Creature Feature: The Physics of Animal Color

An episode of Creature Feature where Daniel and Katie talk about the physics of how animals look so brilliant, and how some people can see in the UV.

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Episode Transcript

Speaker 1 (00:06):
Welcome to Creature, feature production of I Heart Radio. I'm
your host of Many Parasites, Katie Golden. I studied psychology
and evolutionary biology, and today on the show we're talking
about all the beautiful colors and nature. Blues and greens
and reds and browns and purples and ultra violet. There

(00:27):
are so many colors in the annual Kingdom and in
the natural world. But it is really interesting how these
colors are actually produced, and it's not always straightforward, and
in fact, what we see with our human eyeballs may
not be what other animals see with their incredible eyeballs.

(00:48):
Discover this and more as we answer the age old
question is there a berry that's so incredibly blue it's
just gonna trick you into doing its dirty work? Joining
me today is friend of the podcast who I have
been on his podcast quite a bit. Post of the
Amazing Physics podcast Daniel and Jorge explain the Universe and

(01:13):
particle physicist Daniel whiteson Welcome. Hello, Hello, very glad to
be here. Although I can't boast to be host to
any parasites as far as I know, as far as
you know, although you probably have some demodecs parasites on
your eyelashes, as do most people. I contain multitudes. I
suppose little societies living on our eyelashes. Is there anything

(01:37):
cuter than that? Well, me and my little societies are
very excited to be here to talk to you about
colors in the natural world. Yes, so I thought this
would be right up your alley, because we are talking
about the physics of colors in nature. Because you know,
when you see a color, it feels pretty straightforward that

(01:58):
thing is just somehow painted that color. But it is
actually much more complex how it works in nature. Things
aren't just kind of painted with a paintbrush. And in fact,
there are some incredible ways that colors present themselves, in
incredible ways that animals will perceive these colors like an

(02:19):
entirely hidden secret world that we never really knew about
until researchers started investigating it. So first we will go
over how color exists in living organisms. So this is
an animals and plants, even fungi. There are a few

(02:40):
ways that color occurs. So when you think of color
in the natural Kingdom, Daniel, what what do you think of? Like,
what is sort of the first thing that comes to mind.
I think of the incredible colors of flowers and the
incredible colors of insects and words, and I wonder why

(03:02):
they're there and whether those animals see them the same
way we do. You know. I wonder why we live
in a world that we find beautiful, if we could
have evolved in a world that we found like boring
and drab, or if we just sort of naturally react
to any world we discover with amazement and satisfaction. Yeah,
this is what's so interesting to me, because I think

(03:25):
one tempting thing to think is that humans are the
only animals capable of appreciating beauty and color in the world,
that we're the only ones who, you know, really enjoy
the site of a flower. But as we'll talk about,
that may not really be true that we One of
the things that we may share with many other animals

(03:48):
is their dependence on color, their appreciation for it, and
how that beauty of the world serves a very important
function for for organism survive all. So, there are two
main types of color in the animal kingdom, pigments and
structural coloration. So pigments. Pigmentation is pretty straightforward and probably

(04:15):
what you think of when you think of something that
has some color to it. So pigments are substances produced
by cells that will absorb certain certain wavelengths of light.
The light that is not absorbed is reflected back to
your eyes. So that's how you see something that is pigmented,

(04:37):
how you see that color. So pigments can be found
in nearly every organism, from flowers to birds, to fish,
to mammals to fungi. It's everywhere in the animal kingdom,
and that is typically what gives things their color. And
you say that simplistic, but actually aren't there several fascinating

(04:57):
levels of signs there? I mean, as the physical is here,
it amazes me to think about, like the microscopic process
that happens when your eyes sees red. I remember as
a kid thinking about, like what is red about that light?
Is the light itself? Red is happening in my head?
That makes me feel red? Did somebody else see red
the same way? There's a whole lot of really fascinating

(05:19):
questions there. Yeah. Absolutely, it's really interesting too to think
about how something that is a certain color, like something
that is red, it's actually that is it is rejecting
the red wavelength that is the one color that is
not there is red, because that red is reflecting back

(05:40):
at you and that's why you see it as red.
But it's actually absorbing the other wavelengths of light. So
like in a strange kind of way, the only color
that it isn't isn't part of it is the color
that you see. Yeah, And I think for a long time,
people didn't know how vision worked. They didn't understand whether

(06:01):
light was being bounced off of things and hitting your eye.
And for a long time people were wondering if your
eyeball actually shot out rays which then bounced off something
like sampling it and came back to your eye. You know,
back before we understood how light worked, people have to
think about all sorts of crazy ideas. But I think
it's really cool to think about the actual photons. Like

(06:21):
if a photon hits your eye and you see it
as blue, or another one hits your eye and you
see it as red. And what's the actual difference in
the photons? As you said, it's the wavelength, it's how
fast they wiggle. They all travel the same speed, but
they have different speeds at which they wiggle, so they
have different wavelengths. But you know, there's an infinite spectrum
of wavelengths, like a photon can have any wavelength of

(06:43):
light that just changes how much energy it has. But
how you see it, whether it's blue or red or green,
that's just is how your brain is interpreting it inside
your head. Yeah, that's really interesting to me because there
really is. When you think about it, it's there aren't
distinct colors, right, There aren't just a certain number of
distinct colors. There is likely sort of infinite gradient of colorations,

(07:08):
but we can only maybe distinguish a small fraction of
those colors that we see because of the limitations of
our our eyeballs, which, even though I'm saying limitations are
eyeballs are one of the most incredibly complex organ in
our bodies. And it's really interesting. It is really fascinating.

