Kind: captions
Language: en
you are not looking at a yellow ball
your brain might think you're looking at
a yellow Ball but look closer the screen
you're watching this on displays color
using only red green and blue sub pixels
the yellow your brain thinks it's seeing
is actually a mix of red and green light
the camera I'm talking to right now has
a sensor composed of red green and blue
sensitive photo sites again no yellow of
course I have the ball here in my hand
so I am looking at a yellow ball or am
I after all my eyes aren't so different
from that camera the human retina only
has cone cells sensitive to red green or
blue wavelengths of light to perceive
other colors we have to integrate the
inputs from those three cone types when
yellow light enters my eye it stimulates
my red and green sensitive cone cells
although not as much as pure red or
green light would with red and green
sensitive cones equally excited my brain
tells me I'm looking at yellow this is
how our technology our cameras and
screens and projectors can trick our
brains into seeing a whole rainbow of
colors using just three wavelengths of
Light by triggering our three different
types of cone cells in different
proportions so is the ball really yellow
what does yellow even mean a lot of
people would say that color is the
wavelengths of light that an object
reflects in other words like Aristotle
thought color is a property of the
object but looking at the same ball on a
screen Your Eyes Only sensed red and
green light yet your brain still
perceived it as yellow so it's also
possible like Galileo believed that
color isn't a property of an object at
all but a phenomenon of the Mind
instead but whose mind because we aren't
the only animals that can see the world
in
we often times don't really think about
how other animals see color so for
example we buy our dogs bright red or
orange toys that are only bright red or
orange for us and not for them because
they can't see orange or red as being
distinct from Green so maybe we should
start taking in the world from more than
just the human perspective doing that
might just teach us why color vision
evolved in the first
place we're actually towards the lower
end of the spectrum honestly we're a
step up from our household pets maybe if
they're cats or dogs but not nearly as
good as many animal groups out there
butterflies Birds fish lizards jumping
spiders jumping spiders are harmless
creatures actually they don't ever
really get big enough to pose much of a
threat to humans of course if you were a
small insect yes you would absolutely
need to be afraid of a jumping spider
they'll take down prey that's sometimes
like two or three times their own body
size the Chinese word for for jumping
spider translates literally to fly tiger
and that's the way I like to think about
them is the kind of small cats of the
undergrowth jumping spiders are
everywhere um they're in your backyard
they're probably in your kitchen there
are about 6,000 species of jumping
spiders known some are sort of furry
some are sort of shiny striped spotted
red green blue pretty much anything you
can imagine it's like everyone is a
little work of art as a group spiders
aren't know known for their Vision I
mean most species are nocturnal and for
many their webs act as a sort of extra
sense organ so they just don't need to
see that
well but jumping spiders as active
daytime Hunters well they're different
not only do they have great eyesight but
different species have different forms
of color vision look at those
eyes jumping spider eyes are fascinating
and when I say eyes I mean eight eyes
jump spiders split up things like motion
detection and light sensitivity to some
eyes and then color vision and fine
detail Vision into others the pair of
eyes that are perhaps the most
fascinating or most unusual are what we
call the principal eyes and those are
the really big eyes in the front of the
face that make jumping spiders look a
little cute if you're willing to say a
spider looks cute ever and those are
built unlike any other eye in the animal
kingdom it turns out the way jumping
spiders perceive color has everything to
do with the anatomy of those principal
eyes they're really actually built a lot
like a gan telescope or binoculars that
big lens that you see from the outside
of the animal is one of two lenses in
these eyes and in between those two
lenses is a long fluid filed tube at the
end of that fluid fil tube is a second
lens and what that lens does is it
magnifies the image that that first lens
projects down that long tube and in that
way it increases the ability to see
detail by the retina that sits right
below it and when it comes to seeing
detail it's hard to beat a jumping
spider for most animals the bigger the
eye the better it functions jumping
spiders absolutely break this rule the
secondary eyes can see the world about
as well as the absolute best insect eyes
out there better than the world's
biggest dragon flies whose entire head
is consumed by an eye the principal eyes
they can actually see pattern in the
world better than a lap dog a house cat
an elephant and nearly as good as the
sharp-sighted
pigeon but it's a very narrow slice of
the world that they can see it's about
like your thumb held at arms length and
it's only in that narrow slice of the
world that jumping spiders can see fine
detail and
color so the jumping spider secondary
eyes give them a full
360° view of the world now imagine most
of that's in black and white when you
