Thank you very much.
I have a long list of
Melanie's accomplishments
here, which I'm going to
ignore because I've known
Melanie for many, many years.
And it's a great pleasure to
introduce her to you tonight.
Melanie received her PhD from
the University of London,
working in the British
Museum of Natural History.
We overlapped a little
bit at that time,
when I was doing some
research there myself.
And after that, Melanie
came to Harvard,
where she worked as curator
of fishes and professor
of organismic and
evolutionary biology
here for almost five years
before moving to the American
Museum of Natural History,
where she's now Axelrod Curator.
She's involved in
the graduate program
there, with Columbia University.
She's become widely
known for her work
on the evolution of fishes.
And she's, I think,
believe, chair
of the fish department
there at the American
Museum of Natural History.
Melanie's research
has just spanned
so many different
aspects of fish biology.
And including studies of their
structure and their evolution,
focusing for some
time on cichlid
fishes, a very well-known group
of an evolutionary test case.
But more recently, she's
expanded her work out
into major field
efforts, such as you're
going to hear about tonight,
the remarkable situation she's
uncovered in the Congo River.
And it's actually, when I teach
biology of fishes, usually
every other year, in the
spring here at Harvard,
I use her material
from this case study
to introduce the
undergraduate students
to an amazing evolutionary
microcosm, that really
integrates geology,
ecology, behavior,
and evolutionary
diversification of fishes.
It's an amazing
system, that she really
has been the sole person
responsible for developing
and pulling a huge team
together to address this.
So with great
pleasure, I'm going
to now introduce Melanie
Stiassny of the American
Museum of Natural History in
New York, who will tell you
about evolution
and diversification
in Congo River fishes.
[APPLAUSE]
Thank you.
Thank you so much George for
that lovely introduction.
It really is a
pleasure to be here
and to have a chance to
talk with you a little bit
about, as George
said, some of the work
that I've been doing recently.
Well, I say recently.
But I kind of-- my first
slide-- sorry, my first slide
is going to show
you this cartoon.
I say, recently.
It feels like I've
been in the Congo
since 1884, like
these gentlemen.
But, in fact, my work there
really began in about 2006.
So I've been going there
for a long time now.
And I'm going to
kind of start off
by-- I know that we're going
to be talking about collections
and the importance
of collections.
But I'm going to
start off by talking
about my study area,
some of the things
that I've been finding there.
And then I'll segue into
the collection side of it
and what we actually do with
all of these collections
that I've been making.
So to start off, I'm
going to talk a little bit
about the Congo Basin.
So Africa, I'm sure you're
all very familiar with.
And the Congo Basin,
I can slot in there.
Now, the Congo is really the
freshwater heart of Africa.
It's a place of superlatives.
It's the world's second
largest river basin.
It drains some 4 million
square kilometers
of land in Central Africa.
That's about the size
of Western Europe.
It's a massive drainage basin.
The source waters
take about six months,
from their source
in the southeast,
to make it to the
Atlantic Ocean.
And the Congo River also
provides about 14 and 1/2
thousand kilometers of navigable
passage across Central Africa.
And it provides the food
and livelihoods for about 60
million people who live there.
And it's become
increasingly important.
Because I know a
lot of you, you read
about the war in the Congo.
And most of the drainage
of the Congo Basin
is actually situated
in the country
of the Democratic
Republic of Congo.
Congo is going through,
and is still going through,
some really tough times.
And amazingly,
today, in a country
the size of Western
Europe, there
are about 300 kilometers
of paved road.
So the river is an incredibly
important component
for the peoples of this
region, just to get around,
and to conduct trade,
and do everything.
And my next slide, I don't
know if you can see this.
It looks like a
floating island, right?
This is actually a barge.
So here you can see
the motor of it.
And it's moving slowly
up the Congo River,
carrying all these people
and all their goods.
So it's a really amazing
picture, I think,
that kind of gives us a sense
of the importance of the Congo.
But I'm going to be talking
of its biological importance.
And to kind of situate what
I'm going to be talking about,
I've kind of colored in the
main stem of the Congo River.
So arising here, looping round,
through the heart of Africa.
And actually, it's
cut off in this slide.
But it's actually flowing
out into the Atlantic Ocean.
Now, I want to draw your
attention first just
to this little round thing here.
And what that is is actually
a very strange expansion
in the middle of
the Congo River.
It used to be
called Stanley Pool.
And nowadays, it's
called Pool Malebo.
And the area of
the Congo that I'm
going to be talking
about-- sorry,
probably I should just
go back-- is really
from that expansion,
which I'm going
to be talking a
little more about,
down to the Atlantic River.
