Science Friday - Inside The Race To Save Honeybees From Parasitic Mites

Episode Date: July 30, 2024

Last year, almost half of the honeybee colonies in the U.S. died, making it the second deadliest year for honeybees on record. The main culprit wasn’t climate change, starvation, or even pesticides, but a parasite: Varroa destructor.“The name for this parasite is a very Transformer-y sounding name, but … these Varroa destructor mites have earned this name. It’s not melodramatic by any means. [They are] incredibly destructive organisms,” says Dr. Sammy Ramsey, entomologist at the University of Colorado Boulder.These tiny mites feed on the bees and make them susceptible to other threats like diseases and pesticides. They’re also highly contagious: They arrived in the US in 1987, and now they live in almost every honeybee colony in the country. Honeybees pollinate many important crops, like apples, peaches, and berries, and their pollinator services add up to billions of dollars.Ramsey and his lab are trying to put an end to the varroa mites’ spree. Part of their research includes spying on baby bees and their accompanying mites to learn how the parasites feed on the bees and whether there’s a way to disrupt that process.In Boulder, Colorado, SciFri producer Rasha Aridi speaks with Dr. Ramsey and fellow entomologist Dr. Madison Sankovitz about how the varroa mites terrorize bees so effectively, and what it would take to get ahead of them.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

A pesky little parasite is decimating honeybee populations by feasting on their guts. So these Varroa destructor mites have earned this name. It's not melodramatic by any means. They are incredibly destructive organisms. We lose between a third and half of our bee colonies, like nationally, every year. It's Tuesday, July 30th, and this is Science Friday. I'm SciFry producer Charles Burgquist. Now, in the peak of the summer, honeybees are busy collecting pollen, making honey and

preparing for the winter ahead. And if you're a beekeeper, you're hopefully eyeing a sweet, sweet harvest of honey. But there's one thing you don't want to find in your hives, gnarly little mites. Last year, sci-fry producer, Rasha Arredi, went out to Boulder, Colorado to learn more. As you said, there's a teeny tiny mite that is absolutely wreaking havoc on honeybee populations. I went out to Colorado and I met Dr. Sammy Ramsey, an entomologist at CU Boulder and his team of be experts. They're working on studying this mite, so they hopefully one day can take it down. I met them in this beautiful field, nestled among boulders, rolling hills. Right off the main road, there were around 15 beehives, all lined up next to each other. And we were going parasite hunting.

The name for this parasite is a very transformery sounding name, but it's actually called Veroa Destructor. So these Varroa Destructor mites have earned this name. It's not melodramatic, any means, they are incredibly destructive organisms. We lose between a third and half of our bee colonies, like nationally, every year. Because of these mice? The primary driving factor is Varroa destructor. There are other things that are going on, and I don't want to make it seem like there is a single problem, it's multifactorial, but what we do know is that these parasites are

at the center of the web of problems. Because pesticides are one issue, but because the parasite literally feeds on the tissue that breaks down pesticides, pesticides are a lot. more deadly when they are around. In addition to that, poor nutrition is a big issue for bees, but it becomes a huger issue when they feed on the tissue that stores excess nutrition and allows them to get through these dearths in their nutritional context. So the mites eat the bee stomach, like a smoothie, a bee smoothie? It is actually a bee smoothie in a lot of ways. So it's referred to as the fat body, and the fat

body does the job of the liver of the bee. It's a part of their endocrine system. It regulates their hormones. It regulates their immune system. and it also stores nutrients and regulates their metabolism. In addition to all of that, you can't eat normal stuff because if there's any toxic component to it, you can't break it down. So it wouldn't kill the bees as much as make their lives miserable? It makes their lives miserable enough

that oftentimes they die as a result, especially from viruses that they come in contact with. The tough part now is that when colonies start collapsing, the bees that lived inside of those colonies, that no longer have a place to live will begin to drift to any nearby colonies that they can go to. And the worst part about that is the mites that you get under those circumstances

are likely to be a lot more virulent. Just like there are different strains of COVID-19 that can cause all kinds of issues, there are more virulent strains of varroa. The ones that kill a colony and then their bees fly over to yours and then deposit their mites there, those are typically more virulent mites.

Oh, no. Yeah. These mites are too good. They are. And I mean, honestly, it's not just that the mites are too good. It's that the bees have never dealt with something like this before. Our honeybee is not native to the U.S. It evolved in Europe and colonists brought the species over with them. The Varroa mites, on the other hand, evolved in Southeast Asia. The bees over there can deal with the mites pretty well. But the European honeybees can't. They didn't evolve to, which makes them very susceptible to infestations. what about the native bees? They also wouldn't have encountered

these evil little mites, right? The good thing about these evil little mites, if I can say that there's a good thing about them, these mites are very species specific. They have attuned themselves to the life cycle of the bees, to the exact timeline of the bees, to the endocrine system of the bees,

the different levels of hormones and things, and so they can't just offload themselves into a bumblebee colony and expect that they're going to be successful. We have never seen them reproducing in bumblebees, and wasps, even though sometimes they'll accidentally end up in one of those colonies. They just can't seem to make it work.