see something move you can swivel to to
look at it and now anything that's
really of curiosity to you you can add
to this world of black and white Vision
fine detail and color but you can only
do it Moment by moment so you're really
kind of painting additional details
about color and pattern that you
couldn't see
otherwise it's a wild world to try to
put yourself
into as they sweep their principal eyes
across a scene some species of jumping
spiders are adding a lot more color
information to their world than
others most jumping spiders including
this one are d chromates meaning they
have two types of color sensitive cone
cells in their retinas just like dogs
and most other mammals and by comparing
those two kinds of cells and how they
respond to light in the environment they
get a coarse understanding of color they
can tell the difference between UV
violet blue and green but some types of
jumping spiders are trir chromates with
three types of cones like humans and
others are tetrachromats like
birds the weird thing is all these
species with expanded color vision
aren't necessarily close relatives in
jumping spiders we have huge variation
uh even from closely related groups and
how well they're able to see color in
the world jumping spiders are
Reinventing in some ways the ability to
see color over and over again in
different ways that makes jumping
spiders pretty special I mean consider
primates oldw World monkeys apes and
humans all have TR chromatic color
vision but we also share a common
ancestor so our color vision probably
evolved only once and then it stuck
around this is where jumping spiders
really stand out the ability to see red
for example has evolved several times in
jumping spiders researchers know that
because they've figured out how
different groups are related and by they
I mostly mean jumping spider fanatic
Wayne
Madison oh my Gosha
fantastic beautiful
male oh it's been it's been 30 years
since I've seen aive Hava he is
absolutely Mr jumping spider his um
expertise really is in jumping spider
taxonomy I work on the evolutionary tree
of jumping spiders The evolutionary tree
of life is basically the pathway of
genetic descent that links all of us the
position of different species on this
evolutionary tree can tell us how they
ended up with the traits they have like
if most jumping spiders don't see red
but two species on two very different
parts of the tree do chances are that
those two species evolved those
abilities
independently in which case then we can
start to ask questions like and what's
driving that Evolution do they have
similar ecologies do they hunt similar
prey and try to really understand what
selective forces are leading to these
expanded color vision systems it might
help them find food or discriminate
tasty prey from prey that can harm them
because of course lots of small insects
are brightly colored and some of them
are using those bright colors to
advertise that they're
toxic another possibility is that seeing
a richer World of Color might help
animals from lizards to spiders choose
better
mates to test these ideas the
researchers needed to know which of the
6,000 species of jumping spiders had
expanded color vision and which didn't
and outside of a few well studied
species no one really knew so the team
set out to collect spiders from every
major branch of the jumping spider
family
tree one of our first things is just
prioritizing where to go and what to
look for and so it's a lot of sampling
in a lot of places let's see who lives
here it's kind of like Pokémon go except
the Pokémon are real they're smaller
than your pinky fingernail and they're
really good at
hiding some jumping spiders have evolved
to be really fine-tuned to a particular
situation so for example there are
termite eating specialist jumping
spiders that you're only going to find
around termites there was this one
species that we only found in piles of
bones in South Africa who knows what it
was doing there but we quickly learned
that that was the only place in the
environment we were going to find it and
so that's part of the fun of it I feel
like it's a bit of a treasure hunt
really with no proverbial Stone left
unturned the team returns to their Labs
with hundreds of spiders representing
many different species they want to
figure out which species have expanded
color vision how each species does it
and why it's actually a hard question to
tell how animals can see color we can
just connect our brains to see what they
see so how do we do
it we begin by using a technique called
microspectra photometry it's a really
long word what it simply means is a
microscope paired with a device that
measures different wavelengths of light
a
spectrophotometer the researchers take
ultra thin slices of jumping spider
retinas then they measure the
wavelengths of light absorbed by
individual cone cells
with enough of these measurements they
can tell if a species is a DI chromat TR
chromat or tetrachromat and what
wavelengths of light its cells are best
at
detecting but that's not the whole
story having that knowledge of what's in
the retina tells us what is or isn't
possible for these animals to see but it
doesn't actually tell us what they do
see or how they might use that and so
the gold standard for establishing that
an animal can see color is to do so
behaviorally in other words we somehow
need to ask the spiders what they can
see and then understand their answers
figuring out what's going on inside a
spider's mind is difficult it's no