That small stretch,
a tiny percentage
of the Congo Basin
itself, is what
I'm going to be talking about.
And in my next slide, I've
just kind of highlighted that.
So here's this strange swelling.
Above it, the middle
Congo River flows.
Then you come down to
this strange swelling.
And then the river
spills out over a spill
and plunges down, this
lower Congo River,
to its outflow in
the Atlantic Ocean.
So that's just a short stretch.
And I'm going to be
talking a lot about it.
It's just about 300
kilometers in length.
But just quickly,
to look up here,
you can see this strange, very
strange, kind of a expansion
in the middle of the Congo
River, which is, as I
say what's called Stanley Pool.
And we now know
it as Pool Malebo.
It's a very strange structure.
We know very little
about the geology,
the geological history of it.
But as far as fishes
are concerned,
it forms a biological barrier.
The kind of things that you
see above the pool, fish-wise,
and the things that
you see below the pool,
fish-wise, are very different.
And if I just show
you this picture,
this is actually a
picture taken in the pool.
And the pool itself
is very shallow.
It's very sandy.
It's very different
from the kind of river
that's above the pool,
the middle Congo River.
And I think that's much more
like the kind of African Queen,
that you think about, the big
meandering river, the leeches,
the flies, the heat.
Above the pool, it gets
very African Queenish.
The pool, very shallow,
spills out, sandy.
And then below the pool, in this
study region of mine, the lower
Congo River, it's
hugely tumultuous,
turbulent, high energy.
And you going to see
quite a lot about that.
So this strange swelling really
forms a biogeographical barrier
for the fishes above and below.
It seems to separate
them pretty well.
OK.
So this is basically
what we knew when
my work began, back in 2006.
And this is taken from a paper.
And I'm sure you'll recognize
the journal, from the Bulletin
here of the MCZ.
And two ichthyologists, Tyson
Roberts and Don Stewart,
really undertook
the first study,
the first look at the fishes
of the lower Congo River.
And this paper was really
the first to document
that there's something
interesting about the lower
Congo River.
If we just look at
the numbers, you'll
see that Roberts and Stewart,
in their study, which
was published in '76,
they recorded 129 species
from the Lower Congo.
And remember, this is a
short stretch of river.
At the time, there were
only about 600 species
known from the entire Congo.
So 129 from the Lower Congo,
a tiny little stretch,
was interesting.
And so something's going on.
And think about it.
Actually in Europe, freshwater
fishes of Europe are about 200,
in all of Western Europe.
So 129 in 300
kilometers is a lot.
But more interesting
in a way was
that Roberts and Stewart found
that 34 of them were endemic.
34 of those species are only
known from the lower Congo
River.
So there's something
interesting.
And that paper was the first
to really point that out.
And that's basically
what we knew in 2006.
Now, I am one to boast.
But I don't mean to boast.
Since our work began,
we've done nothing
but add to those numbers.
Now, the lower Congo River, we
found over 330 species there.
And we found over 85
of them are endemic.
So clearly something
very, very interesting
is going on in this
stretch of river.
If we look very quickly, and I
know it's a rather small slide,
but if we look at
the endemic species.
So these are the species that
presumably have evolved in situ
in the lower Congo River.
If we look at them--
and they're, as I say,
there were over
85 and counting--
you can see very quickly
that whatever's happening
seems to be happening
and affecting
all of the families of fishes,
all of the types of fishes
that occur in the Lower Congo.
They all are spinning
off endemic species.
So whether you're a
catfish, or a spiny eel,
or a lungfish,
whatever you are, it
seems that whatever's happening
in the lower Congo River,
it's affecting you.
Now, some groups
more than others.
And George mentioned cichlids.
And cichlids are these iconic
fishes of evolutionary biology.
And everyone's familiar with
the extraordinary radiations
of cichlids fishes in the
Great Lakes of East and Central
Africa.
In the river, cichlids
don't tend to speciate.
That's a kind of orthodoxy
that we've all grown up with.
They speciate in lakes,
but not in rivers.
The lower Congo River
is a real exception.
And there are about 35
species of cichlids found
in that tiny stretch of river.
And 25 of them are endemic
to that stretch of river.
So something is going on.
Now, you could say, and if
we look at this next map.
And what I've done
here is divided Africa
up into what are
generally considered
to be ichthyofaunal regions.
So there's Lower
Guinea, Congo, Cuanza.
These are areas of
Africa where you would
find a certain kind of fishes.
That geographical
area, even if I
didn't know where
you'd been fishing,
but if you showed me
some fish, I could say,
oh, you probably made those
collections in the Cuanza.
We can divide Africa
up, the fishes
of Africa up in this way.
