How scientists captured a stunning, hellish menagerie of half-dissolved creatures

A new imaging strategy is responsible for capturing a hellish menagerie of creatures: a skeletal frog that’s crawling out of the frame, a dead red fish that stares back at you, and a crouching shrew with a cavernous, empty ribcage. How did scientists take these shots? By making them glow red and by essentially embedding some of them, like the fish, in Jell-O.

Scientists have been imaging skeletons for decades by stripping dead creatures of their flesh, staining the bones red and the cartilage blue to highlight them, and snapping a picture. Studying the anatomy can help researchers figure out how different organisms are related and how the creatures move the way they do. The trouble with these old-school techniques is that they can make it hard to pose specimens to take clear pictures of complex joints, for example, when that specimen is essentially skin, bones, and some connective tissue. W. Leo Smith, an associate professor of ecology and evolution at the University of Kansas whose lab photographed these creatures, describes the specimens’ consistency as like “mushy, spoiled lettuce.”

This new technique, which Smith’s group recently published in the journal Copeia, gives scientists a way to pose those floppy, de-fleshed bones by embedding them in gelatin, the stuff that turns Jell-O from a liquid into a wobbly goo. Perfected by grad student Matt Girard and Chesney Buck, an intern in the lab with an interest in taxidermy, the gelatin congeals around the skeleton of the fish or the seahorse and lizard (below). After the photo op, it washes away without harming the specimen. The team also discovered that a red dye they were already using to stain bones actually fluoresces under a high-energy blue light. That’s what gives the images that crisp, creepy red glow.

“In the proverbial, ‘A picture is worth a thousand words’ way, these things really help illustrate certain characteristics,” says Smith, who is also a curator at the University of Kansas Biodiversity Institute & Natural History Museum. The strategy, for example, can capture how exactly fish jaws move or highlight the gaps and connections between bones. “That may not sound like too big a deal, but when you’re trying to figure out how one group of fishes is related to another, those little gaps end up being a lot of the characters,” he says.

The Verge spoke to Smith about de-fleshed fish, skeletal Jell-O salads, and how he accidentally gave himself Smurf hands.

This interview has been edited for clarity and brevity.

Why are you taking pictures of skeletons?

A lot of people who look at these are trying to figure out how different organisms are related to each other. Some people do that with DNA, some people do it with anatomical specimens, some people do that with extinct specimens like paleontologists, and some people mix all of these things together. There’s a handful of us in the fish world that try and mix the genetic, the living, and the fossil specimens together to put all of that into the tree of life. That helps us figure out how old things are by incorporating the fossils and how everything’s related.

Walk me through how you go about creating these images

We go through this process called clearing and staining, which is a way of making a skeleton. We dehydrate the specimen in a lot of alcohol, and then we stain the cartilage blue. We put it in a mix of acetic acid and ethanol. So it’s just like an Easter egg where you put it in vinegar and a dye, and it stains the shell blue.

How does that smell?

It’s really strong. I was once shaking a jar of it to mix it and the jar broke in my hands, and they were semi-permanently stained blue like a Smurf, and the acid peeled everything away. It was like two to three days before the smell went away.

What’s the next step?

Then we use stomach enzymes from a cow to digest away all the muscle, which makes the fish fairly transparent. It certainly removes all the fleshy parts. And then we stain the bone red, and we put it into glycerine, which is this gross, highly viscous solution that’s kind of like corn syrup. So what we have when we’re done with that process is a specimen where all the skin and connective tissue and nerves are still there. But all the muscle is gone, so it’s kind of see-through. It’s basically like something from a Scooby Doo cartoon where they rip the skeleton out of something and there’s just the skin left. It’s real flappy and flaccid and doesn’t have any strength.

These are old-school procedures, right? What are the advances from your group?

Those techniques were developed about 40, 50 years ago. So that part’s not new. But the problem with that is that you can’t really pose them. There is something beautiful about going to a museum and seeing a T. rex. You can pose it, you can do a scary scene where it’s eating a smaller lizard. But we can’t do that with these things. These things are just dilapidated. They’re really just like mush.

So I’ve been trying to figure out a way to be able to pose them forever. One of the things I wanted to do was figure out a way to basically embed them in something. We tried bunch of different chemicals, and basically, in the end, we settled on gelatin mixed with the glycerine. And we could pose them however we wanted. It’s a little tedious, it takes a lot of time for the best ones. You just sit there with two forceps under a microscope and hold the thing while the gelatin hardens. If you mess up you have to start all over.

So it’s basically like a skeletal Jell-O salad?

Yeah! And it’s fun. It works really well for what we’re trying to do. And it does wash away. So you put it in this thing, and you’re like, “Well how safe is it for these specimens,” right? Because some of them are rare. And so we tried a lot of different things. We cleared and stained a bunch of goldfish and left them out and it looks like there’s no long-term damage, as far as we can tell.

What about the colors?

The luck part came in where, for whatever reason, I stuck one of these [cleared and stained] fish under the scope. Nobody had ever really noticed that the red that we dye the fish with fluoresces red really bright under a blue light.

So what’s cool about it, and the reason it really works, is that the filters on the microscope or on the camera filters out every other color. You’re only getting this very specific wavelength of the fluorescent dye. So it removes everything else, so you get these very pure images where just the bone is highlighted and it really makes the bone stand out against other pieces of bone. It really just clarifies and makes all the edges crisp. It’s just very pure.

How do you take the pictures?

For the photos themselves, we [can] put it under a microscope that’s already set up for red fluorescence, and there’s nothing to it other than looking through the microscope. But because most of these fish are the size of your hand and you can’t see them under a microscope very easily, we have to take a picture using a regular old camera. And so we illuminate the specimens. We tend to use these diving flashlights that emit a very particular blue light that’s like a blacklight on steroids. It’s at the wavelength that will illuminate the dye.

And then you need somehow to filter out everything else. You’re basically trying to get a filter that will block out most of the light but that will allow the fluorescent light to come through. You can buy actual camera filters for it, but most of them aren’t strong enough for the pictures. So we’ve used dive masks. Dentists, when they’re hardening different things in your mouth, they will use a UV light. So you can buy the shields they use to protect their eyes. We use those and either hold them to the camera lens or attach it to the camera with a bungee cord so we can walk around with it. And then we just take a picture. The picture part is really easy.

Which one is your favorite?

My favorite one is the Pacific spiny lumpsucker picture. They’re normally a really cute fish in the Pacific Northwest in the Seattle area up to Alaska. Their pelvic fins have been modified into a sucking disk. So they normally are just real cute, but somehow they look really creepy when you do this because their bodies are covered in these modified scales that just look like volcanoes all over their bodies.

I was trying to get the one shot that emphasized the value of a head-on shot. So I took a bunch of pictures of fish head-on, with their mouths open — because every ichthyologist would love to have this. And all of a sudden it hits you that that’s the one to do. I like that one because it was useful for it to be posed in the gelatin, I think the picture came out really well. That’s the one I put on my wall in my office.

And which one haunts your nightmares?

The shrew is probably the one that haunts my nightmares, because that one is really creepy. The mammalogist didn’t like it because he thought it looked like too much like a small human just sitting there. That’s the one that freaks me out the most. My student took that one so it doesn’t bother me as much because I didn’t have to look at it when he took the picture.