surprise that it takes a group of expert
zoologists to do so but our own minds
can be just as complicated yet we rarely
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jumping spiders and how they see color
these animals are particularly motivated
to investigate things that move and
these responses can be guided by color
the theory is simple you show the spider
a screen with a moving shape that
differs from the background in color but
not in brightness and you see if the
spider tries to follow the problem with
letting the jumping spider actually turn
and respond is that they'll absolutely
do so but it changes some of what they
see
so what we want is to really have some
control over what the spiders can see at
any given moment so the researchers hold
them in place with tiny magnets attached
to their heads what we do is we give
them a ball to stand on they actually
hold it with their feet and we can
monitor how that ball moves around in
their feet to know where they would want
to go if the spider turns the ball to
the left it's probably trying to look
look to the right to follow the moving
shape and that's evidence the spider can
discriminate between the colors of the
shape and the
[Music]
background once the team knows which
species can see which colors the next
question is how do they do it what's
different in the DNA of these spiders
that can see and discriminate more
colors if you ask Megan Porter a lot of
it comes down to genes that encode
proteins called opsins
the way that animals achieve color
vision is to have different copies of
this opson Gene and those variations
then are what produce proteins that are
sensitive to different colors of
light the first uh technique that we
generally go to with a new species is
called transcriptome sequencing and this
is where we can take the entire head of
a jumping spider and we can get the
sequences for every single Gene that is
expressed in in that tissue this method
gives the researchers an inventory of
all the genes being expressed in other
words all the genes that are copied out
of the DNA and sent to make a protein
then the team can figure out where each
of these genes is expressed in which
eyes and in which parts of the eye and
we do that using a fancy technique
called imunohistochemistry the
researchers basically create glowing
molecular tags specific to each protein
they're interested in and then looking
for which parts glow in the right color
we can figure out where each opson is
being expressed where the protein is
located the team is especially
interested in genes that are expressed
in the retinas of the principal eyes
these are the genes most likely to be
related to changes in color
vision already this process of asking
which species have expanded color vision
and how they accomplish it has led to
some surprising discoveries the
researchers already knew that the
ability to see and discriminate more
colors had evolved more than once among
jumping spiders but they hadn't realized
just how widespread this ability would
be after measuring 45 species Across The
evolutionary tree the team has already
found as many as 12 independent changes
in color vision in evolutionary terms
jumping spiders seem to be evolving new
expanded forms of color vision all the
time and different species have acquired
their new visual capabilities in very
different ways take for example the
ability to see red most jumping spiders
only have green sensitive and UV
sensitive photo pigments in their
retinas but some species became
sensitive to red when their green
sensitive opson Gene was accidentally
duplicated in the genome and the new
copy started to evolve shifting its
sensitivity to longer
wavelengths so in our eyes that's
exactly what happened the opson gene for
our green sensitive visual pigment was
duplicated and the second version
evolved to be more red sensitive and we
see this happen over and over and over
again in jumping spiders but other
jumping spiders see red in a totally
different way rather than evolving new
photo pigments they added an internal
filter to some of their green sensitive
cone cells which cuts out green light
and forces those cells to respond only
to longer wavelengths like red they can
basically create two kinds of cells from
the same type of photo receptor simply
by using a filter in front of some of
them and not in front of
others all this evolutionary Innovation
makes the original question even more
intriguing why evolve expanded color
vision in the first place that's the
question Lisa Taylor is trying to answer
for a visual Predator like a jumping
spider better color vision could mean
finding more prey it could also mean
avoiding prey that might be harmful and
so a lot of prey in the environment um
advertise their toxicity with bright
colors and particularly with long
wavelength colors such as red and orange
so we're testing the idea that the
ability to use color vision will help
these spiders learn to avoid and
continue to avoid red prey that tastes
bad in this experiment all the prey are
termites some have a dab of red paint on
their backs and others have a dab of
gray and this doesn't affect protect
their behavior in any way they still
move around naturally and the spiders
really like to eat termites the red
termites also get treated with a
compound called bitrex which is actually
the most bitter substance
known and um yeah it turns out that the
spiders also think it tastes disgusting
so we can simultaneously and
independently manipulate color and
palatability in other words the
