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CHERYL HAYASHI: When I started working on spiders,
I had no idea how interesting they were.
I had no idea.
I mean, these organisms have been making silk
for hundreds of millions of years,
and they're all using silk in a slightly different way.
We're still finding new kinds of silk all the time.
So, when you see an orb web, I guarantee
you don't know the whole picture.
And it's only when you get up close that you
realize how cool they are.
I'm Cheryl Hayashi.
I'm a curator at the American Museum of Natural History.
And I study the evolution of spiders and spider silk.
In my research, I'm characterizing the diversity
of spider silks, and I do this to understand how silk evolved,
how it works, and what it means to spiders.
And that's what keeps me up, just
these fundamental questions.
So, spiders are the only animals that
really rely on silk throughout their entire life, sort
of every part.
To eat, to reproduce, to wrap eggs, to transfer sperm.
They make their homes out of silk,
but some species don't use silk as much as others.
I mean, they still will use silk almost every day of their life,
but they may not rely on silk for foraging.
While other spiders like orb web weaving spiders
are absolutely tied to silk production,
and they use those silks for all kinds of purposes.
If you look inside the abdomen, it's packed with silk glands.
It's not as if there's spools of thread.
It's actually liquid silk stored inside the silk glands.
So, the liquid silk goes through the duct.
It dehydrates, and the silk proteins
start aggregating with each other.
So, when you see a spider dropping down,
you're actually watching, in real time,
liquid silk being turned into a solid fiber.
It's an amazing transformation.
What just really captivated me about spiders
was the diversity of silk that one individual spider can make.
Picture in orb web.
There'll be an outer frame and there
will be radii from a center point that go out.
So that kind of silk is made from drag line silk,
or we call it major ampullate silk.
That's a strong and fairly extensible silk.
Then there's the capture spiral.
That's a composite of two kinds of silk.
There's a filament dotted with glue on it.
But in making the orb web, the spider
will have used a so-called minor ampullate
silk or temporary silk.
Then she actually uses that temporary spiral
as a guide as she lays down the real capture spiral.
And while she's doing it, she consumes the temporary spiral.
When you think about why a spider might
make so many different kinds of silk,
it really comes out to function.
The frame and the radii need to be stiff to support the web.
But if a web was made entirely of strong and stiff fibers,
it might be a lot easier for an insect
to just bounce off of it.
So capture spiral silk stretch along,
absorbing the impact of that insect.
And the little gluey, gluey droplets
stick to the insects' body, and it holds the insect in place
and gives the spider time to come down and actually catch
their prey.
So, whether we're talking about egg case silk, drag line
silk, capture spiral silk, or prey wrapping silk,
they all have different functions,
and they all have different material properties.
Spiders that make multiple kinds of silk.
they actually, they have multiple types of silk glands.
And so, when it's time to make a web,
the spider is actually touching her leg to the correct spigot
to pull out the correct silk in the correct place
on the web at the correct time.
So, I want to find out exactly what genes
are turned on in all those different silk
glands within a spider.
So for that, I need to have fresh silk glands.
And so, I have a lot of live spiders in the lab
so I can collect their silk and collect their silk glands.
I have a variety of garden spiders.
I have golden orb weavers.
I also have black widows, and I also
have feather-legged spiders.
I collect silk from spiders in two different ways.
I take these little cards that I make out of poster board,
and I collect fibers onto that card.
The other way I collect silk in the lab
is I expose a spider to carbon dioxide gas,
and that anesthetizes them for a few minutes.
And I gently tape them to the microscope stage
so I can actually visualize which
spigot a silk fiber is coming out of
so then I know exactly what silk I'm collecting.
And when I'm done, they live to silk another day.
After I've collected the silk, the way I test the fibers is,
I put it in what's called the tensile tester.
And the machine pulls up at a controlled rate.
And as it pulls up, it's measuring the resistance
of the fiber to being pulled, and it's also measuring
how far the fiber can stretch.
And with that, I can really compare a large number
of different kinds of silks.
The silk protein genes are activated in the silk glands.
Each gene, we're finding that they might be dramatically
different from each other.
That leads to dramatically different
mechanical properties.
So, in the capture spiral, it can extend over
twice its original length.
There's not that many filaments that can do that.
Many drag lines silks are tougher
than Kevlar, which is just amazing thinking
of that within a spider just out in your yard.
And these super fibers are coming out of it.
And when you look at the whole diversity of spiders,
there's just an immense variations on this.
So, the honest truth is, it's almost
like my research is becoming fractal.
What I thought was one silk turns out to be two silks.
What I thought was going to be one silk gene
turns out to be sometimes five silk genes.
In a sense, I have gotten trapped in a spider web.
And the silk envelops sort of all aspects of my research,
but I'm not fully trapped, because I think the spider silk
system, it's a great model for seeing
how you can integrate evolutionary biology, genetics,
organismal biology.
Even, let's say, you're interested
from the biotech aspect of it.
There's just huge potential there.
There are lots of research being done into how we can mass
produce silk, either to make better clothing, maybe lighter
airplane or car parts, or implants that could
be used in the human body.
And so, spider silk, it's coming to your world.
LUKE GROSKIN: Hey there.
This is Luke Groskin, video producer for Science Friday.
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