(07:28):
And I remember as a kid wondering if colors are
just in my head, if my mind is sort of
painting red inside my mind's eye when that photon hits,
could my mind come up with a new color? Could
I invent some new color that hasn't wasn't inspired by
something I saw, wasn't like, you know, the color of
a bees butt, or something, um, but I never managed

(07:49):
to do it. Maybe I'm just not creative enough. I
tried to do that too. I tried to think of
a new color, and I never really could. But we will,
you know later. I'm so excited to talk about this
because we will talk about some people who may actually
be able to see color that doesn't really exist for
other people. And yes, in short, basically all of our experience,

(08:11):
right from touch to taste to color, is happening inside
of our brains. So it is an interpretation of these
photons that wiggle at a certain wavelength and then they
hit the back of our eye, and then they hit
these photoreceptor cells and will sort of, if you think
about it, kind of like tickle certain cells, Like certain

(08:32):
wavelengths are able to create sort of a domino effect
for certain cells, and then that will be sent to
the brain via a bundle of nerves and then that
is what creates the color. And it's just it's like
the most intricate Rube Goldberg device uh at work there
every time you see any kind of color, and it's

(08:54):
so helpful, right, And imagine if you couldn't see color
in the world, to be so much information out there
about the universe that you would just be missing. And
as you said earlier, there's lots of different wavelengths of
light that we don't see, which means there's a huge
amount of information about the universe that's out there that
we are just blind to. That's that's exactly right. And uh, yeah,
as we'll talk about really soon, there are animals that

(09:17):
can actually tap into that secret universe of colors that
we can only kind of conceive of. Yes, so even
though pigments are relatively straightforward, as we've talked about it is,
it's still an extremely complex, fascinating process that happens with
those So so, yes, they they are essentially their substances

(09:37):
produced by cells that will absorb wavelengths, and that the
wavelengths that they do not absorb, they reflect back out
and those hit our eye and we see that color.
But there's an there's a second type of coloration in
the animal world, in the natural world called structural coloration.

(09:58):
So these are microscopic structures that instead of absorbing light,
they will bend, refract or reflect light, causing certain wavelength
to separate and hit the eye. So they kind of
they scatter light rather than absorbing certain wavelengths. This is
super cool also because it's physics at work again. Right,

(10:20):
if you're familiar with a prism, then you know that
when white light hits it, white light being a mixture
of many different colors, that the different parts of that
white light bend at different angles because of their different frequencies.
This is something like that Newton demonstrated hundreds of years ago.
So it's pretty awesome that the natural world is like
scattering tiny prisms all over surfaces to change its color.

(10:41):
That's amazing. How do they do that sort of microscopically?
Are they actually like little prisms? Yeah? Yeah they are.
I mean think I think the Pink Floyd logo with
that it's pink Floyd. Right, you're gonna ask the physicist
for your pop science. Sorry, you're gonna ask the physicist
for your pop culture references. So you know that prism

(11:03):
will scatter light, and that is exactly right. They basically
have these tiny prisms. So these are common in things
like bird feathers or butterfly scales on their wings. So
have you ever seen like a morpho butterfly? I have
no idea what that is. It's this beautiful butterfly that

(11:28):
has this iridescent, bright, bright blue coloration on its wings,
and it's such a bright blue it looks like it's shimmering.
And it makes me think that these butterflies are maybe
where people got the idea of things like fairies or magic,
because it looks absurdly magical. So I'm a little confused
about how these structural things work, Like doesn't the color

(11:50):
of it then depend on the angle of it? Like,
is that why it's shimmering because if it turns a
little bit, the prisms are shooting red light in your
eye instead of yellow light or blue light. Yeah, that's right.
So some of these structures are such that they will
result in something like a predominantly blue wavelength because they're

(12:14):
structured that they basically amplify the blue wavelength through these
tiny prisms. But there are some of these prisms that
will result in an entire rainbow, and that color will
shift depending on the angle of your eye, the angle

(12:34):
at which you look at this organism. So there are actually, uh,
there are actually snakes that have these iridescent colors in
their scales that they look like a rainbow because they
are essentially these tiny prisms that are scattering light, and
you'll see the entire gradient through their scales, and it's

(12:58):
it's quite beautiful. You can actually see up somewhat even
with the common crow, where their feathers, these micro structures
on their feathers will basically scatter the light such that
you can see all of these different hues beyond just
the black of their feathers. You can see these other
hues of light if you view them at a certain angle.

(13:20):
That's right. Crows are awesome. They don't get enough love
I think from bird enthusiasts and from the population in general.
They're super smart. And they're not just black exactly, they're
like shimmering black. But what's the sort of history of that, Like,
have these different mechanisms for color pigmentation and structural did
they split off evolutionarily at some point? Are they totally

(13:40):
different ways to get color? Are they related to each other?
I would say that they are somewhat interwoven, because you
can have an animal that has both pigmentation and structural coloration,
So I think they're they basically worked together. So while
some some animals may not have a structural coloration too much,

(14:04):
or or maybe rely mostly on structural coloration instead of pigmentation.
You'll have many animals that will actually have both a
lot of birds, a lot of reptiles will have both
structural coloration as well as pigmentation and humans. In humans,
we mostly rely on pigmentation in terms of the coloration

(14:25):
for our skin and for our eyes and hair. But yeah,
and in a lot of other animals, you'll have this
really cool confluence of both of these. And I would
say that they probably I think that they're they would
probably in evolve in the pretty interleaved way because of

(14:47):
so there are some really interesting ways you can see this.
So in terms of the production of pigmentation in humans,
it is melanin produced by our melanna sites, and so
melano sites are a type of cell that produced the
color in our skin and our hair in our eyes.

