Bumblebee Queens Can Breathe Underwater — And Scientists Just Figured Out How

Speaker A:

Welcome back to Secret Pollinators.

I'm your host, Kelly Parks. And today's episode starts with a lab accident.

Isn't that crazy?

Well,

it's 2021, and researcher Sabrina Rondeau is at the University of Guelph studying how pesticide residue affects hibernating bumblebee queens.

And that's important research.

Well,

the queens are tucked into soil filled vials in a refrigerator,

which perfectly mimics their underground winter burrows, because, remember,

bumblebee queens burrow underground.

And that's partly why bumblebees are my favorite pollinator.

Anyways,

the refrigerator malfunctions,

condensation floods four of the vials.

Rondeau goes to check out the damage.

And guess what? The queens are still alive.

And that accident just changed what we know about bumblebee survival.

And this is the exciting part for me and hopefully for you.

A new paper published this week in the Proceedings of the Royal Society Bee finally tells us how the setup,

why this matters.

Here's something most people don't realize.

Over 80% of native bee species,

including most bumblebees, nest underground.

Bumblebee queens spend six to nine months down there in diapause, which is,

you know, basically like insect hibernation.

Their metabolism drops by 99%,

and I would say they are, for all practical purposes,

in suspended animation.

So the ground floods,

you know, there's snow melt, heavy rain,

rising water tables,

even your garden hose turned on.

A hibernating bumblebee queen has zero ability to respond to an emergency.

I mean, she can't move,

she can't flee.

She just has to survive whatever happens around her in her little burrow.

And so what does happen when her little burrow fills with water?

Well, as it turns out, not much.

She's fine.

Usually.

After the accidental discovery, Rondeau ran a formal experiment with 143 Bumblebee queens fully submerged in cold hibernation temperatures for up to eight days.

90% survived.

So the question was never if they could survive.

I mean, that was kind of always my question.

But the new question is,

how do they survive?

The science,

three tricks in one. Bee researcher Charles Darvo at the University of Ottawa did the math. First,

if a bumblebee queen is holding her breath underwater for a week,

she'd need 20 milliliters of oxygen stored in her body.

Well, she's one millimeter in volume.

So in his words,

it was impossible,

which meant she wasn't really holding her breath at all.

So using precision respirometry equipment,

which is equipment that Measures gases moving in and out at incredibly small scales.

Darvo's team submerged queens and watched what happened.

Oxygen in the water dropped and carbon dioxide continuously released into the water.

So believe it or not, she was breathing underwater the whole time.

That just blows my mind.

And here's how the researchers think it works.

And this is truly where it gets wild.

Many aquatic insects trap a thin pocket of air against their bodies,

and it acts like a physical gill.

Oxygen from the surrounding water diffuses in and carbon dioxide escapes out.

And scientists call that plastron.

Bumblebees are covered in dense, fuzzy hair,

and that hair most almost,

or almost certainly traps an air layer in the same way.

It's just so hard to believe.

So a land bee with functional gills hidden in her fur.

And that's not even the whole story.

The team also found elevated lactic acid in the submerged queens,

the chemical signature of anaerobic metabolism.

So she's also producing energy without oxygen as a backup system.

And her already slowed metabolism drops even further when she's submerged in water.

And it's so far that the tiniest trickle of available oxygen is enough to keep her alive.

So three strategies running simultaneously. Underwater respiration,

anaerobic backup, and profound metabolic depression.

Wow.

And Dr. Darvo put it perfectly.

The whole combination of strategies is the most fascinating aspect of this study.

And I've got to tell you,

I couldn't agree more.

The recovery and the bigger question.

So when bumblebee queens come back up for air,

they don't just pop right back to normal for several days. They breathe at a higher rate than queens who are never submerged.

And their bodies are basically clearing out that lactic acid backlog.

So they need time to recover.

And that is where this gets complicated for conservation.

With intensifying storm events and flooding, researchers are now asking,

how many times can a bumblebee queen go through this one flood she can handle,

but her hibernation energy reserves are finite. She has to emerge in spring with enough fuel to start an entire colony alone.

And every submersion burns resources.

So at some point,

like Dr. Darvo says, there might be some point of no return.

And we don't know where that point is yet.

And that's what comes next and is so incredibly fascinating and information that we really need to know for conservation.

So I'd love to know because I'm always curious,

for those of you in flood prone areas, have you thought about where your ground nesting bees are overwintering on your property?

Because slope matters,

Sandy. Well, drained soil matters. And the queens that survive are often the ones whose microhabitat keep them above the waterline.

And that's what I've learned in the last 20, 25 years at my ranch in Montana.

The bumblebees,

the queens,

they just know where to have their little burrows. It's incredible to me.

So if you're restoring pollinator habitat, you gotta consider topography,

that gentle slope,

native grasses with deep roots that help drainage.

These are small choices with enormous consequences for the one bumblebee who has to carry an entire colony's future through a winter or a monsoon season, depending on whether you live in Montana or New Mexico or wherever.

It's very important to think about.

And you gotta remember the queen, the bumblebee queen. No one sees.

She's underground,

she's alone,

her metabolism nearly stopped,

potentially flooded and still breathing.

And she's been doing this for millions of years.

You.

Well, I am Kelly Parks, and this has been probably one of my favorite episodes of Secret Pollinators.

And if this episode surprised you as much as it surprised me,

please share it, because most people have no idea there's a bee under their feet right now waiting for spring.

And the links to the Smithsonian article and the original proceedings of the Royal Society B paper are in the show notes. And please be sure to check them out and read both of the articles.

They're really interesting.

Thank you for listening and see you next episode.