AILSA CHANG, HOST:
It's time now for our science news roundup from Short Wave, NPR's science podcast. Reporting this week, we have Rachel Carlson and Regina Barber. Hey to both of you.
REGINA BARBER, BYLINE: Hi.
RACHEL CARLSON, BYLINE: Hi, Ailsa.
CHANG: All right, so you have brought us, as you always do, three science stories that caught your attention this week. What are they?
CARLSON: How some people age extraordinarily well.
BARBER: Endangered eagles feeding on toxic toads without harm.
CHANG: Ooh.
CARLSON: And a new discovery about life in some of the ocean's deepest trenches.
CHANG: Fascinating. But I want to start with the people who age extraordinarily well. I'm very curious if we're talking beyond (inaudible) here.
BARBER: (Laughter).
CHANG: Rachel, kick us off.
CARLSON: For 25 years, Northwestern University has studied these people who are in their 80s but with the memory abilities of someone 50 to 60 years old. They're called SuperAgers. And this week in the journal Alzheimer's & Dementia, researchers summarize some of the secrets SuperAgers seem to have in common.
CHANG: I want to be a SuperAger.
BARBER: Me too. Me too.
CHANG: What's their secret? Tell us.
CARLSON: One commonality between SuperAgers is they all have consistent social interaction, strong social relationships and meaningful interactions with other people.
CHANG: OK, so keep partying. Go ahead.
BARBER: Other factors may include getting good sleep, not just, like, being asleep...
CHANG: Oh.
BARBER: ...For enough time, but getting high-quality sleep. A clinical neuropsychologist at Northwestern University, Dr. Sandra Weintraub, says movement and exercise may also play a key role, but those are more difficult to study objectively.
CHANG: OK. I feel like I'm screwed on sleep.
CARLSON: (Laughter).
CHANG: But I have the social interaction piece down. What about genetics?
CARLSON: I asked another researcher who wasn't involved in the paper, Amanda Maher. She's a clinical neuropsychologist at the University of Michigan, and she told me genetics do play a role in super aging - surprise - but they're not the whole picture. Lots of people have genetic risk factors for Alzheimer's disease or dementia, but don't show any signs of those conditions.
BARBER: So the question is, what helps those people's brains resist those conditions?
CHANG: Yeah, do they have any ideas from this research?
BARBER: Yeah, those two things we already mentioned, like social interaction and sleep, probably play a role. Also, we know that the human brain tends to slow down as we age. Like, even healthy brains shrink, which can make learning and memory harder as people age. But SuperAgers' brains shrink more slowly than brains of their peers, and researchers think that that's involved in avoiding cognitive decline.
CARLSON: SuperAgers also have a lot of this particular type of neuron compared to other people their age. It's called the Von Economo neuron, and it's a big neuron found in humans and some other species like whales and elephants. And researchers think it's related to social relationships or social bonding.
BARBER: And everyone we spoke to said these are all clues to help understand how those behavioral elements and neurological elements are connected to one another. Here's Sandra Weintraub again.
SANDRA WEINTRAUB: Just because you're getting older doesn't mean you're losing it. I think we assume, oh, you know, they're just getting older. They're forgetful. That's not true.
CARLSON: Sandra says there's a lot of variability amongst older people and that SuperAgers offer insight into how we all might be able to keep our brains healthy as we age.
CHANG: Oh, I want that. (Laughter) OK. So we go from SuperAgers to eagles in Japan. They are somehow eating toxic toads and still doing OK. What?
BARBER: Yeah, that's right. So these are eagles which are critically endangered in Japan. A subspecies of these eagles live on two small islands there, and there are only about 200 of them.
CARLSON: And in 1978, cane toads from Central and South America were introduced to one of the islands, Ishigaki. The goal was pest control, to get rid of the bugs eating the cane sugar crops. But the toads are toxic, so predators who fed on them started dying, too.
CHANG: But the eagles are totally fine?
