Why 11 Million Embalmed Specimens Are Stored In The Field Museum's Basement | Colossal Collections
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00:00From bonnethead sharks to big ol' Komodo dragons, more than 11 million fluid specimens live
00:09in the basement of the Field Museum in Chicago.
00:12There are 883 frogs in here.
00:15But why hold on to them all?
00:17And why keep them wet?
00:19Think of it like a library.
00:21Stored this way, wet specimens keep their shape and, in some cases, even DNA.
00:27Basically, the closest researchers can get to keeping a live zoo in their labs.
00:32Each jar is a book researchers can crack open and learn from, sometimes discovering brand
00:38new species right here on the shelves.
00:41But you can't just drop a Komodo dragon straight into a tank of alcohol.
00:45The Field Museum has to acquire and painstakingly prepare them so they can be preserved for
00:51centuries to come.
00:52The Field Museum acquires its specimens in two ways, either through donations, or sometimes
00:58researchers go out in the field to strategically euthanize specimens, like this common water
01:03snake.
01:04If you manage to grab one, they do not hesitate to bite.
01:08Sarah's research relies on new and old specimens to see how changes in habitat have affected
01:13the species over time.
01:15And the first thing she does with a new one is grab its DNA.
01:20This is a fairly new step in the process, since DNA wasn't really used the way it is
01:24now until the 90s.
01:26It's not impossible, but it is much easier to take tissue samples from fresh animals
01:33than it is to take them from preserved animals and get really good results.
01:37She uses scissors and forceps to collect the DNA sample, first sanitizing them by burning
01:42away any random DNA so the results aren't mixed.
01:46It does get so hot, though, that I have to dip it into some ethanol so that it doesn't
01:52essentially sear the animal as I work on it.
01:54Sarah takes the sample from the inside of the snake so she doesn't mess up what it looks
01:58like on the outside.
02:00The way I'm cutting is so that if somebody comes along, they're still going to be able
02:04to count these scales.
02:06Plus, that's right around where the liver is located.
02:09And there's the liver, right there.
02:11It's Sarah's favorite tissue to collect for DNA extraction because it dissolves easily.
02:15It turns everything pink.
02:17It says SR-1291.
02:20I double-check my tag is SR-1291.
02:23Then the DNA goes into these massive liquid nitrogen freezers with thousands of other
02:28DNA samples.
02:30Now she's ready for formalin, the liquid that preserves the tissue and keeps a specimen
02:34frozen in time.
02:36It's sort of like embalming it, just like a person at a funeral home.
02:40Sarah has to keep in mind what info she needs now and what researchers might need in the
02:45future, like the sex of the snake.
02:49It's always good to see if maybe if it's a male snake, if you can find the hemipenes
02:53and pop them out.
02:55Sarah will pose the snake so you can see the visible penises from outside the jar, without
03:00even opening it.
03:01In this pose is how it will stay for the rest of its afterlife.
03:05The coil doesn't just look snakey.
03:07There is some art to it.
03:09You can stack lots and lots of them on top of each other in a jar.
03:12One, two, three, four, I've got five snakes here and there's another probably six in this
03:20jar.
03:21Last step in this part of the process is tucking it in under a formalin soaked paper towel.
03:26It keeps the snake saturated without having to fill the tub.
03:30Good night snakey.
03:32Over a few days, the formalin will set into the tissue, leaving the snake fixed in place.
03:37Almost like you're holding a rubber snake.
03:40Larger animals might need more than a few injections, like this catfish Caleb is working on.
03:45Calculating the amount of formalin needed is mostly based on experience and feel.
03:50Too little and your specimen will start to decay and get floppy.
03:53Too much and your specimen will bloat and become disfigured.
03:57You don't want to make the belly do this because you've pumped it with so much formalin.
04:02Once Caleb is confident his catfish is sufficiently full, he'll move it into a tank of even more
04:07formalin to soak for about a week.
04:09We're going to add a bit of cheesecloth just to make sure that no parts of it are sitting
04:16outside of the formalin.
04:18After the formalin, the team switches over to alcohol baths for long-term preservation.
04:24Like with this Komodo dragon.
04:26The alcohol is less toxic than formalin, so it's safer for researchers in the long run.
04:31And the specimen doesn't change much while it sits in its final resting tank.
04:36Just the color of the liquid.
