The real reason why mosquitoes buzz | DIY Neuroscience, a TED series

229,894 views ・ 2018-09-15

TED


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Translator: Joseph Geni Reviewer: Krystian Aparta
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(Mosquito buzzing)
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Greg Gage: We've all heard the annoying sound of a mosquito,
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and we will stop at nothing to make it go away.
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While this sound may be maddening to us,
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perhaps it's music to a mosquito's ears.
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The mosquito's nervous system has almost as many sensory auditory cells as we do.
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But why would they have so many in such a small body,
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and why would they need to be so sensitive to sounds?
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The answer is love.
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[DIY Neuroscience]
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(Music)
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As humans, we do a lot to attract each other.
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Some things are conscious --
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we put on makeup and make sure we smell nice.
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And some are unconscious.
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You may unconsciously point your body or even sit closer to someone you like.
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These are courtship behaviors, and a lot of animals have them.
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And mosquitoes are no different.
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So Haley's been spending her summer bravely listening to mosquitoes,
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and what she observed may surprise you.
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So we want to investigate how the mosquitoes make their song.
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So Haley, how do we record their wing beats?
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Haley Smith: We need to tether them.
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First, we anesthetize them in a fridge or a bed of ice.
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And then I transfer them to this petri dish of ice,
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just to get them even more anesthetized.
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Next, I take an insect pin,
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and what I do is put a tiny little dab of superglue on this pin.
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I want to make sure that I get it on his thorax above his wings
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so that when he is suspended, his wings are still free to move.
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So here's one down.
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It's really hard to catch male mosquitoes in the wild
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because females are the only mosquitoes that are attracted to humans.
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They feed on human blood.
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And now, we can try to get some recordings from them.
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So this is the stand that I use to hold them.
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I like to place it right over the microphone
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so that I can get a recording of the buzzing that you hear.
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That sound is generated by how fast they're beating their wings.
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This is a male.
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The males have very bushy antennae, and they look kind of feathery.
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And they are also much smaller.
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GG: So he's flying at around 600 hertz.
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Can we try a female mosquito?
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HS: Sure, here we go.
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(Mosquito buzzing, lower pitch)
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GG: Wow.
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HS: This is a much lower frequency than the male.
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GG: Yeah, it sounds completely different.
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(Mosquito buzzing)
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(Mosquito buzzing, lower pitch)
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So is it because they're two different mosquitoes,
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or because they're male and female?
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HS: It's because they're male and female.
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GG: Alright, let's verify that.
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Can you bring in another female and see if she sounds
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like mosquito A or mosquito B?
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HS: Yeah.
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(Mosquito buzzing, lower pitch)
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And again, she is much lower than the male.
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GG: Yeah, she sounds different.
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(Mosquito buzzing, lower pitch)
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Yeah, she's spot-on 400.
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HS: She really is. GG: That's really bizarre.
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HS: The females are at a much lower pitch. They were around 400 hertz.
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HS: And all of the females were around that, too.
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They were much larger than the males,
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so they didn't have to flap their wings as fast to stay in free flight.
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GG: So they have larger wings, so they're flapping slower.
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And you noticed that all the females have the same frequency, roughly?
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And the males do, too. That's kind of interesting.
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So that must mean something.
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Well, let's see what happens when we put the male and the female together.
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(Mosquitoes buzzing; pitch varies)
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HS: When I put them into the same hearing range,
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I noticed that they were kind of changing their tones.
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It was kind of more dull, almost.
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(Mosquitoes buzzing)
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And when I put it back in my spectrogram to see their interaction,
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they were meeting at the same tone.
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GG: OK, pause.
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The males and females are singing a duet,
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meaning that they adjust their wings to be able to produce a common tone.
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You have the male singing up here at G,
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and you have the female singing down here at D,
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and when they get together,
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you're saying that they change the frequency of their wings
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such that they come together?
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HS: Yeah, exactly. GG: And they sort of sing a duet.
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(Mosquitoes gradually adjusting to identical pitch)
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HS: They're communicating to let each other know
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that they've basically found a potential mate.
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GG: So in other words,
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the female tends to choose a male that best sings her duet.
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And studies have found that if she's pregnant,
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she doesn't even bother.
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So if we can understand the mosquito mating behavior,
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we may be able to disrupt it in the wild and prevent diseases like malaria.
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But for now, the next time you hear a mosquito buzzing,
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just pause and remember she may be in love
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and she may be singing her song,
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looking for her perfect match.
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(Mosquito buzzing)
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(Smack)
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