WEBVTT

00:00:00.000 --> 00:00:02.620 align:middle line:90%


00:00:02.620 --> 00:00:06.970 align:middle line:84%
So another question we have
just recently been dealing with

00:00:06.970 --> 00:00:09.280 align:middle line:84%
is, do predators and
parasites of herbivores

00:00:09.280 --> 00:00:14.060 align:middle line:84%
influence their feeding
habits and host plant choices?

00:00:14.060 --> 00:00:19.480 align:middle line:84%
And let me just tell
you about Carcelia.

00:00:19.480 --> 00:00:23.260 align:middle line:84%
The main enemy of Estigmene
in Southern Arizona

00:00:23.260 --> 00:00:26.710 align:middle line:90%
is a fly called Carcelia.

00:00:26.710 --> 00:00:29.350 align:middle line:84%
And just like with the
Manduca I told you about,

00:00:29.350 --> 00:00:34.150 align:middle line:84%
this thing lays eggs on the
surface of the caterpillar.

00:00:34.150 --> 00:00:37.360 align:middle line:84%
And when the maggot comes out,
it bores through the cuticle

00:00:37.360 --> 00:00:41.350 align:middle line:84%
and eats out the inside of
the caterpillar and kills it.

00:00:41.350 --> 00:00:45.545 align:middle line:84%
And so it's a pretty
nasty piece of work.

00:00:45.545 --> 00:00:46.045 align:middle line:90%
[LAUGHTER]

00:00:46.045 --> 00:00:51.520 align:middle line:84%
And actually, these
flies are really common.

00:00:51.520 --> 00:00:53.800 align:middle line:84%
And this whole family of
flies is really common.

00:00:53.800 --> 00:00:55.990 align:middle line:84%
When you're out having a
picnic and you think, ooh,

00:00:55.990 --> 00:00:58.540 align:middle line:84%
nasty flies, they're probably
doing a really good job

00:00:58.540 --> 00:01:00.417 align:middle line:90%
killing caterpillars.

00:01:00.417 --> 00:01:03.040 align:middle line:90%


00:01:03.040 --> 00:01:05.830 align:middle line:84%
And this is what happens
to the caterpillar.

00:01:05.830 --> 00:01:08.140 align:middle line:84%
It's totally eaten
out by the maggots.

00:01:08.140 --> 00:01:10.570 align:middle line:84%
And the maggots come out
and make their own pupae.

00:01:10.570 --> 00:01:13.780 align:middle line:84%
And these will become
new flies to infect

00:01:13.780 --> 00:01:17.200 align:middle line:90%
a new lot of caterpillars.

00:01:17.200 --> 00:01:20.830 align:middle line:84%
Well, what we found was that
the parasitized caterpillars

00:01:20.830 --> 00:01:23.590 align:middle line:84%
show an increased
responsiveness to PA

00:01:23.590 --> 00:01:26.320 align:middle line:84%
and decreased
responsiveness to bitter.

00:01:26.320 --> 00:01:29.440 align:middle line:90%
So we tested the sugar cell.

00:01:29.440 --> 00:01:32.500 align:middle line:84%
No change in the unparasitized
and the parasitized.

00:01:32.500 --> 00:01:36.292 align:middle line:84%
Do you mean these are
caterpillars in the process

00:01:36.292 --> 00:01:37.750 align:middle line:84%
of being eaten out
from the inside?

00:01:37.750 --> 00:01:38.250 align:middle line:90%
Yes.

00:01:38.250 --> 00:01:39.970 align:middle line:84%
So we collected a
load of caterpillars

00:01:39.970 --> 00:01:44.410 align:middle line:84%
from the field, tested
their sugar cell, their PA

00:01:44.410 --> 00:01:48.770 align:middle line:84%
cell, and the cell's
response to bitter compounds.

00:01:48.770 --> 00:01:51.430 align:middle line:84%
And then we dissected
them and see

00:01:51.430 --> 00:01:54.640 align:middle line:90%
which ones had maggots in them.

00:01:54.640 --> 00:01:58.540 align:middle line:84%
So the sugar cell wasn't altered
by the presence of maggots

00:01:58.540 --> 00:01:59.320 align:middle line:90%
inside.

00:01:59.320 --> 00:02:00.620 align:middle line:90%
Nope-- no effect.