And look where Lower Congo is.
We all know realtors tell us,
location, location, location.
If you're nestled between
three big ichthyofaunal areas,
you could readily imagine
that the reason that the Lower
Congo has got so
many species in it
doesn't explain
in-situ speciation.
But why it's got so
many fish species
there might be because it's
getting some from Lower Guinea.
It's getting some from Cuanza.
And it's getting
some from Congo.
So it's just its
location that accounts
for that incredible richness.
But that clearly isn't the case.
And I know everyone
kind of hazes
over when they see one of
these phylogenetic trees.
But we can use this.
And this was just for cichlids.
But it holds true for just
about all of the fish groups
that we've studied.
Is when you actually
look phylogenetically
at those endemic species
from the Lower Congo,
and you find out who are
they most closely related to,
virtually every time
their sister species
is either found
in the Lower Congo
or it's found in the
Congo Basin generally.
It's very rarely
from anywhere else.
So it really looks as if this
area, the lower Congo River,
has been almost entirely seeded,
the diversification there
has been seeded from
the Congo itself.
So what is it?
What is it about this short
stretch of the Congo River
that has turned it into
this evolutionary hotspot
of freshwater fish biodiversity?
And we can look
a little bit more
closely at that Lower
Congo, so from the pool
down to the Atlantic Ocean.
And what we have above here is
an elevational cross-section.
And what you see immediately
is that the pool, Pool Malebo,
is at about 280 meters
above sea level.
The lower Congo River drops
in elevation, about 280 meters
in elevation, in a little
more than 300 kilometers,
an incredible, rapid
gradational decline.
And it does it stepwise and
in a very interesting way.
And the result, remember I said
the Congo is draining-- well,
I hope I said it-- 4 million
square kilometers of Central
Africa.
It's draining that.
All of that water is coming down
and it's hitting Pool Malebo.
And then it's
falling over a sill.
And then it's plunging
down, literally
plunging down, from Pool
Malebo, down to the Atlantic.
And how much water is it?
Well, it's about 41,000 cubic
meters of water a second.
That is three times the flow
of the Mississippi River.
The Mississippi River flows
over a great flood plain.
Yes, we've constrained
it and engineered it.
But it's a big river,
with a big flood plain.
All of that water, three times
the flow of the Mississippi,
is plunging down a
gorge constrained
in places less than half
a kilometer across gorge.
And the upshot is a lot of this.
And I'm just going to quickly
show you this video, which
is not a very good video.
[CRASHING RAPIDS]
But I'm going to let it
run for a little bit.
So what we have here--
sorry-- is the first rapid
when the river flows
out of Pool Malebo.
And I just want to
point out the scale.
That is a 6 foot guy there.
And these rapids span
the width of the Congo.
It's incredible.
Some of these rapids
are beyond belief.
Now, clearly a system
like this, there's
tremendous potential for these
series of rapids of this kind
dimension, that they clearly
could have played an incredibly
important role in the
diversification of populations
and of species in this system.
I mean you can imagine some
species are adapted to a rapid.
So they're going to
hang out in the rapid.
And then the still water between
that rapid and the next rapid
is going to be a barrier.
Or if they're adapted
to still water,
the next rapid is
going to be a barrier.
So you can see
how longitudinally
these extreme
hydrological structures,
rapid, so-called calm stretch,
rapid, calm stretch, how
that could really kind of
help pump speciation out
through simple
allopatric speciation.
And I'm going to talk about
some of that in a minute.
But before I do, I want
to mention very briefly
one of the first problems
that we had to deal with.
Basically, we knew there
were a lot of rapids
in the lower Congo River.
But the problem was
we didn't really
know where the rapids were.
We had maps.
And there were some
very good maps.
And many Belgians
lost their lives,
spending all of their careers
trying to map the Congo Basin.
And the maps are good.
We have topographical maps.
And we now have Landsat imagery.
And they're very good.
And they're very accurate.
And they tell us a lot about
land form and land cover.
But they don't really tell
us anything about what's
happening in the water itself.
This map doesn't tell
me where the rapids are.
So one of the very
first things we
had to do was to
work out, well, how
are we going to find out
where all the rapids are?
And, until recently, to
do that we would have
had to work directly
via field work.
But that's virtually impossible.
Because I told
you that the Lower
Congo plunges through a gorge.
So most of the habitation, most
of the paths, most of the ways
you get around in
the Lower Congo
is a long way from
the river itself.
So access to the river
is extremely difficult.
And as you can
imagine from seeing
that video of the
rapids, you can't really
do it from the water.
There's no way
you could do that.
So it's really problematical.
So you're in this gorge.