(15:09):
But not all animals actually use melanno sites. They use chromatophores.
So chromatophores are the pigment producing cells of things like cephalopods,
so those are octopus, squid, cuttlefish. Chromatophores are also present
in reptiles, fish, amphibians, and more. And chromatophores have some

(15:32):
really interesting properties, and that is that they can use
both pigment and structural coloration, and in some of these
animals they can actually be dynamics. So most chromatophores just
simply produce a pigment and create color that way, but
some chromatophores will use structural coloration to produce hues by

(15:54):
scattering light that creates a very very vibrant version of
this color that to otherwise not be produced just by pigmentations.
So this can be seen in things like the bright
blue stripes of a zebra fish. Have you. They're actually
a very popular little aquarium fish. They're also called blue danios,

(16:15):
but they're these little, just little slips of fish, and
then they have these blue stripes and those blue are
these bright bright blue. It's hard to describe it without
seeing them in person, but it's similar to the morpho butterfly.
Where's that shimmery, shiny, bright blue. And that is a
result of both pigmentation and structural coloration that like amplifies

(16:39):
that blue. And like I was mentioning earlier, there are
those rainbow iridescent hues of the sunbeam snake that they
actually use guanting crystals in their cell structure to scatter light,
which is kind of amazing. It's this snake that has
these beautiful crystals that will amplify light and scatter it

(17:02):
so that you see these rainbow hues and chromatophores in
addition to both being able to produce structural and pigmentation,
can alter their shape and alter what pigment they are
producing in order to rapidly change color, which you see
in things like octopus, octopuses, and cuttle fish, and you

(17:26):
can also see it in things like chameleons. So yeah,
it is. It's you can see this incredible example of
how uh, pigmentation and structural coloration can work together to
create mind blowing colors in the natural world. And do
all these different creators use it for the same purpose.

(17:49):
I have a sort of simplistic understanding that sometimes birds
uses for like sexual selection, or flowers use it to
attract bees for example. Are the structural elements always using
the same way as the pigments or there a huge
variety in why these creators spend this energy to make
these amazing little structures. There is a huge variety of
purpose for these colors, So you're right, Like in birds,

(18:12):
often the coloration of birds comes down to looking pretty
for the opposite sex, for the male birds trying to
look very pretty for the females. There are a few
species where it's more equal, where both the females and
males are trying to look their prettiest. But in a
lot of animals, coloration can have many different uses, so

(18:34):
uh and chromatophores, because of how dynamic they are, actually
really illustrate this beautifully. So in octopuses or color cuttlefish,
you actually see that dynamic color shifting of their chromatophores
being used for things like camouflage or even like disruptive
coloration to evade predators. So they can use it both

(18:58):
to be able to hunt to sneak up on their
prey or to evade predators and use these kind of
distracting colors. Sometimes they'll even have these pulsating colors that
is thought to have sort of this disruptive effect at
confusing predators about the direction that the the octopus or
cuttle fish is going so that they can escape. But

(19:20):
in things like the sunbeam snake that has that beautiful
rainbow hue, it's actually not exactly known why they have
it because they don't seem to really rely on site
that much. They're mostly nocturnal, and so one of the
ideas is that that is just sort of a byproduct

(19:41):
of the structure of their scales, which may have some
other use like conservation of heat energy making, because they
are they are quote unquote cold blooded, just meaning that
they use their environment for thermal regulation to make sure
that they maintain a good would uh homeostasis of their

(20:03):
body temperature and so being able to have a structure
on your skin, the structures on their scales that may
help them mediate how much light, how much of the
heat from light is sort of reaching their bodies or
not that may be beneficial to them. That's still actually
being studied though it's not quite known why they are

(20:25):
these beautiful colors, but there's a there's a good chance
that it has nothing to do with how pretty it looks,
and they may not even really see these colors, but
that it has it's just a byproduct of the structure
of their scales that has some other benefit for them. Wow,
so they could be like accidentally glamorous. How incredibly, how

(20:47):
incredibly amazing they look, Yeah, exactly, And of course there
are other types of structural coloration that we see that
don't even use chromatophores like I was described. So that's
the case for butterfly scales, where it's just basically these
these chunky scales that use diffraction grating to produce colors.

(21:11):
So when light hits them, they diffract the light through
these microscopic slits like a physics experiment. That's amazing. That's
like a whole other way to use light to look different.
It's incredible. Yeah, So essentially, like the light goes through
these tiny slits and then it comes out as this.

(21:36):
I'm actually going to struggle more to explain this than
I imagine you might be able to explain it. But like,
how so how does It's kind of similar to like
the slit experiment, right, the double slit experiment. What happens
when light goes through a really narrow passage is essentially
that passage becomes like a little source sort of like
light is emitted from a little slit itself. That if
you have lots of little slits near each other, and

(21:58):
you have all these different sources, so now if your
eyeball is a certain distance away from all of those slits,
then some of those add up and some of those
cancel out and so you get these interference effects, like
the number of wavelengths the light has to travel from
one slit and from another slit might be an equal
number of wavelengths, in which case they add up, or
they could be off by a half wavelength, which means

(22:19):
that one is wiggling up at the same time the
other one is wiggling down, and so they cancel out.
So you can get these amazing interference patterns from these
diffraction gratings. And it's dependent also on the wavelength, so
you'll see interference in red, in other places you'll see
non interference in blue. And so it's another way, sort
of like a prism in that it's bending the light

(22:40):
and creating effects that depend on the wavelength. Yeah, I
love that. That's that is so cool that essentially, if
you want to look at a teeny tiny physics experiment,
you can look on the wings of most butterflies. So
when you're talking about interference, there can also be constructive
interference right where two wavelengths are adding up. Yeah. Absolutely,

(23:03):
If the wavelengths are an integer number apart, like if
it's wiggled nine times and another photon is wiggled ten times,
then they're sort of in the same place in their wave,
and so they add up. It's just like waves in
the ocean. You know, if two waves hit you at
the same time and they're both like pushing up, then
you're gonna get two pushes up. It's gonna be really dramatic.
So absolutely you can have constructive interference as well as

(23:25):
destructive if they're pushing in different directions. Well, constructive interference
is the reason behind the brightest blue found in any
living tissue in the world, which is produced by the
marble berry, which is a plant, which we don't We
don't often talk about plants on this show, but when
we do, they are absolutely incredible, and the marble berry

(23:48):
is a blindingly blue berry. Now, you can look this
up online and I'll certainly have a picture of it
in the show notes. But a photograph is not going
to do it justice because it's not going to capture
that blue light like your eyeballs can. And it won't
also translate the way that this these shimmer because it's

