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How do adult strawberry poison frogs pass on toxins to their tadpoles? What happens when scientists add iodine to axolotl tanks? Find out, as our How To Adult hosts Rachel Calderon-Navarro, Project Manager at DFTBA, and Hank Green face off in this episode of SciShow Quiz Show.

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Hosted by: Michael Aranda
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Poison frogs




Hair Dye



 (00:00) to (02:00)


M: Guys, gals, and nonbinary pals, welcome to SciShow Quiz Show, the only quiz show where I didn't think of an intro for this one.  So we're just gonna keep going.  

H: Well, it is the only quiz show where Michael Aranda didn't think of an intro for this one.

M: It's true, it's true.  We'll say this is the only Quiz Show brought to you by the Ryans.  I'm Michael Aranda, your host, and your contestants today are Hank Green, owner of a body size that wears medium t-shirts.

H: Correct.

M: And over here we have Rachel Calderon-Navarro.

R: Yeah.  I also wear a medium.

M: Oh, okay.  

H: I mean, people send me shirts.   They always send me large, and I am tall, but I am not broad.  Put that on a shirt, size medium.  Put it on me.

M: Your Twitter bio says that you wear a medium.

H: And yet, people still send me shirts that are large, including my own mother.

M: Well, today, Hank, you're competing on behalf of Patreon Patron Peter Downing.

H: Hey, Peter.

M: Rachel, you are competing on behalf of Becca Addison.

R: Hi, Becca.

M: Now, you're both gonna start out with 1000 points.  Each time you answer a question correctly, you will win 200 points.  Every time you answer incorrectly, you will lose 100 points.  

H: Oh wow, mixing it up.  I like it.  I like it.  I like these rules.

M: So, whoever has the most points at the end of the game is gonna win some sweet prizes for their Patreon Patron.  Stefan, show our viewers what we're winning today.

S: Oh man, have we got some great prizes for Peter and Becca today.  They're gonna be taking home signed cards from our final round with our contestants' final guesses and wagers on them.  The winner will receive the 'I won SciShow Quiz Show' pin and some secret SciShow swag from, but the loser of today's Quiz Show, will it be Peter?  

 (02:00) to (04:00)

Will it be Becca?  The anticipation is killing me.  They will be receiving the super ultra rare special limited edition 'I lost SciShow Quiz Show' pin.  Wowee, I can't believe it.  Good luck to you, contestants, and back to you, Michael.  

M: Okay, you guys ready?

H: Ready.

M: Round one is all about baby animals.

H: Oh cute.

R: Oh boy.

M: Because they have to be taught how to adult, eh, yeah, eh, eh?

R: Yeah.

M: Okay, so adult strawberry poison frogs secrete a slime with nitrogen containing toxins called alkaloids.  This makes them unappetizing to predators, but these frogs don't make alkaloids inside their bodies.  They get them by eating tiny alkaloid producing mites on the forest floor.  So their tadpoles are pretty helpless when they're born.  They depend on their parents to feed them and somehow pass on this toxic weapon.  So how do they pass it on?  Do they pee on their tadpoles, do they bite their tadpoles with specialized teeth in their upper jaw, do they lay unfertilized eggs for the tadpoles to eat, or do they let their tadpoles eat their puke?

H: I'm gonna say that they lay unfertilized eggs for their tadpoles to eat, 'cause that seems like a callous frog thing to do.  It hasn't changed color yet.

M: You are correct.

H: Yay!  

M: The answer is C, the tadpoles eat unfertilized eggs.  Strawberry poison frogs are in the genus Oophaga, which comes from the Greek for egg-eater and describes the tadpole diet: unfertilized eggs laid by their moms.  Scientists aren't exactly sure what's happening on a cellular level, but they do know that frogs spike these unfertilized eggs with alkaloids.  When strawberry poison frog tadpoles were fed eggs from another species that don't use alkaloids for protection, they didn't have any of these chemicals inside them.  So even though the tadpoles aren't born with these toxins, as soon as they're born, they start storing alkaloids in their bodies just like their parents.

Congratulations, Hank Green, new owner of 200 new points.  

H: Yeah, gonna put those in my points wallet and use them at the points store.  

 (04:00) to (06:00)

M: Okay, now, not every parent can give their baby defensive toxins, but many animals do help their offspring grow until they can forage by themselves.  Mammals, for example, usually provide nutrients in the form of secreted milk, which is full of energy dense fats, proteins, and some sugars.  Caecilians, though, are worm-like leg-less amphibians--

H: People from Sicily?

M: Caecilians.  I--I--  It's C-a-e-c-i-l-i-a-n-s.  

R: This is my ASMR video.

H: Okay.  So it's not people from Sicily?

M: Nahhh.  

H: They might be.

M: These might be from Sicily.  Yes, they might be that.  They don't have mammary glands, but they do make a milk-like secretion to help feed their hatchlings.

H: These are worms?

M: Yes.  Well, they're worm-like leg-less amphibians.

H: Oh, okay, gotcha.

