This week in science: moths' anti-bat signal, fish who count and GMO crops at home

ARI SHAPIRO, HOST:

It's time now for our regular science news roundup with our friends at NPR's Short Wave podcast. And this week we've got Regina Barber and Margaret Cirino. Hey there.

REGINA BARBER, BYLINE: Hey.

MARGARET CIRINO, BYLINE: Hey, guys.

SHAPIRO: Well, how this works is you've brought us three science stories that caught your attention this week. What's on the menu this week?

CIRINO: How about moths with an anti-bat signal built into their wings?

SHAPIRO: Oh.

CIRINO: Yeah.

BARBER: And clownfish that could possibly count up to three.

CIRINO: Plus tomatoes that are purple and potentially better for you.

SHAPIRO: Sounds delicious. Let's start with the moths. Not long ago, we learned the science behind why they are attracted to flame. Now you're telling us they can also repel bats?

BARBER: Yeah. So these moths don't want to be eaten by bats, so they make this clicking sound with their wings that can disrupt the bats' echolocation.

CIRINO: Yeah, so the real sound is out of human hearing range, but if it's slowed down enough, it sounds like...

(SOUNDBITE OF MOTH WING CLICKING)

SHAPIRO: Yeah. If I were a bat, I'd stay away from that.

CIRINO: Yeah.

BARBER: (Laughter) Yeah, it's wild. They evolved to make the sound with their wings every time they fly as a way to compensate for being deaf because they can't hear when predators like bats are around.

CIRINO: And this warning system, we've actually known about it for a while now. But exactly how they make these sounds was the mystery until this week. A new study in the journal Proceedings of the National Academy of Sciences details how these ermine moths are able to do this with their wings.

SHAPIRO: And what's the answer to the question?

BARBER: So I talked to a researcher on this study, Marc Holderied, and he mentioned that the wings that he and his team collected, like, in Bristol, U.K., actually buckle and unbuckle.

SHAPIRO: Huh.

CIRINO: Yeah, Ari, think of a plastic bottle that deforms and makes a little click-click, and then deforms back. It makes another click.

SHAPIRO: Yeah.

CIRINO: That's what's happening here, but much more elegantly. A part of the moth's hind wings buckle and then unbuckle sequentially along the ridges there. And it's completely reversible and happening hundreds, thousands of times in flight without damaging the wing.

SHAPIRO: Wow. Is that unique to this kind of moth?

BARBER: No, actually it's not. But Marc says that they haven't seen this particular mechanism before.

MARC HOLDERIED: But it's a sound production mechanism that's completely novel. It doesn't require any muscles. Just the physics and the mechanics of the sound production is baffling.

BARBER: But now that they know what it is, they're seeing it in other insects.

CIRINO: And one last thing to say about this, nature is showing scientists how this kind of buckling process can be beneficial, which is the opposite of how it's viewed in engineering. You know, in engineering, buckling is generally associated with failures and damaged building material. So maybe engineers can take note.

SHAPIRO: Cool. All right, let's pivot to the second story. Take us underwater into new research about clownfish. They can count?

CIRINO: Well, maybe - a team at Okinawa Institute of Science and Technology is saying clown anemone fish - that's what Nemo is - could be counting the numbers of white stripes on each other.

SHAPIRO: But why would they want to do that?

BARBER: Yeah, well, so you need to know two things about these fish, Ari. First, adult clown anemone fish have three stripes. And second, they're much more aggressive and territorial than the fish in "Finding Nemo."

SHAPIRO: Oh, so I'm not going to watch the movie the same way again after this, is what you're telling me?

BARBER: Yes, absolutely.

CIRINO: And here's the thing, clown anemone fish are most aggressive toward their own species 'cause they want to protect their cute anemone kingdom from being taken over from within. Sorry to burst your bubble, Ari.

SHAPIRO: No, actually, I kind of like the idea of these really cute fish actually being total jerks to each other in real life.

CIRINO: Right. Vincent Laudet, a researcher on the study, told me that the alpha female seems to be most aggressive toward other anemone fish also with three stripes 'cause they look most like herself.

BARBER: (Laughter).

CIRINO: So the scientists think the fish are counting.