(24:08):
structural coloration. It does depend on the angle, so you'll
have this like purplely blue shimmery so bright it might
actually hurt your eyes a little bit. So this is
a leafy flowering plant from southern Africa. Its berries are
shockingly blue due to the mirror like cell structure on

(24:30):
their surface and crystalline structure underneath of spiraling cellulose. And
what it does is it allows for a huge amount
of light to be narrowed and reflected, and it amplifies
the blue wavelengths especially, and it hits your eye just
with this flood of super super blue in this constructive interference. Well,

(24:55):
I don't know if I believe that these things are
the bluest things in nature. Pretty sure that after an
entire blueberry pie one time, that my insides were the
bluest thing in nature based on you know what came
out later. But I'm wondering, are these berries blue just
in the skin or is their flesh also blue? Because
blueberries are mostly blue in the skin. When you bite inside,
they're sort of like faintly transparent. Are these guys just

(25:17):
in the skin or blue all the way through? That's
a really good question. My sense was that it is
mostly in the skin, because what is interesting about these
is that blue coloration is not an it is not
an honest indicator of them being delicious nutritious berries. They

(25:40):
do not have any nutritional value. They're not strictly speaking edible.
They don't I don't think they would make you sick, really,
but they don't taste good. They're not really good for you.
But birds love them. And the reason they love them
is a bird is going to be very easily wooed
by some pretty and colorful uh. The birds will try

(26:03):
to eat them or even decorate their nests with them
because they are just so so blue, so shiny, so shimmery,
just like humans. Essentially, these birds just love these berries
because they're pretty and they want they want to have them,
and so the berries don't have to waste resources making
themselves nutritious. They're just so shiny and pretty that birds

(26:27):
will distribute them. They will disperse them and try to
eat them, despite them not being nutritional at all. They'll
put them in their nests. And this plant then sneakily
finds a way to have itself distributed just through sheer
beauty and no actual intrinsic value. Oh man, I feel
bad for the birds. I feel bad for the birds.

(26:48):
They're getting like conned by a dumb berry. It happens
more often than you would think we're a plant outwits
an animal. The day that happens to me, I'm gonna
resign my job here as a professor. How smarted by
a unless it's a slime mold that here. Those are
pretty smart. So we've talked about some of the incredible

(27:20):
ways that you can see color in the natural world.
You have pigments which can produce amazing colors, like the
color of of our eyes, of our hair, and our
skin is through pigmentation. But there's also structural coloration which
can happen in a variety of ways, where basically it
is a structure that is manipulating the light's wavelength so

(27:44):
that it can scatter, it can amplify it, it can
cancel it out, and that can result in everything from
the bluest blue you've ever seen to a shimmery rainbow.
One thing is interesting is that as beautiful as the
world is to our eyes, it looks radically different to
other animals, and other animals will experience the world in

(28:08):
such different ways that it may even be hard for
us to imagine exactly what is going on, because, of course,
we cannot read the mind of an animal. We can
only look at their eye and look at their brain
and kind of try to piece together what maybe their experiences.
We can't even understand what another human is experiencing when

(28:30):
they look at the world and they have basically the
same biology, right, I don't know that your red is
my red and your blue is my blue, And so
to me, it seems like philosophically impossible to imagine what
an octopus or a rat or a fly might be
experiencing about the world. Yeah, this say, is What is
so mind blowing for me is that, Yeah, I can't

(28:51):
even trust that you, Daniel, sees the same world that
I see. Like, we already know that a lot of
people definitely don't see color in the same way that
others do because there are varying degrees of color blindness.
And it is also hard for me to imagine that

(29:12):
everyone's experience of color is going to be exactly the same,
because of course all of our eyes are going to
be different and our brains are going to be different. So, yeah,
it is. It is really interesting, And there are experiments,
psychological experiments that show that people can differ in like
how many colors they can distinguish between, And I think

(29:34):
it mostly comes down to practice, so like you can
actually practice and become better at distinguishing between different colors. Uh.
And if but if you're unpracticed, something that is a
different color from another thing may look like the same
color to you. I guess that's because a lot of
it's happening sort of in software in your brain, and

(29:56):
so you can improve that by practicing. I love the
way the world looks, you know. I love the purples
and the reds and the blues and all the greens.
And I feel bad if people aren't like experiencing the
same incredible world that I'm enjoying. And then I realized,
hold on a second, maybe everybody else out there has
an even more amazing world, and like the way I'm
experiencing it is like, you know, a thin shadow of

(30:16):
the true beauty of the world. And then I feel
frustrated because we're like all trapped inside our brains that
are painting these worlds for us. Yeah, I mean one
interesting example of how we may not recognize, like we
may think that our way of seeing the world is
the best because we get to see all these pretty colors,
but even when there's an animal that may not have

(30:36):
the same kinds of structures that we do in our
eyes and our brain, they may still have a really
interesting way of perceiving the world we just don't know.
And a great example of this is the octopus. So
octopus is of course we talked about earlier, for having
those incredible chromatophores that not only produce pigment, but can

(30:58):
actually change their shape and can change what kinds of
pigments they produce in order to create this rapid change
in color, and they can use that for things like camouflage.
There's even been there is a guy who kept an
octopus in his living room and he got to watch
this octopus as it was sleeping, and as it was sleeping,

(31:20):
it's it would kind of flicker and its colors would change,
possibly indicating that it was dreaming. And so the octopuses
have these wildly amazing colorful lives, and yet they don't
have color detecting cones, those little photo receptors that are
on our retinas. They only have one type of photoreceptor cell.