researchers can make the termites red
and bitter gray and tasty or if they
want to mess with the spider
gray and bitter or red and
tasty the first part of the experiment
is the training phase basically the
spiders get to choose from a tiny Buffet
of termite prey each one in its own
little petri dish in three of the Petri
dishes they get a red painted bitter
tasting termite and then the other three
Petri dishes they get a gray painted
very tasty
termite as they interact with this prey
they they um are constantly learning and
it's constantly being reinforced that
whenever attack something red they get a
a mouthful of bitter tasting termite and
whenever they attack something gray they
get a mouthful of of tasty termite the
first spiders to go through this
experiment are Hiatus pyri and we
started with them because we know that
they have um they have good color vision
that extends into the long wavelengths
Hiatus pyric is one of the species that
can see red using a red filter in front
of some of its green sensitive cone
cells our data so far suggests that the
spiders are really good at learning the
rules
and once they learn the rules then the
real experiment Begins the spiders hunt
for all their food in a setup just like
the termite Buffet where they were
trained except that for half of the
spiders there's a big difference some of
the termites are still bitter but
they're all gray the color cues are
gone now the question becomes do the
spiders that have color cues available
in other words the ones for which bitter
termites are still red do they do
better so our data so far show that they
they do Faire better when they have
access to those color cues they lay eggs
sooner and that they're also heavier at
the end of the experiment if they're in
the treatment group where they have
access to color cues one hypothesis for
why primates evolved expanded color
vision is to distinguish ripe from
unripe fruit or Tender new leaves from
older tougher ones in other words
telling good food apart from bad food
kind of like what these spiders are
doing
here we've got this kind of evidence in
a jumping spider and um we're going to
repeatedly test that in other jumping
spider species that have different forms
of color vision the team predicts that
spiders with expanded color vision will
use color cues to their advantage so
they'll do better when color can tell
them which prey items taste bad species
that can't see red won't get any benefit
from the warning colors or from the
training if the data support these
predictions the these will be some of
the first experiments in any species to
reveal an evolutionary advantage to
seeing and discriminating more
colors but feeding Behavior can't be the
whole story because the spiders had some
more surprises in store for example
There's A genus of jumping spiders in
Central America called mexon where males
and only males sport incredibly bright
red colors on parts of their body that
they use during courtship we thought for
sure the female has got to be paying
attention to Red distinguishing it from
other colors they've got to have uh red
color vision in some special way and it
turns out that at least by our
measurements they don't have the ability
to see red they just have UV and green
sensitive cells in those principal eye
retinas I don't mind being proved wrong
at all it usually means something more
exciting because it means that oh my God
there's something cool and new in the
world right and you've learned something
new
so what's going on here to help answer
that question and maybe understand why
some spiders are displaying to one
another with colors they can't see it's
time to revisit the jumping spider
retina instead of just one retina like
we have they have a stack of translucent
retinas right on top of each other one
thing that we think that this layering
does is to correct for a problem that
the Optics present to the retina it's
called chromatic aberration
most Optical materials like these glass
prisms refract or bend short wavelength
light like blue and UV more strongly
than long wavelength light like red
that's chromatic aberration lenses do
this too in photos taken with vintage
camera lenses you can often see a fringe
of color around high contrast edges the
sensor in a camera is a single flat
layer of photo sites so getting the
different colors of light to focus in
the same plane is critical modern camera
lenses correct for chromatic aberration
using complicated Optical designs with
lots of lens elements but the other
solution is to put different color
sensitive cells at the right depths
behind the lenses so that the colors
that they're sensitive to are in proper
Focus that's exactly what jumping spider
re is due and this gets us one step
closer to understanding what red might
mean to a spider that can't actually see
red in the jumping spider eye the cells
sensitive to Shorter wavelengths are
generally closer to the lens and those
sensitive to longer wavelengths are
farther away but most jumping spiders
are die chromates they only have two
cone cell types so why have four layers
in their retinas typically the bottom or
farthest away from the lens two tiers we
call those tiers one and two
those are both typically sensitive just
to green light and with a retina like
that an object in that world might
appear in different focus in tier 2 than
in tier one researchers in Japan have
shown that jumping spiders can actually
use this discrepancy in focus to
perceive depth and distance in their