04:37Especially large specimens, they'll release a lot of debris and fatty oils that were stored
04:43in their body and it'll leach out into the ethanol and that causes a lot of the discoloration.
04:47But it's still doing its job in keeping the animal preserved.
04:51Most specimens in the WET collection are kept looking as lifelike as possible.
04:55But others...
04:56We can clear away all of the tissue, stain the bones and stain the cartilage, and we
05:01can end up with just a skeleton that we can put under a microscope.
05:05Extra small fish have extra small bones that are difficult to keep track of.
05:09So instead of isolating the skeleton, this method keeps it contained but visible inside
05:15the body.
05:16First step is dyeing the specimen blue.
05:19This specific blue dye is attracted to cartilage, and the red dye clings to calcium.
05:24A few days for each is typically enough to lock in the dye.
05:28The next step is to clear the fish.
05:30We use an enzyme called trypsin that digests proteins and breaks them down, but it leaves
05:36the collagen that holds everything together.
05:38Making the fish completely see-through.
05:40Finally, he dyes the bones red.
05:44One of the advantages of clearing the fish and then putting it into the red dye is you
05:48can keep an eye on it to see how dark it's getting.
05:50The whole process can run a few days to around a month.
05:54Done right, and your final product are these almost alien-looking specimens.
05:59It's kind of like jello.
06:01And you store it in glycerin in the end because glycerin and collagen have the same refractive
06:06index or the way that light passes through.
06:08These specimens go right into collections alongside all the opaque ones.
06:12So researchers can access them when all they want to see is bones and cartilage.
06:17You can put this under a microscope.
06:19You can move bones around and see how one bone moving affects other bones nearby.
06:24Entirely new species have been discovered this way.
06:27Like these two fish species that are identical on the outside.
06:31But when you clear and stain them and you look at their bones, you can actually see
06:35that there are differences in their skeletons between species.
06:38New species can hide on the shelves for decades.
06:42Like this spider-tailed horned viper, kept under lock and key.
06:46It was originally collected in the 1960s, and researchers first thought it was a different
06:52species of viper with an abnormality.
06:54This weird, weird parasite or a tumor.
06:58But then?
06:59In the early 2000s, some herpetologists came along and they said, you know, I think it's
07:05a whole new species altogether.
07:08Once a second one was found, they compared it to this one.
07:11And the species Pseudocerastes uroarachnoides was described from this very individual, this holotype.
07:18But specimens like this one are only helpful if you can find them.
07:22It's kind of like a library, but jars of fish.
07:25Different families of fishes have numbers, and then within each family, they're arranged
07:30alphabetically by genus and then by species.
07:33There's even a field in the database for noting when and where a specimen was last seen.
07:38So if someone asked for it, we know that, well, at least at this date, it was spotted
07:42on the shelf in the collection.
07:43And once you find it, it's not always as simple as pulling a jar off a shelf.
07:48There are 883 frogs in here.
07:51And each one has its own ID number.
07:53So if a researcher wants to look at a specific frog...
07:57I have to sit here and just pick each one up one by one, be like, no, not this one.
08:02No, not this one.
08:04Until you find the right one.
08:06These frogs used to be stored separately.
08:08But at times...
08:09We've definitely run out of space.
08:11They combined jars of the same species, but collected by different people, collected from
08:16different places, collected at different times.
08:19But then you end up with the same problem.
08:20I mentioned here.
08:22Getting rid of stuff is not an option.
08:24Old specimens can be especially valuable.
08:27This is the oldest specimen we have in the amphibian and reptile collection.
08:31Sarah has even developed a technique for recovering DNA stuck inside them.
08:36The process is similar to getting DNA from fresh tissue, with a little extra work.
08:41That extra work includes heating it up real high and trying to digest it and pull the
08:46DNA away from the formalin over a much longer period of time.
08:51But it can be hit or miss.
08:52It could be anywhere between 0% success all the way up to like maybe 60 or 70% success.
08:59If all you have is a 100-year-old snake in a jar, you might as well give it a shot.
09:05Like library books, some of these jars can sit untouched on their shelves for years.
09:10But all it takes is a curious person to crack one open and our understanding of the natural
09:15world can completely change.
09:18I always think whether it's DNA, whether it's taking the whole specimen to preserve, this
09:22thing then didn't just die in vain.
09:24It lives on in science forever.