And even if you
can get down there,
it's extremely difficult
to collect in this system.
So clearly we couldn't do
our mapping by field work.
So what we actually
did was we utilized
a way of looking at the
nuances of radiation
from some of these
remotely sensed data
sets that we got, using
object-oriented analysis.
And we could really build up
a picture a little bit more
of what was going
on in the water.
And I just want to show
you very quickly this.
And I will whiz through it a
bit because its rather long.
So many of you are very
familiar with these kind of ways
of looking at land cover.
But you can actually
do it looking
at the actual form of the
height of the water itself.
So what you can see
here in these blue areas
are where we're mapping
the calm stretches.
And then you can see,
in the light blue,
we're actually able to map where
some of these rapid systems
are.
And here's a good
example of one.
So this whole system here
would count as one rapid
that we would be able to map.
So that was the first
thing we had to do.
And we basically got
a pretty good idea
of where all the
rapids actually were,
these big hydrological
structures that
crossed the channel.
And there they are.
And perhaps, not surprisingly,
when we mapped out
some of our species
distributions,
it was very, very
clear that, yes,
these rapids are forming
barriers to some species.
And speciation has clearly been
through allopatric separation
of species.
You're in a rapid or
you're not in a rapid.
You're not going to
move across still water
to get to another rapid.
So very clear.
It's a good story.
And it makes sense.
Rapids do present barriers to
fishes, of varying efficacy.
And we do see longitudinal
structuring of species
down the lower Congo River.
But we were also,
at the same time,
beginning to document
extremely, surprisingly,
low levels of migration,
of populations, individuals
from populations within
a species, up, down,
up and down the Congo
River, of the Lower Congo.
And in this example, and I
know it's a complicated slide,
and I'm not going to
dwell on the details.
But in this case, we looked
at various molecular markers.
So we got individuals
in the first case
of this cichlid,
Teleogramma depressum.
And it only occurs in site
A, site B, and site C.
And we got populations from
each of those locations.
And we took DNA
from their tissues.
And we looked at various
mitochondrial markers
and we looked at some
anonymous nuclear markers.
And we saw a lot of structure.
And you can see that,
quite clearly in this case,
the populations at
site A are quite
distinct from the populations
at site B. So in this case,
there's the break.
And it looks very much
as if these rapids here
are probably separating
the individuals
of the species from here.
And there's very little
communication with the species
just a little way
down the river.
We found a similar
story with this guy.
This is another cichlid,
Lamprologus tigripictilis.
It's a little more complicated.
This is a much more widespread
animal, but a similar story.
But this time,
interestingly, the barrier
seems to be at a
different place.
It's after the last
large major rapids.
You're separating
populations, from and D and E,
from the rest of them.
So really fine scale kind of
stuff that you don't really
expect at this sort of level.
So that was interesting.
But then, we also
began to pick up
cross-channel diversification.
So in this case, we're back with
our profile of the lower Congo
River.
Here's Pool Malebo.
There are the first rapids
after Pool Malebo, which is what
I just showed you the video of.
At this point here,
here it is, we made
collections of this species.
We made collections on
either side of the rapids,
on either side of the river.
And we're talking about
a distance of less than 1
and 1/2 kilometers.
When we did the same kind
of analysis with these,
we found that the
population structuring here,
at an even finer geographical
scale, was even clearer.
And in this case,
we found that there
was at least 5% sequence
divergence between populations
living here and
populations living there,
looking to all
intents and purposes
pretty much like the same thing.
But obviously,
they are separated.
They're not crossing
the-- well, we
can work out exactly how
often they're crossing.
And it's very, very few, in a
large number of generations,
makes it across the Congo River.
So extreme example.
I mean this is like-- when I
give this talk in New York,
it's like saying
people in Manhattan
are not going to be breeding
with people in Hoboken.
And I guess here you would
say that people in Boston
are not having anything to
do with people in Cambridge
because the Charles River,
they've got to get across it.
I mean it's at
that kind of scale.
It was very surprising.
So clearly something
interesting is going on.
These very low
levels of gene flow
between populations that
are geographically so close
to each other, very likely
what we're looking at
is the early processes
of ecological speciation.
You can imagine that
these populations,
either side of the
rapids, they're
adapting to local conditions.
And over time, it's the
classic evolutionary story.
Over time, they're
going to diverge.
So it's kind of cool.
But remember, these
are fish, not people.
So we want to think
about, well, how
are the fish seeing the river?
I mean we look at
it and we think, ah,
it's a piece of water.
They can go across
it, no problem.
But clearly the fish don't
view the water in that way.
So one thing that
we really wanted
to do to add to this picture was
to understand what was actually
going on in the
water and look at it
from a fish's perspective.
