>>MELANIE STIASSNY: In 1962, the Museum gets a telegram from the Comorian archipelago…
“We have a coelacanth for you.”
The coelacanth is like an icon of evolutionary biology—a living representative of a very
ancient group of fishes that we thought had gone extinct maybe 65, 70 million years ago.
It would be like, you know, someone calls them up with a picture of a Tyrannosaurus,
saying, “This was running around the vegetable patch. You know, is it interesting?”
Yeah, it was.
My name’s Melanie Stiassny, and I’m one of the curators of fish here at the American
Museum of Natural History.
[TWINKLING MUSIC PLAYS]
>> STIASSNY: So, we had a visiting researcher here at the Museum and he’d requested to dissect the
coelacanth that we had. And to everyone’s surprise, when it was opened up, inside her
we found five embryonic coelacanths, five pups. It was her that basically taught us
that coelacanths give birth to live young.
They’re so super cute.
The thing about the coelacanth is they’re actually now very endangered. We can’t just
go out and get a coelacanth anymore. So, it was kind of a no-brainer that we were going
to try and prepare them in as many ways as possible, to get as much data out of them.
How we’re going to treat a specimen really depends on how many we’ve got, and what
the scientific questions are.
If we just have one specimen, a particularly rare specimen, we would still take a tissue
sample because that can be very non-invasive. We want to be able to have an archive of the
DNA of the organisms that we’re collecting.
And then the standard procedure would be to preserve, to fix it in formalin. The formalin
infuses all of the tissues and it just stops any process of decay. And then we transfer
them into ethanol.
And we know that this works because we have specimens that are hundreds of years old and
they’re absolutely fine.
But there are downsides to it.
The pigments that give the fishes their iridescence and their beautiful colors, which
are actually biologically really important, dissolve. They’re gone.
But a collection is not just a jar. I mean, it really is all of the contextual information.
And obviously, when we’re in the field, and we’re making a collection of fishes,
we try and take as many photographs as we can. Along with all of the notes about geographical
coordinates, about what we caught it with, what the water quality was like,
we have this record of what the fish looked like in life.
Skeletal specimens are really good for looking at big bits of anatomy. It’s a very nice
way of getting a three-dimensional representation, particularly a fish’s skull.
To make a skeletal specimen we actually use the larvae of beetles, dermestid beetles.
The little dermestid larvae nibble and nibble and nibble and it’s a fantastic process,
actually. You get this beautiful clean skeleton.
Cleared and stained specimens for fish are great because you just basically get this
see-through anatomy.
>>RADFORD ARRINDELL: We clear and stain mostly the smaller things
because that way we allow delicate elements
to remain intact without destroying them through dissection.
My name is Radford Arrindell, and I’m a senior scientific assistant in the Department
of Ichthyology.
The first step is to prepare the specimen by skinning and removing the eyes and the
gill arches.
The second step is actually the bleaching of the specimen to remove whatever pigment
remains within their tissues.
The third step would be to dehydrate the specimen in ethyl alcohol—like squeezing out a sponge—so
that their structures more readily pick up the dye.
The next step involves placing it in the blue stain. Blue is for the cartilage. Then it’s
placed in the enzyme solution to begin the clearing process.
After it’s partially cleared, where you can begin to see some of the structures, you
then begin the red stain The red stain goes to the bones, and once it’s been stained
all the way through you complete the clearing.
We then put it into glycerin where it will always keep the specimens moist and support
them. Because they are actually kind of floppy and fragile.
>> STIASSNY: With a serially sectioned specimen, basically, we’re making lots of slices.
And then each of those slices—
which are really, really thin—can then be stained differentially.
So, under a microscope, you can actually really see that very fine cellular detail. In many
ways, it’s the best thing you can have.
Now, with all of the new technologies we have, these collections become even more important,
even more rich.
I mean, when I first started, CT scanning–that was not something in our wildest
dreams that you thought you could afford to CT scan a fish. But now we can. So, we can
look in fabulous minute detail at anatomical structures. Amazing.
The critical and key thing is to have these specimens preserved and conserved for all time.
Here at the Museum, we have a collection of, you know, over two million fish specimens.
They go back 130 years. We could never reproduce what we’ve got here. Because the world has changed.
So, this is almost like a time capsule. Everything you read about, you know, the impacts of climate
change, how organisms’ distributions are changing, all of these things—it’s based
on specimens like these.