BARBER: Yeah, so a new study documents the fact that they've been feeding on the toads for almost 50 years with no visible symptoms from the cane toads' toxins.
CHANG: Wow.
BARBER: The question is how? Like, I asked Alisa Tobe at Kyoto University about that. She's the lead author of a recent study in the journal BMC Ecology and Evolution. She got blood and tissue samples from these eagles on both islands and compared them to other raptors. And she found that the eagles have a special genetic adaptation to evade these toxins, an adaptation that Alisa says they've had for at least 10,000 years, long before the cane toad showed up on the island.
ALISA TOBE: So by chance, they can feed on them.
CHANG: That's so cool.
BARBER: Yeah.
CHANG: Is there any idea why they even have this adaptation at all?
CARLSON: It turns out it's a somewhat common adaptation. We talked with evolutionary biologist Shabnam Mohammadi about this.
SHABNAM MOHAMMADI: This adaptation isn't unique to the eagles. It's actually very, very widespread. And what we found in rodents, in frogs, in snakes, many predators, sometimes they've gained this adaptation, and they still have it today even though they don't need it.
CHANG: OK, but what's the upshot? Like, is this good news for this endangered species?
CARLSON: Yes and no. So some people have argued we should keep these cane toads for the eagles to feed on since they aren't harmed. But keep in mind, these toads are an invasive species, a human-induced ecological disaster and haven't been good for the environment on Ishigaki. Many animals die of heart attacks if they eat them. So Alisa's still in favor of removing the invasive pest.
BARBER: On the plus side, Shabnam says understanding this adaptation can tell us much more about evolution, like when species so distantly related can have gene sequences that can do the same thing.
CHANG: That's so cool. OK, last topic - life in the deep ocean. Rachel, what's going on down there?
CARLSON: We're talking about the hadal zone, Ailsa. It's the deepest part of the ocean, named for the Greek god of the underworld, Hades. So...
CHANG: Oh, I get it. OK.
BARBER: (Laughter).
CARLSON: Yeah. If you can imagine, based on that name, life is pretty hard down there. No sunlight reaches down this far.
BARBER: And for a long time, researchers thought that life in this zone mostly ate, like, organic matter falling from the ocean surface, like bits of dead animals, like poop.
CHANG: Mm, yum.
BARBER: But now a study in the journal Nature suggests that these deep-sea creatures may also get some energy from chemicals seeping out of the ocean floor.
CHANG: Ooh, how does that work?
BARBER: So I talked to Mengran Du. She's a geochemist at the Chinese Academy of Sciences. And to study all this, she took this incredible journey down nearly 6 miles under the ocean surface in a submersible.
CHANG: Whoa.
BARBER: And she landed in two trenches in the northwest Pacific Ocean near Japan and Russia.
MENGRAN DU: So submersible is like a time machine to me. So whenever I dive to a new ocean somewhere there, it always opened a new world for me.
CARLSON: During her aquatic time travel, she found tubeworms, clams and microbial mats living near cold seeps. Those are places where chemicals like hydrogen sulfide and methane seep out of the ocean floor.
CHANG: Ew, wait.
CARLSON: (Laughter).
CHANG: How do these deep-sea creatures survive on that?
CARLSON: The researchers think that microbes inside of the animals use those chemicals to make organic compounds, then the animals feed off of those compounds.
BARBER: Yeah, and the next step is exploring, like, more trenches at this depth. Now that we know that there's so much life down there, Mengran thinks that there are many more species to discover and more to learn about how life works there.
CHANG: Yeah, but she has to get into a submersible. Not for me.
CARLSON: True.
BARBER: She loved it.
CHANG: (Laughter).
CARLSON: Scary, though.
CHANG: That is Regina Barber and Rachel Carlson from NPR's science podcast, Short Wave, which is doing a whole series on ocean science right now called Sea Camp. Check it out. Thank you to both of you.
BARBER: Thank you.
CARLSON: Thank you.
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