environment but there is a liability
with this system it only works if you're
just using one color of light like green
if you start to mix in other colors of
light for example red then the system
creates errors essentially colors like
red might create this perception of
being close or being looming towards the
receiver and that would provide a
totally different perceptual experience
for the
viewer so a jumping spider's red
coloration might not look red to another
jumping spider but instead create a sort
of depth illusion but why would a male
spider benefit from displaying an
optical
illusion one thing about jumping spiders
is that females often are quite
aggressive towards prospective mates in
fact they can often eat the male rather
than allowing him to mate with them so
these males when they're dancing for
females are are really actually dancing
for their lives in many
instances if a female thinks a male is
closer than he really is that could
throw off her attack or maybe confusing
the female pays off in other ways if she
can't quite figure out the male's
display she might stick around paying
attention to it for longer and this
might result in better outcomes for the
male at the end of
courtship and Amorous male spiders might
not be the only ones exploiting these
depth
Illusions so imagine a red prey item we
might look at it and say that's probably
toxic and it's warning birds that is
toxic but another possibility is that
it's red simply to look like it's closer
to a jumping spider so that it has a
better chance of escaping we also see
small insects with red and blue patterns
on them which would create a really
complicated visual illusion that might
simply baffle it and require it a longer
period of time before it judges this
distance even a split second can really
matter but in this tiny game of cat and
house a spider that could see and
discriminate red from Green would be a
lot harder to fool and this could be
another surprising benefit of color
vision one that isn't really about color
at
all and what we really need to ask
whether not this hypothesis is even
plausible is really good
highresolution measurements of the
distances of things in their eyes
including the retina and the lenses from
live animals this information you can't
just get from preserved specimens on
microscope slides but there is another
way by using a particle accelerator
called the advanced Photon Source the
researchers have started to collect
highresolution X-Ray videos through the
spider exoskeletons this has never been
done before it's in x-ray so we can see
through their eyes and we can see how
these eye tubes are moving
around if the spider's retinal movements
change the shape or length of their ey
tubes that'll affect what they're
capable of perceiving it would change
how they experience depth it would
change how they experience color
previously this information has only
been collected from dissections so we're
very excited to get uh super high
resolution videos of the inside of the
spider's head as it's performing
complicated visual motions unfortunately
a few months after their initial tests
the advanced Photon Source shut down for
upgrades that'll take over a year to
complete
so it looks like we'll have to wait a
little longer for some of the answers
the team has been looking
for we know that the redness can be
moved around and that they maybe have
between a 50 and 60° travel not only can
they be moved in the horizontal plane
but in the vertical plane and they can
actually be twisted to change the
orientation of their field of view the
question is how do these movements
affect what the spiders can focus on or
how they sense depth or even how they
perceive color it's this connection
between Focus depth and color that makes
these spiders so intriguing it opens up
all sorts of questions about what color
is in the first
place it's already clear that these
spiders have a lot to teach us about
color vision how and why it evolves and
how many forms it can take even within a
single group of
animals if our understanding of their
visual system is correct the experience
of color for jumping spiders might even
be three-dimensional in a way that's
totally different from how we see the
world and we haven't even talked about
their other senses like their ability to
communicate through
vibration when you think about it you
realize that the Universe we humans
perceive even with all our technology is
just a sliver of what's out
there if we owe anything thing to the
world it's to allow the world to be
experienced in the fullness of
itself I think this is one of the
tragedies of Extinction is the loss of
often times a totally unique way of
experiencing our world a way of
experiencing our world that we probably
couldn't even
imagine so color what is it is it an
intrinsic property of an object like
Aristotle thought or something that
exists only in the mind perceiving it
like Galileo believed maybe it's not an
either or
question my belief is that color is
something that emerges through the
evolution of the eyes that see the world
and the world that the eyes see color as
a thing emerges through this dance this
evolutionary dance between what can be
sensed about the world and those that
are sensing
it it's that dance playing out over
millions of generations that created the
colorful world we inhabit and shaped the
countless ways that we and our fellow
life forms experience
[Music]
it come to me okay not that
far they're not called jumping spiders
for nothing come on e