Ah, so those other bees just kind of lucked out. They did luck out. The problem is there's another parasite currently spreading around the world that is related to Varroa destructor, but its populations grow much more quickly, and it is the least species specific. No. Yes. It's called the tropemite.

My research is divided between varroa mites in the U.S., and then I go to Asia for about three months every year and study the tropemites there, because my goal is to make sure we don't take our eye off the ball. Now that I know exactly what we're dealing with, we're ready to open up a hive. During the height of the summer, there's thousands upon thousands of these little hexagonal cells in the colony that have a developing baby bee inside.

The queen lays an egg. In a matter of days, that egg hatches turns into a larva, that larva spends a few days developing into a pupa. And it's at this stage right before it turns into a pupa where the parasite jumps inside. Now the bees try to put a layer of wax over the cell to stop parasites from getting in there. And the parasites have learned what the larva smells like

right before it's about to get capped. So they have totally outsmarted the bees and learned to jump in and instead of the cap protecting the larva from the parasite, it protects the parasite from the bees and from our pesticides. Inside the hive that Samia wanted to crack open, there were around 20,000 bees,

which is a fairly small colony. And for the bees to let us in, we had to distract them. All right, ladies, when we pump this smoke at them, they start sticking their heads inside of the cells and consuming honey because it mimics the experience of there being a forest fire in the area. The behavior that they then have under that set of circumstances

is we should probably consume as much of the honey as we can, store it in our honey stomachs, because we're gonna have to fly off with it if this fire gets too close to us. And so it gives them something else to worry about as top priority instead of you. instead of you. All right, ladies, let's see what's happening with your babies.

Let me see if I can get a nice little frame out here for you. And then it was time to shake off the bees, shoe them away so that we could take a closer look at the cells and try to find some with baby honeybees that could be carrying the varroa nights. So I've taken to like counting the three in random languages when I do this. Nice.

What language are we getting today? Uh, Japanese. 1, 2, 3. Alright. Oh, wow, this frame might be the one. By the one, Sammy means a hive full of varroa mites. There's a varroa mite sitting right on the body of this bee. Right there, that red bump that's on the back of the bee.

It looks like a little bug pimple. It does look like a little bug pimple. This little bug pimple is unfortunately mobile. And if it were a pimple, proportionally it would be the size of the bee. of your hand. What? Yes. It's one of the largest external parasite body ratios that we see in the scientific world.

So at this point, right in front of us is a tray that looks like a giant sheet of honeycomb. There are bees ducking in and out of the tiny, sticky hexagonal cells. Some of these cells, like the rim of the cell is just a little bit higher up than it is in the others. And those are cells where the larvae has finally reached the age where they are teenagers. teenagers, and so they've reached a point where they are about to be capped and the parasites know this. The cells that are capped or covered with wax kind of look like someone shoved a yellow crayon through them.

We can't see inside, so we have no idea if there's any unlucky baby bees with varomites chewing on them. And so we're going to grab some of them. We're going to take them to the lab and we're going to hope that if there are parasites inside the cell, we can transfer them into our imaging system. Normally what goes on under these cell cappings is not quite a mystery to us, but it's very hard for us to actually discern because it's pitch black inside of the colony. So you can't see anything and it's too small to get a camera inside.

We've created these artificial cells in the lab that are made of beeswax, but two of the walls of the hexagon is replaced with high optical clarity glass. So you can actually position them in an incubator that I've designed to have a microscope and a camera over it. And then you can watch what the parasites are doing inside of the cell. instead of what we used to do where we would just open the cell at random intervals and say, okay, that's what they were doing at, you know, two hours in, at five hours in, at three days in, at ten days in. Now we get to watch the entire process start to finish.

So if you want to see the next part of this process, we're going to head back to the lab and see you Boulder, the Boulder Bee Lab. Let's do it. Let's do it. I'm excited. Sammy and his team packed up a couple frames from the beehives into a carrier. It looked like a briefcase full of honeycomb. We drove over to Sammy's lab to get a close-up view to see how exactly he can spy on baby bees and what he can learn from doing so. So we have just arrived in the Boulder Bee Lab and now the hands-on part of actually moving the mites into these cells gets to be conducted. Sammy and his team started by taking out one of the frames that we brought with us in the bee briefcase. They propped it up on a stand so that they could see every little little

cell, and they opened up each cap cell very tediously one by one by one to see if any of the babies nestled inside of them had mites feeding on their guts. So we're going to lift the bee up, look for the mite, and then if that bee has a mite, we're going to transfer the mite, the brood food, and the bee into one of our artificial cells. Dr. Madison Sankovitz, a postdoc in Sammy's lab, showed me how to do this. So I'm going to use these shirt. forceps to open up one of these cells so I can kind of cut around the wax capping. It looks like earwax. Oh, yeah, it is essentially ear wax.

So close, so close. There's this little baby bee. I'm pulling out of here. It looks like a little grub or to be cranked like a bugger. Totally, yes. Grubbs slash booger. Both are acceptable. And then some arroa mite in this cell. We hit the jackpot.