Now, the very best
way to do this
is to utilize the pleiotropic
effect of the Y chromosome.
[LAUGHTER]
Because one of those
is that they are crazy.
And we managed to persuade
a bunch of these--
they were fabulous guys-- a
bunch of wonderful white water
kayakers.
And the hardest thing-- well,
it was not hard to say to them,
go into that rapid.
That was easy.
It was hard to stop them
going into the rapid.
The hardest thing
was to actually allow
us to drill a hole in
the bottom of their kayak
so we could put a sound--
sorry, an echosounder so
that we could measure depth.
But they let us do it.
So we put the echosounders
in so we're measuring depth.
And then we have
this differential GPS
so we can locate exactly
where they are in the river.
And this is some of the
stuff that they encountered.
And I'll only do a bit of it.
[AUDIO PLAYBACK]
-And Scott crashed
head-first into waves
the size of school buses,
each weighing about 30 tons.
-Yeah, crazy.
All right.
[END PLAYBACK]
OK.
OK.
So we were beginning to
document strong structuring
of populations, clearly
mediated in some way
by these extreme hydrological
features in this river,
particularly I'm talking
about the rapids.
And we were finding
up and down the river,
structuring of populations.
And we were finding
cross-channel,
where there were rapids,
differentiation in species.
So lots of structuring.
But at the same time,
we were beginning
to get clues that something
else was at play in the system.
In places, we were
beginning to pick up
this signal of cross-channel
diversification
in fish populations in
the absence of rapids.
And that was really puzzling.
Now at one site in
particular, and it's
this place called Bulu.
And it is marked here.
So here's the pool.
So Bulu is where the
river, after expanding
in this stretch, which, if
you remember-- I'm sorry.
I should have
pointed it out when
I showed you with the
locations of the rapids.
There's a clustering
of rapids down
in this area and another
clustering of rapids here.
But there's a stretch
that certainly
doesn't look like there
were any surface rapids.
Anyway, so Bulu is just the
end of that place that seems
to not have any surface rapids.
And it's at a place where you
get the first constriction
of the channel.
And the channel constricts
down from about 1
and 1/2 kilometers across,
down to about half a kilometer
across.
So there's a real
constriction there.
And at Bulu, a very strange
fish had been found.
And Roberts and
Stewart had found it.
Back in '76, they visited Bulu.
And they found
this cichlid fish,
which I know you're
not all cichlid lovers.
Nobody's perfect.
But this is a very
unusual cichlid.
It's completely blind.
And it's completely depigmented.
Now, Roberts and Stewart
managed to collect
two specimens of this fish.
And they tried and they
tried and they tried.
They even-- after the
expedition was over,
they went back to Bulu to see
if they could collect more.
And they couldn't.
So this fish, which
its scientific name
is Lamprologus
lethops, was known only
from those two specimens.
So we figured, well,
it was important.
We need to get Bulu.
We need to get
more of this fish.
Because to have a blind
depigmented cichlid
is very cool.
It could tell us a
lot about evolution.
So we went back and we
searched and we searched.
Our initial thought was
the animal is blind.
It's got no eyes.
It's a cave fish.
We know that in cave
habitats, you quite often
get this series of losses of
pigmentation, losses of vision,
and all the rest of it.
We scoured the place,
no caves, no caves.
We looked and we looked.
We asked the local
people-- and I
think I just have a
little video, which
I'm going to skip because it's
just of us pulling into Bulu.
We asked the local people
if they knew the fish?
And they said, sure, we know it.
It tastes disgusting.
[LAUGHTER]
They call it mondele
bureau, which is very, very
strange because "mondele"
is the Congolese word
for white person.
And "bureau" is obviously
French for office.
So for some reason, they called
it the white man's office.
And the only thing
that I can think of
is that I could just imagine
Tyson and Roberts coming
to Bulu with a suit case.
Can't you?
Can you, with his briefcase,
from marching down
the shore of the river.
I don't know.
But anyway, they said
yes, we know the fish.
We call it mondele bureau.
It tastes disgusting.
And we only find it dead.
So we were like what?
They said yeah, yeah.
Occasionally, we'll find one
on the side of the river.
Oh, we were like OK, but really?
Anyway, we stayed at that place.
We looked and we looked.
Unfortunately, many
fish lost their lives
as we searched for some
of these blind cichlids.
But we couldn't find any.
But after a while
of being there,
some local fishermen
came up with-- am I
in the right place--
a couple of specimens.
And they were dead,
just as they said.
They'd found them by the
side of the river, dead.
And there are two of
them that I'm holding.
