- Hi there, I'm Frank Graff.

Discover the mystery of a zombie fish and why its feedback system matters, why we should return a special snail to the wild, and solving a dino death mystery millions of years in the making.

You'll be amazed by nature's wonders next on Sci NC.

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[gentle music] - Hi, again, and welcome to Sci NC.

You know snails are part of our vocabulary, how many times have you heard the phrase, moving along at a snail's pace?

Yes, the creatures are small and slow, but they are part of healthy systems across the world.

Producer Michelle Watker shows us how scientists hope to reintroduce one special species of snail from captivity back to the wilds of North Carolina.

- [Michelle] This pond might not look like much, but it's the site of the first step in restoring a magnificent species to the wild.

Meet the magnificent rams horn snail.

- Okay, bye guy.

Good luck.

Buena suerte, in case you don't speak English.

- [Michelle] But to understand why this is such an exciting moment, we need to travel back to where these snails came from because they've been on quite a journey.

Here at the hatchery in Marian, North Carolina, there's a team of biologists raising these little snails with a big name.

- I don't know exactly why they chose magnificent rams horn, it's quite large compared to other snails and it's really beautiful.

It's got this kinda tan shell with leopard spots almost, and the body is this deep maroon color.

So, I just sorta like to think its magnificent when they saw it, they couldn't help but name it anything else.

- [Michelle] Also, they can crawl upside down on the surface of water.

And look at this cute little eye stalks.

- [Emilia] They're so cute.

[laughs] - [Michelle] The magnificent rams horn is endemic to North Carolina, meaning it's only known to live in one very specific area along the coast.

But the thing is, it hasn't been seen in the wild in almost 20 years.

- These snails actually don't live in the wild anymore, they're what we would call extrapolated.

They're not extinct because we keep them in captivity.

We have three captive populations in the State of North Carolina, in three separate areas to sort of safe-keep from anything happening and wiping them all out.

- [Michelle] And keeping them alive in aquariums is no easy task.

In 1992, biologist Andy Wood, rescued some of the last of these snails found in the wild, right before Hurricane Fran, and quickly discovered how sensitive they are to water quality.

- I knew, all right, this is the last place that it might exist, let's bring it into captivity, so I brought it into the aquarium where I worked at the time and had it set up in aquaculture tanks in the building, but the salt atmosphere of the building contaminated the water, the snails withdrew into their shells, I knew something was wrong.

So I immediately pulled them out, took them home, usurped our young son's little wading pool, and that began the magnificent rams horn recovery project.

- It's a very unique niche species and they have a very specific habitat requirement.

To reproduce successfully, they really need a pH between about six and eight.

They can go a little bit higher than that and the adults can tolerate lower than that, but the juveniles cannot.

- It has no salinity tolerance, so it can't handle any saltwater at all.

- [Michelle] Which means sea level rise has an impact on where the snail can live.

- They're endemic to the lower Cape Fear River Basin.

They've only been found in four mill ponds that we know of.

A couple centuries ago, people were heavily heavily interested in collecting shells of snails and mussels in the 18th, 19th century, it was a really popular hobby.

And a lot of our museum collections come from that time period because there's not a record of these animals in any other places in all of those collections, we're fairly confident that they weren't in other places, because they're so large and distinctive that they would've been picked up by those people for sure.

And so that makes them a really unique, little Carolina treasure so-to-speak.

- [Michelle] Poor water quality caused by nearby development, pollution, and encroaching sea level rise, has made some of the places they used to call home, uninhabitable.

But alongside Andy's efforts, state and federal biologists have stewarded captive populations of the magnificent rams horn, waiting for the day when they'll be able to return to the wild.

And that day is finally here.

But first, all of the snails being added to the pond are getting little numbered tags.

- We have these really tiny tags.

They are actually honey bee tags, so people used to tag their queen bees, and the goal is to just know which snails are our contribution to the wild, in which are naturally production.