This particular bee is going to become an experiment. She's going to survive. But unfortunately, the parasite that was already inside of this cell with her is just going to continue doing what it would have done otherwise under our watchful eyes. So no bees will be murdered in the making of this cell unless the mite murders them. And then that will unfortunately be a data point. That boogery bee will get packed into a little glass chamber. It kind of looks like the very top of a mechanical pencil.

And inside its little room, it has everything it needs. Baby food, a bed of wax, and, of course, a varroa mite. So because I want to keep this system as natural as possible, I'm taking the cap off of a cell that was just capped by a bee. And so if there are any potential pheromones or things that these mites need to smell in this process, I'm going to make sure that they do that. So putting the cap on here. So the goal is like neither the bee or the mite really notice that they are not in hive anymore.

That is exactly the goal. and it is a hard goal to pull off because honeybees work so hard to make that hive such a distinct home. Once the bee is tucked into its little cell, it gets placed into a one-of-a-kind imaging machine. It maintains perfect humidity and heat and has cameras that spy on the bees for about 10 days as they go from a slimy-looking larva to a beautiful honeybee. Sammy and his team call it the mite insect. system. What do you learn from spying on them and watching them do this and invading all of their privacy? I am invading their privacy, and it's very important that I do so because before when

people wanted to see what was going on with the mites, they had to open individual cells after a certain amount of time, and the influx of air into the cell lets the mite know the jig is up. They know I'm here, and they stopped doing all the things they were doing before. They stopped reproducing. They will sometimes continue to feed, but most of the time they'll just try to get out of the cell. At that point, you've created a stop motion system where you can tell what was going on the moment you opened the cell, but before and after is a mystery. Well, I'm tired of those mysteries. I want to see everything that happens here, and I want to be able to catalog all the different behaviors and how long they're doing each thing and discover if there are any potentially weak links in their life

cycle. And so what we end up doing here is by filming all 10 days that they're running around down here inside of the cell, we have the opportunity to really see all the different things that they're doing and actually catalog all of it and turn it into a data set. For example, Sammy can see if and how a baby honeybee could take down a mite. One way the bees do this is with silk, which they use to build their cocoons. If the bee picks up on a mite, it'll go into a frenzy and bolts that mite down to the bottom of the cell using silk fibers. The key is, you know, for the bee to do this before the mite latches on. It only takes like three or four silk fibers, and that mite can't get up anymore.

And so I'm wondering, is there a way that we can jumpstart that ability and kind of more strongly encourage them to do this really fast? Because if they can outsmart the mites at this stage of the life cycle, they can stop them from hopping on their face and doing all the nefarious things they do during the rest of the time these bees are in the cell. Watching the mites chow down on the bees in the imaging system also gives Sammy and his team insights into how the mite keeps itself alive. Oh, do you see that varroa mite running around in there? So both mites survived, but did not reproduce.

Why? All right. So here's the thing. There is a infertility rate in colonies that ranges wildly, and we don't know why. The last paper I read it by was like between 8 and 62% in the study that they did. Like the mites will go into the cell, do their fairly normal behaviors of feeding, but then just for whatever reason, choose not to reproduce. Don't know what's up. Sometimes I will talk about these mites being clever, being fascinating, being interesting, and people bristle at that.

But my interest in these mites, my ability to peer into their life cycle and learn about them, it is really, really, really important for us being able to find out the weak links in their life cycle, us being able to find out the weak links in their life cycle, us being able to find. out how to disrupt their capacity to exploit the bees. If we don't understand them, we can't accomplish any of that. And this imaging system gets really detailed photos and videos of the mites feasting on the baby honeybees' insides. To the point that we can even see their mouth parts move. Sammy walked us over to a computer to show us very close up what goes on in the little bee chambers. Ha ha! Check this one out.

That is a varroa mite with its mouth parts embedded in the fa. in the fat body tissue of the bee. So all this squishy white stuff that you see here, this is the bee's liver. So you can actually see this mite embedding its mouth parts in this bee. It's a whack-a-doodle. All this brings us to one last question.

How do we beat the Varroa destructor mites? That's a great question. This parasite is now officially a cosmopolitan parasite. It is present pretty much everywhere bees are kept. So we're going to do everything we can to understand them because in order to beat them, we've got to figure them out. When you're looking at things and you don't know what you're looking for, that some of the best science happens,

we're not looking for anything specific. We're just looking to understand them better than they've been understood previously. And then it's possible that something will present itself. We don't know if it'll be a spray. We don't know if it'll be gene drive or some sort of double-stranded RNA disruption of their genetic code. We don't know yet. But we're going to figure that out by intensely studying the,

these organisms learning about their reproduction, their feeding, their digestion, their entire life cycle, and then we'll know what options are available to us. A huge thanks to Dr. Sammy Ramsey, Dr. Madison Sankovitz, and Christopher Borky for speaking with me. I'm Rasha Aridi. Lots of folks help make this show happen, including Dee Petersman, Sandy Roberts, Shoshana Bucksbaum. On tomorrow's episode, How Advances in Battery Tech could help the world meet green energy goals. Join us. I'm SciFri producer Charles Berkwist. Thanks for listening. We'll see you soon.