Now, while we stayed and
tried to unravel mystery,
they came to me with one of
these mondele bureau, one
of these Lamprologus lethops,
that was not quite dead.
The poor little thing, it
actually died in my hand.
But it was moribund.
It was close to death.
But it was alive.
And as it died, we noticed
something very interesting.
And that was that its entire
body was full of bubbles.
I don't if you can see that.
I kind of outlined it just
because you can't really
see because the fish is
so kind of translucent.
But there were bubbles.
There were air bubbles
under its skin.
There were air bubbles along
its cheeks, under its skin.
There were air bubbles
all over its gills.
And that was the first time.
It just occurred to us.
This guy looks like
it's got the bends.
It looks like it's decompressed.
It looks like it's got
what's called catastrophic--
it was clearly, or it was
very likely, living at depth
and had somehow come up to the
surface and had decompressed.
Catastrophic decompression
syndrome, which we do
know about because that
can be induced in fishes
under various conditions.
One of them would
be you pull him
up from deep sea with a
fishing line very quickly.
They will get the bends.
They will degas.
And they will die.
So for the first time,
because of this fish,
we suddenly thought, well,
maybe there's deep water here.
And that's something nobody
had-- it never occurred to us.
We just thought about rapids.
So based on that, we were
able to persuade some guys
from the US Geological Survey
and National Geographic
to fund us deploying
some quite sophisticated
hydrological equipment.
And we really did deploy
for the first time
in a tropical system, acoustic
Doppler current profilers.
And I'm going to show you
a little video of these,
just to give you a sense
of what these things do.
And one of the things that
these things do-- and again, we
can have a depth trace
and we've got GPS.
But what this thing
is doing-- and you're
going to see it in a
minute-- not only can you
make a depth profile, so we can
actually see how deep it is,
but we can also
map the structure
in the water, the
velocity of the water.
Now, this is done in
marine systems quite a lot.
It's not been done very
much in freshwater systems.
But because of the
backscatter of all
of the sediment in the water,
we can actually visualize this.
So that's what we did.
And the place I'm going
to talk was at Bulu.
So in Bulu, this is where
the blind cichlid was.
This is where we thought
maybe there's deep water here.
So just to quickly orient you,
so here we have the curve.
And on the black line, showing
you where we deployed the ADCP.
And you can see along
the bottom here,
we've just got a
bathymetry profile.
And first of all,
I'm going to show
you the ADCP at this point.
Now, this is the first
bend in the river at Bulu.
There were absolutely
no surface rapids.
The water looked
completely normal.
But when we actually-- and I'm
going to show you a-- oops,
I'm going to show you a trace.
And here's the trace.
Just to orient you
what's going on,
you are standing in the
middle of the of the riverbed
and you're looking downstream.
So this is a cross-section.
And what the color
is coding-- the color
is giving you the
streamwise velocity.
And red water is flowing
extremely fast downstream.
But the blue water is
flowing fast upstream.
So we've got rivers
within rivers.
And we have a complete shear.
I mean there are no
water structures that
span that channel.
You have a complete shear here.
So this bank is completely
separated from that bank.
If a little fish could swim
out and it would hit the red,
it would plunge it downstream.
So for the first time,
we were beginning
to actually see why
there was such structure
for these fishes.
I mean you've got a
river within a river.
Remember, this is less than
half a kilometer across.
Yet, they might as well
be a hundred miles apart.
Because for a fish to
swim through this--
a small little fish that
likes to live on the banks
and around the rocks is not
going to make it across.
So it's quite clear
that the river itself
seems to be what's the barrier
for these fishes, which
is totally wacko.
Because we always
think of water as being
the passage for the fishes.
But here, the water itself,
the hydrology of this system,
is actually separating
populations of fishes.
So that's kind of cool.
Now, the next place we
looked was at this point
here, which is innocently
labeled as a pool.
Now, we couldn't go over
the center of that region
because-- well, you're going
to see why in a minute.
But we were in 50-foot
wooden pirogues.
And we nearly lost
them in this attempt.
And this is what we
were looking at here.
First off, I hope you can see
it, but look at the depth.
This, now, we're talking
about, at its deepest
point, 165 meters, so about 540
feet deep, tremendous depth.
But now the colors
of the water are not
telling you how the water's
going upstream and downstream.
They're telling you how
it's going up and down.
So you have these
tremendous water seas.
This water is plunging upwards.
This water is plunging down.
And just to give you a little
sense of the scale of it,
these are kayaks.
And this is one of
these water seas.
If this gets into
this, it's going
to get pulled down for 500 feet,
to the bottom of that hole.
I mean it's incredible.
These things we'd
seen, but we didn't
recognize what they were.