(31:44):
And so the thought was, these poor octopuses, they are
so colorful, and yet they can't perceive color because they
don't have cones like humans do. So they might be
producing color on their skins but not observing it any
each other. I always thought that maybe occupied were using
that as a way to communicate, like a visual, colorful language. Well,

(32:07):
octopuses are really interesting because as intelligent as they are
and as spectacular as they are, they're not that social.
They have very limited social interactions. And when they are social,
they do seem to have some changes in their coloration,
but not much is known how they use that for

(32:29):
communication because they're they are very shy, even with each other,
and so their social lives are very limited and we
don't observe them too often. That doesn't mean that they
don't use that coloration to communicate, but it's just so
such a rare event that we have researchers struggle to
actually understand what language they are speaking with this coloration.

(32:53):
But while it may be that they can't see color
because they don't have cones, they may yet be able
to see color because they have a very strange wide
pupil and you've probably seen that it's this like sort
of wobbly wide you shaped pupil, and the this wide

(33:15):
pupil actually scatters light as it enters the eye, which
means that it would hit the back of the eye
the retina at different focal points. So there is a
theory that potentially these octopuses are able to see color
based on the difference of blur and what it sees.

(33:38):
So if it's hitting the eye at these different focal lengths,
for us, we would see that as sort of a
blurry nous Like you know, if you have something really close,
like a hand really close to your face and you
look at it, it's it's blurry. It doesn't look quite right,
or things sort of in the corner of your eyes
are sort of blurred, they're not fully defined. That is
just raw information, right, that we're seeing that as blurry,

(34:01):
and it's our brain's interpretation of that information. But it's
absolutely possible that the octopus is using the difference in
blur results as a result of the different wavelengths of
the colors hitting the eye at different focal points and
interpreting that as color. Wow, that's sort of incredible. What

(34:24):
do you think is sort of the forefront or the
goal of this research. Do we need to like dig
into the octopus brain to understand how it's taking this
information and entangling it and experiencing it. Is it ever
really going to be possible to do science about what,
in the end is sort of a subjective experience. That's
a really good question. I mean, personally, I find octopus

(34:45):
is one of the most fascinating animals in the world
because they have evolved completely, almost completely independently from humans
and mammals and most other animals in the world. Uh,
And yet they have two eyes and a brain, and
they seem to have a certain amount of intelligence that

(35:09):
we can kind of understand. They seem to have a
playfulness of curiosity, and so they're the closest thing we
have to an alien that we can interact with. And
while I don't know other researchers could ever really be
able to fully understand what their subjective experiences, studying these

(35:31):
octopuses and understanding as much as we can about their experience,
I think maybe the closest thing we could get to
studying intelligent alien life and a clue to like what
life might look like on other planets, because their evolutionary
journey was so wildly different from our own in such

(35:53):
a different environment. And of course they're a fun playground
for science fiction authors. I've read many awesome science fiction,
but imagining intelligent octopi or their equivalent from alien world,
it's really fun to think about it into experience. But
it's funny that you call them basically like aliens. I mean,
maybe they would think of themselves as you know, earthlings,

(36:14):
and we are the aliens, right, it's all relative. I mean,
if you've seen there's that document My Octopus Teacher, and
in a way, it really does seem like they see
us as a curious alien because this diver who would
very very carefully and slowly interact with this octopus, the
octopus seemed to take a real curiosity in him. And

(36:37):
there there are a lot of instances of octopus as
being curious about humans, or at least seeming to display
curiosity rather than simply fear, which I find so interesting.
I mean, they are really really mysterious and interesting animals.
And the last time we were related to an octopus

(36:58):
was when everything was basically a tiny nema toad like
worm with just the bare essentials to be able to function,
which I just I find that so interesting and also
kind of encouraging because it makes me think that you know,
given enough evolutionary pressures, it is possible to repeatedly create

(37:21):
organisms that have a curiosity around the world and are
really interesting and maybe are capable of being observers of
their environment, just like humans are. It is amazing that
they evolved their intelligence sort of separately, and it is
hopeful that if independently evolved intelligence finds us curious rather

(37:43):
than like disgusting and squishable, that maybe aliens when they
arrive will also find us worth talking to. I, for one,
would love to hug like a big octopus alien that
would just that would be wonderful. So octopuses are not
the only animals that have a very different subjective experience
when it comes to color. There are a lot of

(38:06):
animals that can see UV light, so ultra violet light,
and so how they pursue the world is going to
be very different from us, and these are There are
a lot of animals, and we're discovering more and more
almost every day who can see UV lights. So butterflies, bees, birds, bats,
and other pollinators can see UV light for pretty obvious reasons,

(38:31):
because flowers have UV light patterns on their petals and
they use these like landing strips for the pollinators to
come like a big eat at Joe's sign neon sign
telling these pollinators, come on, come here, get your nectar.
And while you're at it, why don't you pick up
some pollen and transfer it to my neighbor so we

(38:51):
can get some cross pollination going. I'm glad to see
that kind of interaction facilitated in the natural world. M
And some flowers. Remember we talked about structural coloration, those
like little miniature prisms or slits that will bend light
in certain ways. Some flowers will use structural coloration to

(39:15):
create a blue and UV halo that is typically not
visible to humans but stands out like a hologram two
bees telling them that, like a flower is only tin
wing beats away. So these flowers have cracked holographic advertisement
before humans have, because I was promised when I was

(39:36):
a kid sort of a cyberpunk future where you would
have these holograms advertising soda to you, but that didn't happen.
But these flowers have managed to do that, but we
can't see it. Only bees and other UV light detecting
animals can see those kinds of beautiful displays. Wow. And
bees also basically get jet packs also, so they're living

(39:57):
in the future. And we're stuck here in the present.
That's how do we know? But how do we know
what bees can see? Like if people dissected be eyeballs
to understand what they're sensitive to, or put little recorders
in b brains. It's both, uh, the It's both that
we can see the structure of the b eyeball so
we know UV light can pass through, but also behavioral experiments,

(40:22):
so seeing that bees will go towards UV light when
no other coloration or light is present, that we can
see that they can see these light patterns and they
respond to it. So in an experimental settings, they will
respond to UV light patterns that we we recreate artificially,