They are super kinda gooey, they create a lot of slime.

- [Michelle] Emilia and the team are prepping 800 snails to introduce to the wild.

And speaking of the wild, an important part of this process was finding the perfect place to release them, because what they need to succeed is not easy to find in their historic range.

- We were really excited when we found this pond since it just gets run-off, it stays pretty neutral for the most part, and hopefully will provide a good habitat for them that's more stable over time.

- [Michelle] For years, the team has been monitoring water quality, adding plants and adjusting the pH of this pond to make it an ideal, magnificent rams horn habitat.

They've even added fenced areas to help the plants thrive and get the snails a head start before predators can get to them.

And there's a big reason that releasing the snails in this pond is a possibility.

The US Fish and Wildlife Service and North Carolina Wildlife Resources Commission are coming together under a safe harbor agreement to potentially return 21 endangered or potentially endangered aquatic species to the wild, including the magnificent rams horn snail.

- This is a really new approach to conservation.

The really neat thing about the agreement is that we can work with private and non-federal land owners.

They can enroll with us and then if they have habitat that is suitable for the species, they can become part of this conservation story with us.

It's the piece that we've been missing, the piece that we can work with the private citizens of North Carolina, to help us to recover species when they're already doing really good work.

- [Michelle] And since the magnificent rams horn snail requires a very specific habitat, being able to work with land owners that have that habitat on their property is a big win for this species.

After being chauffeured across the state in specially designated coolers, the snails are eased into their new home.

- We're gonna take the coolers down to the edge of the pond and we're going to start slowly adding a little bit of pond water into the coolers at a time to introduce the snails to the new water.

If we just threw the snails in there, it might shock them so much that it would kill them, so we just give them a little bit of time to adjust and get used to a new quality of the world around them.

- This is wickedly exciting.

- I've only been here for six months, but I've been at this pond every once a week for the last six months, sometimes more than once a week.

So, it feels good to finally have snails in the snail pond.

I'm getting emotional thinking about it a little bit.

It's just really exciting, they've been in captivity for so long, and for them to finally be free, albeit in a pond, but for them to have more space and more nutrients, fresh air, fresh water, it feels like where they're supposed to be, and so it feels really good to be a part of getting them back to where they're supposed to be.

This is the first reintroduction effort that we've done for this species, so we don't know for certain how they will do.

I think they just need a chance, they need a window and they haven't really had the opportunity and so I think we gave them an open window, I think they'll take full advantage of it.

- [Michelle] You can watch more Sci NC episodes anytime on our website or through the PBS streaming app.

- Now to the discovery of nature's feedback system.

Think about it, if you've injured yourself, you can look in a mirror or possibly look at the effected body part to confirm it, that is a feedback system.

This fish changes color to protect itself, but how does it know that it did it?

This is a hog fish and watch closely, it's gonna do something pretty magical.

- They would go from a stark white over sand to this striped pattern when they were approached, when they felt like they were in danger, maybe when they saw others in their own species.

And so, we know that they had this color change ability.

- [Frank] Watch again.

Much like a chameleon, the reef dwelling hog fish can toggle its skin color between white, brown, and a stripe pattern, in seconds.

What scientists didn't know is that a hog fish is a kind of zombie fish.

It can change color even after its dead.

- We harvested this fish and captured one fish, and I put it on the deck of my boat, and later when I returned to the boat, I picked up the fish and the side that had been facing the deck changed color, white, and took on a pattern that matched the texture of the deck.

It actually color changed, mimicked the environment that was beneath it.

And I immediately took a picture, so I have this old picture of me just standing on the boat, rope's in the way of this unbelievable color change, an animal matching a boat deck.

At the time, it made me think something extraordinary was happening about how the animals see the world.

We knew that they could change color, but what we didn't know was that they could do it postmortem, after they had died.

And then to change color to match something so artificial.

- [Frank] Hog fish utilize specialize cells, called chromatophores, which each contain red, yellow, or black pigments, to change color.