We haven't seen them
from this perspective.
When you are coming down
this stretch of river,
it looks like there's a hill
in the middle of the river.
And what that hill is is
the lip of this vortex.
And they're standing structures.
I mean it's really
absolutely extraordinary.
And you can so imagine
if a small fish, living
at extreme depth, gets
entrained in one of these water
seas-- you know, you're
living on the bottom.
You're kind of adapted to it.
And then you see
something to eat
and you maybe swim up
a little bit too much.
And then you get
entrained in one of these.
You come up to the surface.
You catastrophically decompress.
And you're dead.
So it looks as if
that's what's happening.
That's a kind of little
solving of the mystery.
But the serendipity
of collections,
how making collections, kind
of then led on to-- this
is the deepest
river in the world.
It has canyons in it that
are way below sea level.
So remember the crazy
kayakers, right?
There he is,
heading down for us.
So let's look at what they got.
Now, remember these guys
did not have the ADCP.
They weren't measuring
the velocity of water
and looking at the complexity
of the water column.
They were just
looking at the depth.
Basically, they were
just looking at the depth
as they went downstream.
And they went down a section
of about 120 kilometers,
from the pool, down
to the beginning
of that navigable stretch.
So they did the
first set of rapids.
And here is the trace.
And I want you see
this, 800 feet.
This is not meters.
We're not in the ocean.
800 feet, the hole, the
canyon that we found at Bulu,
it looks like a
paddling pool compared
to some of these things.
So clearly an
extraordinary system.
And I will get back to a
kind of conclusion with it.
But I want to probably
wind up very quickly.
So I want to very
briefly-- and I really
will do this very briefly--
to talk just a little bit
about how we could--
you know, I've
collected thousands of fish.
And I got this very weird fish.
I want to talk very, very
quickly about some of the ways
that we can use these specimens
that we have in museum
collections to actually
start to begin to unravel
some of the
evolutionary questions
that a system like this poses.
Obviously, just
having collections
in and of themselves,
alcoholic-preserved specimens,
is tremendously important.
We need to know where
life on the planet
is, when it was where it was.
We can look at it through time
because of these collections.
Just having the specimens
is tremendously important.
But there's a whole series
of ways that we can view--
and I'm going to be
talking about fish.
But this is probably
true for most organisms.
There are many ways we can
deal with fish specimens.
We can make skeletal
preparations.
Obviously, looking
at bones can tell us
some important big things
about fish anatomy.
And we've been doing
this for centuries.
We can do it in a
much more refined way.
We can use enzymes to clear
away the body tissues.
And then we can differentially
stain with alizarin red
to stain bones and calcium
blue to stain cartilage.
We can get very detailed
anatomical specimens,
which can be dissected.
So here, taking off the
jaws, and the suspensorium,
and the pharynx.
So we can do that.
Of course, today we
can also extract DNA
from these specimens.
And we can extract
the DNA and then
we can amplify certain genes.
And we can then use
this data, looking
at the differences
in sequence structure
of different genes in numerous
different individuals.
And we can use that for
the very basic baseline
information of
comparative biology
and evolutionary biology.
The first question,
who's related to who?
So to produce phylogenetic
trees, we can do that.
And I'm not going to go
into the details of it.
But here are our lethops.
And it turns out that
the sister to lethops
is Lamprologus tigripictilis.
So we now know
who the sister is.
That's very, very
important information.
That's the baseline.
And we can do that with DNA.
It's easier to do it with
DNA than with anatomy.
But once we have
that relationship,
then we can use these anatomical
features, in this case,
this clearing and staining.
And we can look in
a little more detail
at the kind of gross differences
between these two species,
which are each other's
sister species.
They're each other's sister.
But they look so
different from each other.
And we can kind of look
at that qualitatively.
And we can see how the
skull is extremely expanded.
We could look at differences
in swim bladders.
We can also look at histology.
We can make thin sections
through these specimens.
And we can stain them
in ways that we can
look at the cellular structure.
And I know I'm
running out of time.
So I'm not going to dwell on it.
But here's the third thing.
Lamprologus lethops--
oops-- actually has eyes.
And here they are.
So this is the lethops
and there is its sister.
Its sister has
perfectly normal eyes.
Lethops has these
tiny regressed eyes,
which are situated under bone.
We can look at very
fine structure.
Histology is a wonderful thing.
We can look at the structure
of that reduced lethops eye.
We can even stain it using
immunohistochemistry.
We can actually see
whether there are
visual pigments in that eye.
There's a tremendous
amount of information
you can get out of
a museum specimen.
We can do all of that and we can
make all sorts of inferences.
And one of the inferences
is that lethops actually
is cryptophthalmic.
