch in human perception, bounce white light off a bluejay and pass it through a prism, a strong blue line will be apparent. That blue light really is there, therefore they really are blue.

This notion that only colors coming from pigments are true colors is completely arbitrary nonsense.

They're "true colors" but they aren't the same. Pigment colors you can generally grind up and turn into a paint, structural colors not so much. Structural colors are also often angle and polarization sensitive, not so with pigment colors.

prompt to ChatGPT 4o:

there are very few blue colored animals. also it was very difficult to develop LEDs emitting blue colored light. are those two observations technically related? can you summarize the technical relationship in a paragraph of few sentences?

answer:

The rarity of blue color in animals and the difficulty in developing blue LEDs are technically related due to the higher energy associated with blue light. Producing materials or structures that can efficiently emit or reflect blue light is challenging because blue light has shorter wavelengths and higher energy, requiring precise and stable materials. In animals, this results in the reliance on complex structural coloration rather than pigments. Similarly, the development of blue LEDs required breakthroughs in materials science to create stable semiconductors capable of emitting high-energy blue light, such as gallium nitride.

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