The fish changes color by shifting how the pigments are organized in the cell.

But to understand how hog fish pull off the after death color switch, the team first discovered that opsins, the same light detecting proteins found in human retinas are found in the hog fishes skin.

- The very same proteins that let you see blue light with your retina, is the same protein, this obsin, that is in the skin of the hog fish, all over the hog fish.

So we knew that a light detecting protein was in the skin.

- [Frank] But that discovery only deepened the mystery.

What were the opsins doing and why see through the skin when hog fish have a perfectly good set of eyes?

- Well, we found, we used this amazing method, where you can make proteins of interest glow.

So we took skin of hog fish, we cross-sectioned it, cut it in thin sections, we applied this marker to make our opsin glow so we could find where it was.

And surprisingly, instead of right on the surface of the skin, where maybe they'd be looking at the surrounding environment, we found this opsin buried beneath their color change cells, almost as if they had a camera pointed at the TV screen of their color change.

- [Frank] The opsins are those glowing cells, but the electron microscope revealed the opsins don't have a view of the world at all.

The proteins are packed into specialized cells under the chromatophores, the pigment cells that allow the hog fish to change color.

- This is a cross-section through the skin.

If light is passing from the outside, this is the outer most layer of the skin, so this is a bunch of epithelial cells.

And then we get to the chromatophore layer, so you see this black pigment, that's a chromatophore, and actually these smaller globs here, these are yellow or red chromatophores, so they're filled with yellow and red pigment.

And then, the green labeling, is right underneath these chromatphores.

- [Frank] Here's the key, while the pigments in the chromatophores change the outward facing color of the hog fish, the pigments also filter how much light reaches the opsin.

- So, the light is coming in from this direction, this would be the scale chromatophore and then photo receptor.

So, it is capturing light in a similar way to the cones and rounds of your eye but it's not using that for image formation, it might be, it's using that for the feedback systems.

- [Frank] In effect, the opsin is able to see what color the fish is, from the inside.

- Basically, when the animals have a dark pattern over their body, the pigment is dispersed in these color chain cells.

It blocks the blue light needed by the opsin to be activated, shuts them off.

But when the animals turn white or take on this lighter pattern of the body, the pigment of these cells gets out of the way, the blue light can pass by and turn the cells on.

In this way, we had this whole shift of perspective.

Maybe the animals aren't using this skin vision to watch their surroundings, but rather to watch themselves, to know what color they are if they're performing color change correcting.

- [Frank] The working hypothesis then is that the hog fish doesn't use its skin vision to watch its surroundings, it's using it to watch itself.

A way to double-check what's happening.

- For a fish that has to color change for survival, perhaps to camouflage in its environment, it needs to be completely sure that it is color changed correctly.

The eyes, of course, you have beautiful detecting system on the face, the eyes image the surrounding environment, telling the animal you need to color change, you need to accomplish white, you need to accomplish a stripe.

But the skin vision is watching itself to make sure it did that command correctly.

Why that's so cool is not just an answer for hog fish, but virtually every color changing animals, from octopuses to reptiles, amphibians, and fishes, we just keep making these discoveries that they can detect light with the skin.

Look how whimsical it is, look how mysterious it is, and this is something worth exploring.

- [Michelle] Check out our weekly science blog to take a deeper dive on current science topics.

- Entomologist Adrian Smith, at the North Carolina Museum of Natural Sciences has taught us about some amazing insects thanks to his super slow motion videos.

But Smith admits the bat fly the most unusual insect he has ever photographed.

- [Adrian] This is hands down the weirdest insect I've ever filmed.

Believe it or not, this thing is a fly.

Like, a fly as in an insect in the same group as your standard house fly or fruit fly.

But this fly doesn't have wings and it barely even has a recognizable head.

The weirdest thing about it is where it lives and where I found it.

I collected it off a bat.

It's an ectoparasite of bats commonly called, a bat fly.