00:02:00.620 --> 00:02:03.250 align:middle line:84%
But the PA cell, if
they had maggots inside,

00:02:03.250 --> 00:02:05.320 align:middle line:84%
they were much more
sensitive to PAs.

00:02:05.320 --> 00:02:07.090 align:middle line:84%
And the PAs is a
plus cell, remember.

00:02:07.090 --> 00:02:11.080 align:middle line:84%
It's going to make them eat
if they contact the PAs.

00:02:11.080 --> 00:02:16.630 align:middle line:84%
And the presence of maggots
here reduced the sensitivity

00:02:16.630 --> 00:02:20.990 align:middle line:84%
to the bitter compounds,
to the deterrent compounds.

00:02:20.990 --> 00:02:23.350 align:middle line:84%
Now, the PA plants
have PAs of course.

00:02:23.350 --> 00:02:25.240 align:middle line:90%
They've also got deterrents.

00:02:25.240 --> 00:02:28.630 align:middle line:84%
So what this means is that
they'll eat more PA plants

00:02:28.630 --> 00:02:30.880 align:middle line:90%
if they've got parasites.

00:02:30.880 --> 00:02:34.660 align:middle line:84%
And that means they'll
destroy more parasites within.

00:02:34.660 --> 00:02:37.820 align:middle line:84%
So it's a little bit of
a complicated situation.

00:02:37.820 --> 00:02:39.940 align:middle line:84%
But the presence
of the parasites

00:02:39.940 --> 00:02:44.620 align:middle line:84%
makes them behave in a way
that's really adaptive.

00:02:44.620 --> 00:02:45.470 align:middle line:90%
I have a question.

00:02:45.470 --> 00:02:45.970 align:middle line:90%
Yeah?

00:02:45.970 --> 00:02:48.610 align:middle line:84%
Once the parasites
get in, is that it?

00:02:48.610 --> 00:02:49.420 align:middle line:90%
Is it all over?

00:02:49.420 --> 00:02:50.110 align:middle line:90%
No.

00:02:50.110 --> 00:02:51.340 align:middle line:90%
Or can they chase them out?

00:02:51.340 --> 00:02:53.260 align:middle line:84%
Yeah, if they eat
enough PAs, they

00:02:53.260 --> 00:02:55.130 align:middle line:84%
can kill a lot of
those parasites.

00:02:55.130 --> 00:02:57.380 align:middle line:90%
And then they can often survive.

00:02:57.380 --> 00:03:00.190 align:middle line:84%
So in fact, what
we're talking about

00:03:00.190 --> 00:03:04.000 align:middle line:84%
here is that the parasites do
indeed make them eat more PAs

00:03:04.000 --> 00:03:05.990 align:middle line:84%
and tolerate strange,
bitter chemicals.

00:03:05.990 --> 00:03:08.080 align:middle line:84%
And this helps them get
rid of the parasites.

00:03:08.080 --> 00:03:10.750 align:middle line:84%
And so even caterpillars
can self-medicate.

00:03:10.750 --> 00:03:13.930 align:middle line:90%
[LAUGHTER]

00:03:13.930 --> 00:03:19.720 align:middle line:90%


00:03:19.720 --> 00:03:22.030 align:middle line:84%
I love all this
neurophysiology stuff.

00:03:22.030 --> 00:03:25.690 align:middle line:84%
Because actually, what's
amazing with insects

00:03:25.690 --> 00:03:31.030 align:middle line:84%
is what the taste cells
respond to is determining

00:03:31.030 --> 00:03:32.470 align:middle line:90%
a lot of the behavior.

00:03:32.470 --> 00:03:36.430 align:middle line:84%
And with ourselves and
a lot of vertebrates,

00:03:36.430 --> 00:03:40.600 align:middle line:84%
there's a more complicated issue
with the brain and experience,

00:03:40.600 --> 00:03:42.250 align:middle line:84%
not to say these
things don't learn.

00:03:42.250 --> 00:03:44.710 align:middle line:84%
But the fact that
their taste cells

00:03:44.710 --> 00:03:47.245 align:middle line:84%
can change with what
they need is just

00:03:47.245 --> 00:03:49.500 align:middle line:90%
something kind of different.

00:03:49.500 --> 00:03:53.770 align:middle line:84%
Are their taste cells
responding to some chemical

00:03:53.770 --> 00:03:57.640 align:middle line:90%
released by the parasite?