It has an eye.
It's a very reduced eye.
That eye is probably not
capable of forming an image.
But it probably is capable
of detecting light and dark.
So here we've got our
first bit of information
about the biology of this
animal, which we can't really
study in the field
because it would be easier
to go to the Marianas
Trench than it would
be to go to the bottom of one
of these trenches in the Congo
River.
But we can get a
lot of information
from a museum specimen.
I mean years ago, CT
scans were something
that you had when you blew
out your hip or something.
Now, we can CT scan.
So X-ray computed
tomography, CT scanning, we
can do that with fishes.
And we can get a tremendous
amount of information.
If lethops isn't seeing and
tigripictilis is seeing, well,
what about the brain structure?
Is it compensating?
Is it enhancing other
sensory modalities?
We can actually use these CT
scans to reconstruct things
like the brain.
So again, new
technologies are enabling
us to do amazing things
with museum specimens.
And, of course, today,
in the age of genomics,
we can go even further.
And, in fact, we're
in the process.
Because it's a cichlid, we have
a beautifully well-annotated
genome, not done by
us, but by others.
So we've got
something to compare.
Now, we've got enough DNA from
one of these dead specimens.
And we know now who
its sister species is.
We know this one has no eyes.
It has a hypertrophied
craniofacial anatomy-- well,
it hasn't yet--
cryptophthalmic eyes.
Its lost pigment.
We know what its
sister species is.
We can get their genomes.
We have this comparative genome.
So we can construct where every
gene in their genomes are.
And we can really
start to begin to get
at the real genetic
underpinning of what's
happening in this river,
thousands of miles from here,
that we-- well, OK.
I'm going to-- enough hyperbole.
So collections
have become-- they
haven't become less important.
Collections are
not old fashioned.
Collections really are
the key to the future.
They're the most
important things
that we can pass down
to next generations.
We must, must support
our collections.
Because we would
never have known--
I would even never
have known, when
I started my work, the kinds
of things, the kinds of data,
that we could get out of a
preserved museum specimen.
We can never second guess it.
The value of these collections
going forward, we have no idea.
So we have to protect them.
And as a plug for my
institution, the American
Museum, one of the
things that we've done
is we've started a new series.
It's called Shelf Life.
It's a really cool series,
talking about collections.
And if you're interested, the
title of this one that I did
was "Six Ways to
Prepare a Coelacanth."
And all the comments were,
garlic sauce, lemon butter.
Yeah.
No.
It's all about the CT, the
histology, and all of that.
So there's the URL there.
You can get it on YouTube or you
can get it through the Museum.
But it's a good series.
And I'm not-- I should
stop plugging it.
OK.
So I really know that I've
gone over my time probably.
So I hope that I've given
you a little idea of what
a fabulous system
the Lower Congo is.
I haven't got time to
go into all of this.
But I made a big deal
about Lamprologus
lethops and it sister species,
Lamprologus tigripictilis.
And they're here.
But there were numerous
other sister species, pairs,
in different families,
over the tree
of fish life, that are doing
exactly the same thing.
These are trends that reoccur
numerous times in the Lower
Congo.
It's such an extreme environment
that selective pressure
is huge.
And fishes from
completely unrelated,
as unrelated as
cows and gerbils,
are doing the same--
you know, it's
like you've got cows and gerbils
looking exactly the same.
That would be the equivalent
in phylogenetic time
of the difference between
these trees-- these fishes.
So it's a fabulous system.
And I'm going to
really have to show--
and I'm going to say you're
probably as exhausted
as I am when I leave
the Congo every year.
But I'll skip that.
And I'm going to skip
through all of this
because I just do not have time.
Obama, we love him.
OK.
And say, thank
you to all of you.
But I want to acknowledge
all of the people that
have helped me in
this work and continue
to help me on this work.
Those of which I am most
proud and most indebted
are my Congolese colleagues
and my Congolese students.
I can add, I'm happy to say,
I don't have her picture yet.
But I'm adding a young
woman, Myriam Yoko.
If she makes it
through, she will
be the first
Congolese woman PhD,
which will be really fabulous.
So thanks so much to them.
Thanks to all of the
other people, and funders,
and all the rest of it.
Clearly, it's not
just me doing this.
It's been a great
collaborative journey.
And, of course, to all of the
fish that gave their lives
and are now in the
collections at the Museum.
And I'll end with this.
I call this my
Mother Teresa shot.
But it's me in my favorite
place in the world
and my accommodations for
the next three and three
weeks in Congo.
So with that, I'm going to shut
up and entertain any questions.
I'm sorry I was so rushed.
[APPLAUSE]