M: Amphibians that look like worms.

H: I interrupted you.  Okay.  

M: So, how do they make their milk-like excretions?  Do they make their skin thicker so their babies can eat chunks of it?

H: Ohhhh, GOD.

M: Do they lay a separate large sac full of nutrients?  Do they stop eating for a few days and puke up a cottage-cheese-like goop, or do they eat a special fat-rich diet and excrete a poop waste?

H: Oh gosh.  There's so many of those things it could be and they're all terrible.

R: Um, cottage cheese.

M: That is incorrect, I'm afraid.

H: It's not cottage cheese.  Well, that's--I feel like I'm one closer now.  I'm gonna say fat poop!  Um...I am also wrong.

M: That is unfortunately incorrect.

H: Aughhh.

M: The correct answer is that they do make their skin thicker so that babies can eat chunks of it.


M: The answer is A, they thicken their skin so their babies can eat it.  Some Caecilians give birth to live young, which use specialized scraping teeth to feed on the lining of their mom's oviduct before they're born, but some egg-laying species still hatch offspring that have these scraping teeth and these mothers modify their skin and bulk it up with fats and proteins so their babies get a delicious meal by peeling it off and eating it.

 (06:00) to (08:00)

Caecilians do survive this maternal dermatotrophy, as it's called, but at a cost.  One study measured that after one week of skin-eating, the moms lost about 14% of their body weight, so it's definitely a self-sacrifice, but researchers think that this strategy could be an evolutionary transition between laying eggs and producing more self-sufficient live-born young.

H: Oh, that's awful.  Oh my God.  I love...I love animals.  I love life.  Biology is so weird.

R: I feel like I just got very pale all of a sudden.

H: Rachel has to go lay down.

M: We can fix that in post.  Alright, question three.  Aoxlotls, also known as Mexican salamanders, are unique little aquatic amphibians.  They become adults and have offspring without going through metamorphosis.  They're basically stuck in their awkward teenage years with chubbier bodies and external gill stocks like other salamander larvae.  This child-like appearance is called neoteny.  Now, iodine is an element used by many animals to make thyroid hormones, which can help regulate things from heart rate to metabolism, and when scientists add iodine to an axolotl tank, a weird physical change can happen.  Does the axolotl reabsorb its external gills and grow lungs?  Does it turn black and white?  Does it reabsorb its tail?  Does it grow longer fang-like teeth?

R: It uh, reabsorbs its gills and grows lungs.

H: That's what I was gonna say.

M: You are correct.  

The answer is A, reabsorb its external gills and grow lungs.  Different species of salamanders have shown neoteny when isolated in lakes or reservoirs, which makes researchers think it's a survival strategy when there's not enough food or balanced nutrients.  Axolotls seem to be completely neotenic though.

 (08:00) to (10:00)

Even when they have plenty of food and nutrients, they don't produce enough of the thyroid stimulating hormone that kickstarts metamorphosis in other salamanders.  So when scientists add iodine to an axolotl tank, their thryroid glands seem to be kicked into high gear and produce hormones to transform their bodies from aquatic creatures to land animals.  They lose their gill stocks, grow lungs, get slimmer with sturdier legs, and end up looking kind of like a North American tiger salamander.  

All:  Haha!  Aha!  Ahahahah!

H: You snuck in there.

R: Points! 

H: I think we're tied now.

R: Yeah.  We lost and gained points.

M: Alright, our next round of questions is all about chemical dyes.  People have been coloring fabrics with natural dyes from plants and minerals for centuries, but once we got started better understanding chemistry, we started to make synthetic dyes.  The first documented synthetic dye was called (?~8:52).  It's a bright purple color and it was made by accident by the scientist William Henry Perkin in 1856.  He was trying to synthesize a different chemical since it was only extracted from one genus of tree bark at the time and there was a pretty high demand for the stuff.  What was the chemical?  Was it morphine, a strong pain reliever?  Quinine, a medication used to treat malaria?  Caffeine, or cyclosporine, a medication that suppresses the immune system?

R: Uhh.  Uhh.  

H: I was really expecting a certain thing that you didn't say.  So.  

R: Um.

H: I guess I'll just hit the thing, but I don't remember any of the things, 'cause I was certain that I knew the answer that clearly is not correct.  I thought it was gonna be aspirin.  But what is it?  

M: You tell me.

H: Oh, no, no, don't, I didn't say that.  What's the...

M: Your options are morphine, quinine, caffeine, cyclosporine.

H: I'm gonna go with quinine. 

M: You are correct.

H: Okay.  Cool.  Hooray.

M: Congratulations.

The answer is B, quinine.  Perkin was trying to synthesize quinine, the main anti-malerial drug at the time.  

 (10:00) to (12:00)

We think quinine messes with how the malaria parasite interacts with hemoglobin, the main proteins in our red blood cells.  He started with aniline, which is an organic compound that was often extracted from coal tar.  After some chemical reactions, he ended up with a vivid purple dye that he called (?~10:14) instead of quinine.   It was the first of many synthetic aniline dyes and chemists started experimenting to produce all sorts of colors, but aniline is pretty toxic and people who wore clothing that was colored with these dyes sometimes had health problems, so we started phasing them out for safer alternatives.