00:03:57.640 --> 00:04:00.040 align:middle line:84%
We don't know the precise
feedback mechanism

00:04:00.040 --> 00:04:00.690 align:middle line:90%
at this point.

00:04:00.690 --> 00:04:03.950 align:middle line:84%
That's one of the
issues we need to know.

00:04:03.950 --> 00:04:07.420 align:middle line:84%
And so, anyway, I
love all these spikes.

00:04:07.420 --> 00:04:09.940 align:middle line:84%
And these are
called spike trains.

00:04:09.940 --> 00:04:13.495 align:middle line:84%
And these are a
load of spike trains

00:04:13.495 --> 00:04:16.269 align:middle line:90%
over half-a-second interval.

00:04:16.269 --> 00:04:17.950 align:middle line:90%
It looks like the broadside.

00:04:17.950 --> 00:04:19.690 align:middle line:90%
Yeah.

00:04:19.690 --> 00:04:21.250 align:middle line:90%
This is right.

00:04:21.250 --> 00:04:22.120 align:middle line:90%
So here we are.

00:04:22.120 --> 00:04:23.560 align:middle line:90%
"Precision."

00:04:23.560 --> 00:04:28.630 align:middle line:84%
"Spike trains thread through
a Siberia of nerve cells.

00:04:28.630 --> 00:04:31.060 align:middle line:90%
Messages synapse.

00:04:31.060 --> 00:04:34.570 align:middle line:84%
Whispers of sodium
and potassium engage

00:04:34.570 --> 00:04:36.880 align:middle line:90%
in organization memories.

00:04:36.880 --> 00:04:39.730 align:middle line:90%
Voices vie for attention.

00:04:39.730 --> 00:04:44.230 align:middle line:84%
Serotonin, tryptamine,
octopamine open doors

00:04:44.230 --> 00:04:48.940 align:middle line:84%
or close them, change
receiver cells,

00:04:48.940 --> 00:04:52.360 align:middle line:84%
vary values of
electric language.

00:04:52.360 --> 00:04:57.400 align:middle line:84%
The spike trains of nerves,
interplay of inconstancies,

00:04:57.400 --> 00:04:59.860 align:middle line:90%
yet without indecision.

00:04:59.860 --> 00:05:02.840 align:middle line:90%
Stranger than fiction."

00:05:02.840 --> 00:05:04.720 align:middle line:84%
And I have some
woolly bears for you.

00:05:04.720 --> 00:05:08.290 align:middle line:90%


00:05:08.290 --> 00:05:09.250 align:middle line:90%
This is Grammia.

00:05:09.250 --> 00:05:11.080 align:middle line:84%
It's not the one that
I've been talking--

00:05:11.080 --> 00:05:11.890 align:middle line:90%
it's not this.

00:05:11.890 --> 00:05:13.930 align:middle line:90%
But it's a related one.

00:05:13.930 --> 00:05:20.320 align:middle line:84%
And in that box of insects, you
had some specimens of Grammia.

00:05:20.320 --> 00:05:22.060 align:middle line:84%
And these are
caterpillars of Grammia

00:05:22.060 --> 00:05:24.610 align:middle line:84%
that I collected
a week or so back

00:05:24.610 --> 00:05:26.920 align:middle line:90%
in the Patagonia mountains.

00:05:26.920 --> 00:05:29.980 align:middle line:84%
Again, they're feeding
on synthetic diet.

00:05:29.980 --> 00:05:31.630 align:middle line:90%
You're welcome to pick them up.

00:05:31.630 --> 00:05:32.510 align:middle line:90%
They're really cute.

00:05:32.510 --> 00:05:36.640 align:middle line:90%
They're not bad for you at all.

00:05:36.640 --> 00:05:39.280 align:middle line:84%
They're surprisingly good
at escaping, however.

00:05:39.280 --> 00:05:43.420 align:middle line:84%
So if you pick them up, I
suggest you do it over the dish

00:05:43.420 --> 00:05:48.830 align:middle line:84%
so that when they get out of
your control, they go back in.

00:05:48.830 --> 00:05:53.360 align:middle line:84%
So that's really the end of
what I want to tell you about.

00:05:53.360 --> 00:05:57.380 align:middle line:84%
And I'll leave you
to play with Grammia.

00:05:57.380 --> 00:06:00.730 align:middle line:90%
[APPLAUSE]

00:06:00.730 --> 00:06:02.000 align:middle line:90%