(40:42):
so we we can test both their behavior and the
structure of their eyeball to show that it is physically
possible for them to see UV light. You can figure
it out by both combining the behavioral studies with the
anatomical properties of their eyes. What it's like to be
a bee. But what's so interesting is it it makes

(41:05):
sense from an evolutionary standpoint that bees and birds and
even bats can see UV light because they're pollinators. But
research is showing that more and more animals can see
UV light than we may have previously thought. So there's
some evidence that based on the structure of many mammalian lenses,

(41:26):
so that clear uh structure just sitting right on top
of your eye that helps shape the light as it
goes into your eye. Um U V light is able
to make it past that lens and hit the retina,
and so it is likely that their rods and cones
are able to detect UV light and humans. In most humans,

(41:51):
that lens will actually absorb the UV light and so
because it absorbs that UV light, it never actually manages
to hit our photoreceptor cells and so we don't detect it.
But uh. It has also been reported that people who
were either born without a lens or have had their

(42:13):
lens removed for medical reasons, like for cataracts surgery, can
actually see U V light. What how's that possible? Really? Yeah? Yeah,
So there are a variety of surgeries that are done
on the eye to correct for issues things like cataracts.
And so once that lens is removed, it's actually replaced

(42:35):
with an artificial lens again so that you can focus
that light, because without the lens the things would be
too blurry. It helps focus the eye to the back
of your retina, But that artificial lens actually doesn't necessarily
absorb UV light. It can pass through and hit the
retina because it's litting UV light through. It allows people

(42:59):
to both focus saw on an object and also see
u V light, And so people with their lens removed
and replaced will report UV light as looking like this
kind of white violet hue, like a a really oddly
bright violet. And it's one of those things where I

(43:20):
can try to imagine what that's gonna look like, but
you can't really even with a human being, you can
report to you, this is what I see. You can
still only kind of like imagine what that's like. You
can't ever actually experience it. Because they're trying to describe
one color in terms of other colors, but it seems
fundamentally impossible, Like how could you describe red in terms

(43:42):
of blue and green? It's not like some combination of them.
It's like describing something totally different. It's sort of like
you know, eating a new fruit and then describing it like, oh,
it's a little bit like an apple mixed with a kiwi.
It's never going to really capture it right exactly and
it's so it is probably really tricky for people who
see this to be able to describe it, just as

(44:04):
it's hard for us to those of us who cannot
see UV light cannot really imagine what it's like. Uh
so this is this is a fun one. Now. I'm
not an art historian, but there is a historical theory
that Claude Monet's paintings became much more blue and violet

(44:24):
later in life because he had cataract surgery and his
left islands was removed, which allowed him to see UV light.
And so it's possible that he was not just painting
these bright, bright blues and bright violets because he liked
these colors, but because he was actually seeing more and

(44:45):
more of these colors or this UV color that we
can only imagine how it looked like, and trying to
represent it in his paintings. Wow, he wasn't just a genius.
He was an ultra violet genius. It's like extra good.
I want to be an ultra violet physicist. I just
I love. I love how researchers can as we make

(45:10):
scientific discoveries today, it can impact how we see our history,
Like we can see this whole new context for someone
famous like Claude Monet in his life and what he
may have gone through. It is amazing how we can
understand more about what happened in history given our theories now,
Like I don't know if you know the whole story
about the camera, about the camera obscura and how influenced

(45:33):
painting and understanding of like depth and how to paint
depth and painting. It's really fascinating to sort of unravel
that we might understand more than the folks actually at
that time did about what they were doing. Yeah, it
is so interesting. It's like piecing this puzzle together backwards
as human society. And another interesting way that this UV

(45:57):
research can help us understand the world is it may
help us understand our impact on animals. So, um, power
lines typically look pretty boring to us, maybe unless they
explode and like a you know, transformer explodes and then
you you you do get to see an interesting and
very dangerous light show. But two animals that can see

(46:21):
UV light, power lines are horrifying looking all the time.
So the UV light that power lines emit look like
a violet blazing corona. And there is the thought that
this might actually frighten migratory birds who see this don't
know what the heck is going on, and so go

(46:41):
out of their way to avoid these power lines. Uh.
And so there are so many, so many like man
made things that we may see as a somewhat innocuous thing,
but then to an animal it is this terrifying, strange,
alien intrusion, and in their normal lives that is really amazing.

(47:04):
While these birds are basically seeing special effects, and we
of course are always emitting e m radiation in lots
of frequencies that we can't see. You know, radio for example,
in cell communications, these are all electromagnetic radiation. They're basically
just photons of different wavelengths that we can't see. So
if you could see radio waves, if you could see microwaves,

(47:26):
if you could see the frequencies for cell phones, then
the world would look crazy to you around big cities
and be all these intense lights flashing around all of
the time. I wonder if there are animals out there
that can't observe that. So we've talked about how you

(47:49):
can even have color in the natural world through pigmentation,
through structural coloration, through these incredible little microscopic structures that
bend in manpulate light. And we've talked about how other
animals will have these different ways of viewing the world.
Animals who can see UV light, and it just looks

(48:10):
like an entirely different amazing world than what we humans have,
unless humans have some modification done to their eye where
the lens is removed, in which case maybe humans can
see UV light. But now we're going to talk about
how humans can modify animals to make them exhibit amazing

(48:36):
colors and amazing u V glow using things called quantum dots.
So researchers who are always i think, trying to win
award for most science fiction like experiment fed silkworms quantum
dots which cause them to glow red under UV light.