H: It seemed like the kind of thing that would be in a tree bark.  

M: Yeah.

H: Bitter.

M: Now, humans also like changing hair color with dyes.  You can use things like bleach, also known as sodium hypochloride, to break some chemical bonds and break up the melanin pigment in your hairs so that it lightens the color and then you can add different chemical pigments that bind to the proteins in your hair cortex to give you a new look.  Around the 16th and 17th century, fashionable ladies sometimes used what was called 'oil of vitriol' to lighten dark hair to be a more reddish brown, but it also wasn't the best thing health-wise and could make your hair fall out or irritate your skin.  What was oil of vitriol?

H: It's--I don't know, it's a great name, though.  Oil of vitriol.  Oh, it's good.  It's like you just got real mad at somebody and then collected it.  Just like, here's my anger, I've scraped it off with a squeegee and put it into this bottle, now put it in your hair, Victorian woman.  

R: 'Cause you'll lose it.  

M: Was it hydrogen peroxide, fermented leeches, beechwood ash mixed with goat fat, or sulfuric acid?

H: Ow.

R: Ahh ow.  Sorry.  You have a really hard finger.

H: Uh, thank you?  I've been working on it.

R: But you were first.  

H: I was gonna say hydrogen peroxide.

M: That is incorrect, I'm afraid.  

H: It's not an oil!  It's not even close to an oil!  

 (12:00) to (14:00)

What was I thinking?

M: I don't know.  

R: Um, what was the last one?  

M: Well, your options are now fermented leeches, beechwood ash mixed with goat fat, or sulfuric acid.

R: Um, sulfuric acid.

M: That is correct.

H: Oh!  That's not an oil either.  

M: Hmm, no, but it is the oil of vitriol (evil laugh)

The answer is D, sulfuric acid.  All of these things have been used as hair dye at some point in history.  Hydrogen peroxide is a modern-day lightener, the Romans used fermented leeches to dye their hair black, and Germanic peoples used ash and goat fats to create a red color, and oil of vitriol is what old timey chemists called sulfuric acid.  It probably worked like bleach, by damaging the hair follicles and the melanin pigment inside, but sulfuric acid is also incredibly corrosive so it probably was damaging peoples' hair a bit too much, causing it to fall out and would damage any skin it happened to touch.

And with that, it's time for our final round.  Okay, Rachel, you've got 1300 points.  Hank, you've got 1200 points.  You're gonna bet any number of those points on your answer to the next question, which is about bacteria.  While you place your bets, we'll be right back after this maybe-commercial break.

Welcome back.  You guys have placed your bets.  You ready for the question?

H: Yes sir.

M: Okay.  Not only are bacteria everywhere, but we humans use them for a lot of different things, from making butter to producing antibiotics and researchers are still discovering new ways to make these microbes useful, like, in February of this year, a team of researchers built a synthetic iron-containing molecule that they called DSFO+ and stuck it into a bacterial cell membrane to give that bacteria a brand new superpower.  What can these bacteria do?  Can they act as synthetic red blood cells, generate an electric current, reinforce steel so that it doesn't wear down as much over time, or act as tiny incredibly strong magnets?

 (14:00) to (16:00)

H: Interesting.  Any of those is very cool, so hats off to those scientists.  I'm gonna make my guess right now.  I forgot all of the answers.

R: I did as well.

M: Act as synthetic red blood cells, generate an electric current, reinforce steel so that it doesn't wear down as much over time, or act as tiny, incredibly strong magnets?

H: I can't write.

M: Do you have your answer, Rachel?  

R: Yes.

M: Alright.  Display your answers.  Hank is correct.

H: Yaaay!

M: The answer is B, generate an electric current.  This team of researchers was inspired by electrogenic bacteria in nature that live in places without oxygen.  They use proteins in their cell membranes called PPV-COEs to move electrons and help them make energy, so the scientists wanted to make a molecule that could give this superpower to any bacteria, because having teeny tiny power generators could be really useful.  To do that, they created DSFO+, a synthetic molecule that mimics the thickness and basic structure of the molecules in cell membranes, but it also has an extra iron atom in the middle to help shuttle electrons back and forth.  The researchers say it's kind of like a prosthetic limb, because it's not chemically a protein, but it's acting like one in the cell membrane.  Now, these engineered bacteria probably aren't going to be powering entire homes or cities, but the researchers hope they could help with smaller scale sustainable energy like making enough power for a wastewater treatment plant.

I think that means Hank is our winner for this episode of SciShow Quiz Show.

H: I definitely won.

M: Thank you, ladies and gentlemen, for hanging out.  If you wanna see more of Rachel and Hank together, you can go to  A big thank you to this episode's writer and editor, Ceri Riley and Alyssa Lerner respectively.  If you want to help us make more videos like this, you can go to and of course, don't forget to go to and subscribe.

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