I had assumed bat flies were only found in the tropics, but when I realized we had them here in North Carolina, they immediately went to the top of my list of bugs I needed to see.

Luckily, one of my colleagues here is a bat expert, and my best chance of seeing them was going out in the field with her.

So, let me introduce you to Lisa and her work.

- I am the mammal collector manager here for the North Carolina Museum of Natural Sciences, and my job is to maintain, provide, care for our research collection of mammals.

Our collection currently has about 25,000 specimens and those include scientific study scans, skeletal material, and tissues.

In these cases, actually the four, set of four cases, it has all of the species of bats that are found in the Southeastern United States.

Besides maintaining this mammal research collection, part of my job entails going out into the field and monitoring and tagging bats in the state and in the Southeast.

So, we chose this particular site to put our nets, because we have the branches over the road, and what we hope to do is close off this funnel where bats would be flying down the road under the tree limbs.

And they can see the net, they can detect it with echolocation, but we are successful in catching them because they're not looking for the nets, because they use this road all the time, this is one of their normal routes.

Every 10 minutes throughout the night, we'll come check the nets, any bats that are in 'em, we'll extract, take 'em back to our little table and work them up.

We'll give 'em a band with a unique number on it, and then subsequent years when we come here and net again, we might catch some of these banded bats.

That's how we know about longevity in bats is by recapturing and find out that they were banded 30 years prior.

We know that bats live very long time because of the banding practice, so it's really useful information for us.

We hope that we might find a bat or so with bat flies on them.

We have found them here actually last year, so we're hoping that maybe we can relieve a bat of an ectoparasite.

- So we did find a couple bat flies and I had assumed they'd be dug down into the bat's fur kinda latched in like a tic.

That was totally wrong.

So here's what it looked like on a bat in the field.

The arrow is pointing one out.

What we saw was they were in constant motion and nearly impossible to film.

And here it is again, this one's gonna crawl into the bat's ear and up and around its head.

So you see how fast they are.

To se how they were moving, I had to bring one back here and film it up close and in slow motion.

Everything you're about to see now was filmed at 600 frames per second, so what you're seeing is about 20x slower than real life.

So, the first odd thing about them is the way they walk.

They use a standard tripod insect gate, but each step starts with a high kick throwing the front legs up as high as they'll go.

Their legs and their body are specialized for clinging to the fur of a bat's body.

And looking up close at the end of their legs at their tarsal claws, it's pretty cool how you can see them retract and fold up when the fly goes to take a step.

Now, the head of the fly is this structure.

It's between the front legs and held straight up over the body.

The fly uses it to take blood meals from the bat it lives on.

Looking at it up close, you can see how most recognizable fly head structures are dramatically reduced.

One bit of anatomy that's recognizable as being fly-like are these, the halteres, I was surprised to learn that bat flies even had these, because in more normal looking flies like this one, halteres are these, behind wings that have evolved into flapping gyroscopes, leading along with every wing beat and helping the fly orient during flight.

With the bat fly, if you look right here, you can see the blurred motion of the halteres being rapidly flapped up and down.

The fact that they still have functional flapping halteres but have completely lost their front wings and their ability to fly, is incredible to me.

Here's a shot where the halteres can be seen flapping while the fly is walking, and then remain in motion here when it comes to a stop.

Another weird behavior I filmed was this.

When I breathed or slightly blew on the flies, they responded by doing this, stretching their front legs high into the air.

It reminded me of a behavior that tics do, called questing, where they hang out on grass leaves with their front legs outstretched ready to grab ahold of whoever walks by.

Maybe the bat flies were doing this as a general response to sensing mammal breath.

They were probably hoping that I was a bat they could climb back onto.

So there are nearly 300 species of bat flies and there's a bunch more interesting things about them, but for now, that's what I could capture.

Thanks for watching.

- [Frank] Want more Sci NC, you can find these stories and more on our YouTube channel.