(48:59):
And these quantum dots are nanoscale crystals and are subject
to quantum effects, and the size of the particle can
determine which wavelength of light it will emit. And at
this point I'm going to hand things over to you, Daniel,
because I am sure you can give a much better

(49:20):
explanation of quantum dots than I could hope to do
unless I just open up Wikipedia and start reading it. Well,
first of all, I want to advise your listeners not
to eat a spoonful of quantum dots. Really not a
great idea, and I feel bad for those poor worms,
you know, subjectly to that experiment, but I hope they've
got some awesome superpowers. Quantum dots really are awesome. They're

(49:43):
sort of like an engineered atom. You know, you were
talking earlier about pigments and why some of them are
blue and some of them are red, and microscopically, that's
because the atoms that make up those pigments have quantized
energy levels. The electrons that are whizzing around the nuclei.
They can't just have an the arbitrary energy. There's like
a ladder of allowed energies, and when the electron goes

(50:04):
down one step, it gives off that much energy in
terms of a photon. So the spacing of that ladder
determines the photons that an atom can emit, and that's
why some emit blue and some emit red. That's really awesome,
But it would be cool to like engineer your own
to say, oh, I want this specific set of ladder,
so I get these colors. I want this ladder so
I get those colors. It's pretty hard to do with

(50:26):
atoms because they're kind of finicky and tiny and annoying,
and you need like magnetic fields and lasers and weird
vacuum chambers to manipulate them. So people have figured out
a way to sort of engineer different energy levels using
quantum dots, which, as you say, are basically tiny little
crystals of semiconductors. So my conductors sit right between an

(50:48):
insulator that doesn't conduct electricity and a conductor or like
a metal where electrons just flow free, and so electrons
sort of flow free, and if you make them small enough,
then they get weird quantum effects. Quantum effects usually come
from confinement, from requiring an electron to be like bound
to an atom or stuck in a little hole somewhere.

(51:08):
And so they can like put ingredients in this solution
and heat them up and then have them form these
tiny little micro crystals that can do sort of amazing things,
And there's potentially really incredible, like science fiction like applications
for these things, you know, incredible displays or solar cells
or super tiny electronics. You know, printing like with a

(51:29):
laser printer, um printing like with a laser printer, electronic
circuits made out of quantum dots. It's going to be
pretty awesome. That all sounds cool, But what if we
feed these to a bunch of larvae. Well, I suggest
that you get the larvae to sign off first, you know,
sign the way their rights so they don't sue you

(51:49):
when they start to glow weird colors. I've never seen
a larvae try to hold a pencil, but I'm sure
it's it's pretty adorable and awkward. And you might have
seen quantum dots in real life because they're all already
in televisions Like quantum dot televisions have been around since
two thousand fifteen. Wow, I mean my TV is pretty cheap,
so I kind of doubt it. But that is really

(52:11):
really cool. So when these quantum dots, so the ones
that are fed to these silkworms are like six nanometers,
which I guess is the magic size for the red
emitting quantum dots. They're hit with UV light and this
will cause them to glow red. Now why why do
you need that UV light to see that red glow? So,

(52:34):
just like with any sort of material, you can absorb
it some frequencies and emit it some frequencies, and some
materials like to emit in different frequencies than they absorb,
so they take an energy and then they sort of
like down shifted to a lower wavelength and then emit.
So I don't know the details here, but I'm imagining
that's what's happening that they sort of but I'm imagining

(52:54):
that's what's happening. They sort of wavelength down shifting, So
you send in UV photons, which are very high energy,
and then it bounces around inside the material for a
little while and then emits as a red photon. Yeah,
and that would actually be the same or similar mechanism
as biofluorescence, where you can hit an living organism with

(53:16):
some UV light and they fluoresce under that UV light,
which is different from bioluminescence because the bioluminescence it's actually
a light created by a chemical reaction that produces light,
whereas with biofluorescence, they're actually taking in UV light and
re emitting it at a different sort of energy level.

(53:36):
Which it sounds like that's sort of what's happening with
these quantum dots. And now I'm terrified that your listeners
are going to take laser pointers and shoot them at
all sorts of creators hoping that they'll glow crazy colors.
Please don't do that. People don't do that. But also
that is what researchers are doing. They're collecting like roadkill
of variety of animals, and just whenever they find a specimen,

(53:58):
they like try to see if it glows under UV light,
because they keep discovering all these different animals, especially marsupials
for some strange reason, actually glow under UV light and
we don't know why, and so it is that is
you joke, but there are researchers doing exactly that, Like
they'll find a dead specimen and just sort of see

(54:21):
if it glows. Well, what a job, corpses with lasers
and see what happens? I collect road kill and bring
it back to my laboratory. Yeah, it's it is really interesting.
And so we're essentially turning these silkworms into biofluorescent animals,

(54:42):
except that we are, they're sort of artificially biofluorescence. So
by being fed these quantum dots that glow red under
UV light, not only did the silkworms glow red, but
so did their silk, their cocoons, and the adult moth
bodies after metamorphosis, so they really are what they eat,

(55:05):
like they eat quantum dots, and so their whole world
becomes quantum dots and they retain that. And because the
silk is probably is made out of you know, the
food that they eat and expressed and turned into silk,
of course the silk then is going to also glow red,
and so will their cocoons. And after they go through metamorphosis,

(55:28):
their adult bodies glowed red and even their eggs were fluorescent.
But it finally ended with the second generations of silkworms born,
they no longer glowed. Uh so it only lasted for
the initial silkworms lifespan. But the fact that it was

(55:49):
able to produce all of these effects be retained in
its silk and its cocoon after metamorphosis, it is pretty interesting.
It's a very pervasive way to just by feeding this
animal without actually tampering with its genetics, directly turning it
into a biofluorescent animal. That's pretty awesome. And it makes

(56:10):
quantum silk out of which you can leave like quantum shirts.
That sounds pretty cool. You know, people put quantum and
everything in these days, but in this case, it might
actually be justified. Now you mentioned that you typically don't
want to eat these quantum dots. Now why is that?
Oh man, these quantum dots are made out of crazy stuff.
You know, the kind of materials you need to make

(56:31):
semiconductors can be like weird heavy metals, you know, germanium
and all sorts of craziest stuff. You definitely do not
want to be consuming these things. Yeah, I think that
in this case, for these silkworms, I believe I read
they derived it from some material that was similar to
the mulberry leaves that they would eat naturally. So I

