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  • Thanks to Brilliant for supporting this episode of SciShow.

  • Go to Brilliant.org/SciShow to learn how you can take your STEM skills to the next level

  • this year.

  • {♫Intro♫}

  • We're not going to sit here and pretend that platypuses aren't weird.

  • They're mammals but they have a duck face and they lay eggs and they also have venom.

  • Of all the weird animals that exist in the world, they're up there with the weirdest.

  • And by the way... they're also fluorescent.

  • That thick, waterproof fur that reassures us that platypuses are, in fact, mammals also

  • glows in the dark.

  • Before you dismiss all of platypus-kind as just trying to mess with our understanding

  • of reality, though, the fact is this ability isn't all that weird -- and might be way

  • more common than we realize.

  • Fluorescence refers to the ability of a material to absorb light and then re-emit it in another

  • color.

  • This is different from bioluminescence, which is when an animal can produce light through

  • a chemical reaction.

  • And actuallylots of animals are fluorescent.

  • Scorpions have fluorescent bodies, for example, and puffins have fluorescent markings on their

  • beaks.

  • But up until recently, there weren't too many mammals known to fluorescemostly

  • just opossums and their close marsupial relatives.

  • Then New World flying squirrels, which are placental mammals, were found to have a similar

  • talentthey fluoresce pink.

  • And in a 2020 study, researchers shone a UV flashlight at a couple of preserved platypus

  • specimens in a museum -- and found them to glow a lovely shade of cyan.

  • Scientists aren't yet sure why any animals, including mammals, would want to fluoresce.

  • So far, all the fluorescent mammals we've discovered are either nocturnal or crepuscular

  • -- meaning active during sunrise and sunset.

  • The diurnal, or daytime-active, species we've examined don't fluoresce -- meaning we day

  • dwellers lost out on looking awesome at raves.

  • Crepuscular animals, like the flying squirrels, are active when UV light is more intense but

  • visibility is otherwise poor, so the ability to absorb UV and emit it as visible light

  • might help them see each other.

  • For platypuses, we think fluorescence might help them hide.

  • Some of their predators use UV light to see, and fur that absorbs UV light might be harder

  • to spot.

  • But here's the thing: we can all agree that platypuses are mammalian oddballs, but fluorescence

  • might not really be that weird.

  • It's actually even possible it's common.

  • Most of us don't go around shining black lights at raccoons or coyotes or whatever,

  • so there could be a bunch of fluorescent mammals right under our noses.

  • And we've got reason to think fluorescence could be widespread.

  • Flying squirrels are placental mammals.

  • Opossums are marsupials.

  • And platypuses are monotremes.

  • That's all three major groups of mammals.

  • In evolutionary biology, when all the members of a group have a trait, we usually infer

  • they inherited it from their common ancestor.

  • That means mammalian fluorescence could be an ancestral trait.

  • Though these animals could also have evolved it separately, as an example of convergent

  • evolution.

  • More research is needed, but we should be able to figure this out by looking at whatever

  • genetic mechanism makes these mammals glow.

  • If it's the same in all mammals, that hints at it being ancestral.

  • Convergent evolution tends to co-opt different genes to do similar jobs.

  • But it might make sense for all mammals to have been fluorescent back in the day.

  • You see, early mammals were nocturnal by necessitykeeping to the shadows to avoid becoming

  • dinosaur chow.

  • And fluorescence could have given those early night dwellers advantages just as it does

  • now.

  • So platypuses may have a lot of weird qualities, but the whole glow in the dark thing probably

  • isn't one of them.

  • And that in itself is pretty weird.

  • Fluorescence is just one place where biology meets physics.

  • And if you want to know more about how these platypuses come by their bizarre glow, you

  • might enjoy Brilliant's course Waves and Light.

  • It'll teach what waves are and how they travel, from glowing critters to earthquakes.

  • And if you want to learn even more, you're in luck, because Brilliant has loads of courses

  • designed by leading educators and lifelong learners, to help you understand the world

  • around you.

  • The first 200 people to sign up at Brilliant.org/SciShow will get 20% off an annual premium subscription

  • to Brilliant.

  • So if you'd like to start off your year right, head on over and see if Brilliant is

  • right for you.

  • {♫Outro♫}

Thanks to Brilliant for supporting this episode of SciShow.

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B2 中高級 美國腔

所以显然鸭嘴兽在黑暗中发光(So Apparently Platypuses Glow in the Dark)

  • 19 1
    joey joey 發佈於 2021 年 07 月 01 日
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