Like and subscribe.

The age of dinosaurs may have ended more than 65 million years ago, but a fight between two dinosaurs lives on in a fossilized tyrannosaurus and triceratops interlocked in what looks like a battle.

The fight has North Carolina researchers puzzled and their search for answers is the centerpiece of a new exhibit at the North Carolina Museum of Natural Sciences.

Producer Emmy Trevitt explains.

- [Emmy] Bit by bit, paleontologists hope a 67 million year old mystery would be finally solved.

- [Lindsay] These particular specimens are even more fascinating than your average dinosaur.

- [Emmy] Scientists call them the dueling dinosaurs.

This is a model of the fossil made up of two famous dinosaurs, the tyrannosaur and triceratops.

And what's fascinating is that they were found intertwined here in the Hull Creek formation of Montana.

It's an arid moonscape now but back in the cretaceous period when the dinosaurs roamed, it was an inland sea.

Researchers are drawn here by the wealth of fossils under its surface, including our dueling dinosaurs.

And that's the mystery, were the dueling dinosaurs actually dueling?

And why were they buried together?

And now, they're at the NC Museum of Natural Science, where Dr. Lindsay Zanno and a team of researches try to decipher this mysterious fossil.

They have their theories about how the pair may have wound up together.

- [Lindsay] That one day, could've been fighting, maybe the triceratops was dead and a pack of these tyrannosaurs came in and they got angry at each other and one knocked one off.

Maybe a big flood or storm or a natural disaster killed them and then swept their bodies together.

- [Emmy] But they can't yet confirm any of these for sure.

What they do know is that there were several species of tyrannosaur and triceratops from the cretaceous period, living in the Hull Creek area at the time.

With the triceratops, they need to decide which one of the two or three species their skeleton could be.

But the tyrannosaur leaves a larger question unanswered.

- It's just breathtaking, it almost looks like he could just stand right up outta the rock.

This is almost the entire body of the tyrannosaur.

We've removed the skull, it's already under study.

We also have brand new questions about tyrannosaurs that are part of long standing controversies over what these small bodied tyrannosaurs actually represent.

Are they juveniles of bigger species or are they just smaller bodied species of their own?

- [Emmy] And as they piece together the puzzle, they use a bit of science to piece together the bones.

The team uses reversible glue to reconnect the tyrannosaur to part of its hip.

- And the nice thing is, if we discover other pieces and we need to take this piece off, I can just apply acetone back on there and it'll pop right back off.

- [Emmy] And these researchers use histology, the study of bone microstructure, to estimate how old the animal was when it died.

- So there's a lot of different things that you can tell from the bone structure and that's why we actually will go ahead and cut some of the bones.

This block right here is the main body of our tyrannosaur.

You've got a beautiful articulated foot, so it's just like it would've been the animal when it was alive, all the way down to these tips of the claws, going up here to the ankle, then back to the shin, the femur, the upper bone would've been here.

We've got the hips there.

So that's what makes these animals so amazing is that they just have this beautiful articulation in just how it was in the body, and that can tell us a lot of information.

- [Emmy] Beyond how they were found, these fossils are even more intriguing, because there's more to the fossil than just the bone.

- [Lindsay] When you have an animal that was buried as a carcass with all of its soft tissue on, with its muscles and its organs, it gives you the opportunity to learn so much more about the biology of a dinosaur, than you could if you just found its scattered, broken remains.

- [Emmy] It's a slow process, decay, fossilization, the waiting to be found, and researchers have been up until this year, patiently waiting to dig for answers.

- We've decided to make the process of science transparent to the public in a completely new way and invite people to come inside a real working science lab, talk to the scientific team everyday about what's happening, and just experience it, the authenticity of being in a research environment.

- And I'm Frank Graff, thanks for watching.

[gentle music] - [Narrator] Quality public television is made possible through the financial contributions of viewers like you who invite you to join them in supporting PBS NC.