(56:52):
don't think it was hurting these uh, these silkworms. But yeah,
don't like go down to your nearest hard where a store,
pick up some quantum dots and just chug them, because
that's not going to be that's not going to be great.
Ask you a doctor before eating cadmium. But I do.
I I again, I feel somewhat like these these invertebrates

(57:16):
are getting to live cyberpunk future whereas we are not.
Because I was thinking as a kid, you know, you
would get dippin dots, and so quantum dots sound like
a more advanced version of dippin dots where maybe maybe
you could have glowing ice cream of the future. And
I wanted holograms, but only bees and silkworm get get

(57:38):
these futuristic fun treatments. I don't know, I'm imagining quantum
ice cream. Quantum ice cream dots is like a bowl
full of glowing worms or something. It doesn't sound bad
appealing to me. I'm pretty happy with old fashioned ice cream.
I don't think we need to upgrade it to quantum
ice cream. That doesn't sound like the words of a
particle physicist to me. You know, it's all about work

(58:03):
life balance, old fashioned, old fashioned dinner and newfangled and
newfangled work times, splitting particles at work and having a
banana split at home. You go exactly, So before we go,
I know, this whole episode has been about a feast
for the eyes, but now we are going to have

(58:27):
a little dessert for the ears because we're gonna play
a game of guess who's squawking the Mystery animal sound game.
So every week I play a mystery animal sound and
you the listener, and you the guests, try to guess
who is making that sound, and sometimes the answer is surprising.

(58:51):
So the hint last week was this isn't a cat,
it's not a dog, and despite that smell, it's not
a skunk. So, Daniel, can you guess who is making
that sound? M Well, it didn't sound very happy, so
I'm gonna guess some sort of rodent, maybe a squirrel

(59:14):
being force fed quantum dots by a researcher that's not
very caring about their feelings. You know, there are actually
certain flying squirrels that will glow under UV light just naturally.
They weren't force fed any quantum dots. But no, you're incorrect.
This is not a rodent. It is actually a fox.

(59:38):
This is one of the many sounds that a fox makes.
This fox in particular is sort of sleepy, sort of
relaxed and issuing a gentle little call just to kind
of say hello to one of its fox friends that
is nearby. Oh it's a cozy, snuggling fox. It's a

(01:00:00):
cozy little fox. Yes, Oh, I'm glad. It's a happy sound.
Maybe it's cozy because it just ate one of those
quantum glowing squirrels. I don't know, but yes it is.
It is a relaxed sound from a fox. Foxes have
a wide variety of calls to express themselves, from mating
calls to alarm calls, to fighting cackles or play laughter,

(01:00:25):
and even these pearl like sounds they can make when
they're comfortable, or these little like murmurs that are sort
of like, hey, I'm over here, how are you doing?
Kind of sounds. As far as I can tell now,
I don't speak fluent fox, so something may have gotten
lost in translation. As adorable as foxes are and the

(01:00:46):
sounds they make, they are terrible pets and unless you
are prepared for an undomesticated, incredibly stinky, hyperactive beast, they
are extremely smelly, which often surprises people because you know,
we think of a skunk now that makes a bad smell,

(01:01:07):
But foxes are really smelly and not eat They won't
even just kind of like spray you in self defense.
They are smelly almost all the time because they have
a number of scent glands, both on their tails or
near their anus, on their feet and under their chins,
and these scent glands will excrete a musk, which is

(01:01:32):
basically a calling card for the foxes, like leaving a
little business card in the form of a real stinky smell,
and their feces and urine is also riddled with this musk,
so their urine in particular is extremely foul smelling. I
would never recommend a fox as a pet. Typically, pet

(01:01:54):
foxes are only tamed, which means that they are not
They have not been genetically my defied to be more
calm in our presence. They have just been raised since
they were a pup to basically tolerate humans. But yes,
I just I think the stinkiness alone should be enough

(01:02:15):
to ward people off from owning foxes as pets. Wow,
well you just wow, Well you just answered too deep
philosophical questions. They're not just the age old question of
what does the fox say? But also how does the
fox stink? Pretty badly? Smells pretty bad. I mean they

(01:02:35):
have a good sense of smell, but a bad sense
of taste because of how bad they smell. So onto
this week's mystery animal sound and the hint is is
it a helicopter, a jackhammer, a lawn more or something
from Greek mythology? Daniel, who do you think is squawking? There?

(01:03:02):
It sounds to me like fluttering of wings. Is it
like maybe a super close up microphone to a bee's wings.
That's an interesting guest. Well, you will find out if
you're correct on next week's episode of Creature Feature next Wednesday.
If you out there think you know who was squawking,

(01:03:22):
you can write to me a Creature Feature Pod at
gmail dot com. I'm also on Twitter at Creature Feet Pod.
That's feteeth. How does something very different? Daniel, thank you
so much for joining me today. This was a wonderful
mixture of both biology and physics resulting in a beautiful

(01:03:43):
rainbow of amazing animals. Where can people find you are?
You can find me at our podcast Daniel and Jorge
Explain the Universe on Twitter at Daniel and Jorge or
online at www dot Daniel and Jorge dot com. Come
on over and talk about the physics of the universe
with us, and I am sometimes on the show when

(01:04:05):
Jorge has to step out, or as some people theorize,
we're simply the same person feed enough quantum dots of
Jorge and becomes a biologist named Pete. Thank you guys
so much for listening. If you're enjoying the show and
you leave a rating and review, I would be so
very grateful, And I read all the reviews, even the

(01:04:29):
reviews saying like, hey, I want to eat quantum dots,
and then I would say, hey, don't do that. Uh
if I could respond to the reviews, but I still
appreciate them and thank you to these space Costlics for
their super awesome song. Exo Alumina Creature features a production
of I Heart Radio. For more podcasts like the one

(01:04:50):
you Just heard, visit the I Heard Radio app Apple podcast,
or Hey guess what whereever you listen to your favorite shows,
I don't. I don't judge you. I do judge you
if you eat quantum dots, but I won't judge you
for where you listen to your podcasts. See you next Wednesday.
M