SHAPIRO: We love a diva.

CIRINO: (Laughter).

SHAPIRO: So how did they find out that the fish are counting stripes?

BARBER: Right. So researchers did these two experiments, led by Kina Hayashi. And first they placed different species of anemone fish with different numbers of white stripes inside the tank and observe how often and for how long the clownfish would behave aggressively by either circling or charging towards the others.

CIRINO: And then in the second set, the researchers painted little plastic, like, orange disks with zero, one, two or three stripes, and again measured aggressive behaviors. And the more stripes on the fish or the disk, the more they were circled or charged.

SHAPIRO: Wow. So the fish are actually counting stripes.

CIRINO: Yeah. I mean, I will note, one expert I talked to, Karen Carleton - a biologist not affiliated with this study - she was a bit skeptical. She pointed out to me that this might just as well be clown anemone fish picking up on other visual cues, you know, different coloration on the fins across species, for example.

BARBER: Right. And so, as it often is the case in science, more experiments need to be done to know for sure if the fish are actually counting stripes. But Vincent says either way, we need to give these fish more credit.

VINCENT LAUDET: People think fish are dumb because fish have no facial expression that we can read. But in fact, fish are extremely clever. Individuals have their own personality. And we see that very clearly with anemone fish.

SHAPIRO: Honestly, I could listen to a weekly segment from that man. But let's pivot to the third scientific discovery you have brought us, just in time for seedlings sprouting in the greenhouse as we approach spring. So what have you learned about purple tomatoes?

BARBER: Right. So the color is kind of like a Concord grape. And last year, the Food and Drug Administration gave the go ahead for some small farmers to grow and sell this purple tomato. But now gardeners can buy the seeds to grow them at home.

CIRINO: Yeah, they just went on sale this past weekend. And this is the first time transgenic seeds - so they contain genetic material from two different organisms - have been sold directly to customers in the U.S. Sasa Woodruff with Boise State Public Radio wrote about it for NPR.

SHAPIRO: OK, not to brag, but I grow a lot of different colored tomatoes in my garden. What makes this one so special?

CIRINO: I mean, love that. But there's a reason behind the purple. Norfolk Plant Sciences, the company that created this tomato, hacked the color genes from a snapdragon flower into the plant. But those genes not only give the tomato its purple color, they boost its levels of anthocyanin.

BARBER: So anthocyanins are antioxidants, and these compounds have been shown to have anti-cancer and anti-inflammatory effects. So think blueberries, blackberries, eggplants - they mostly get their color from anthocyanins.

SHAPIRO: I love a purple fruit. And yes, eggplants and tomatoes are fruits.

BARBER: You're right. You tell them, Ari.

SHAPIRO: Thank you. OK, so these purple tomatoes are genetically modified. And look, GMOs have had a perception problem in the U.S., right?

CIRINO: Very true - a 2020 Pew Research study showed that most Americans see GMOs as worse for their health than foods with no genetic modification. But since GMOs were introduced three decades ago, studies don't actually show any harm. And the FDA has concluded that there isn't a health risk to eating genetically modified foods currently on the market.

BARBER: And some of this negative perception can be traced back to the first wave of genetically modified crops that were developed to be resistant to herbicides.

SHAPIRO: Yeah, it brings to mind, like, agribusiness and huge corporations that are kind of biohacking crops, right?

CIRINO: Right. Yeah, it was all about making crops easier to grow. But the purple tomato could be considered part of a new wave in GMO foods with the goal to increase nutritional value. So the GMO industry is hoping the purple tomato could help change the conversation.

SHAPIRO: I want an orange tomato with three white stripes like a clownfish.

BARBER: (Laughter).

CIRINO: Yeah. Cannot wait (laughter).

BARBER: Make the clownfish angry.

SHAPIRO: That's Regina Barber and Margaret Cirino from NPR's science podcast, Short Wave, where you can learn about new discoveries, everyday mysteries and the science behind the headlines. Always great having you here.

BARBER: Thank you, Ari.

CIRINO: Thanks, Ari.

(SOUNDBITE OF GLASS ANIMALS SONG, "TANGERINE") Transcript provided by NPR, Copyright NPR.