4 Animals That Don’t Have Resident Gut Microbiomes

We humans couldn’t live without our gut microbes, but not all animals rely on microscopic digestive communities like we do. And understanding why these animals ditched their microbial partners can teach us a lot about the costs and benefits of making evolutionary friends.
Hosted by: Michael Aranda
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Sources:
fiererlab.org/wp-content/uploa...
www2.rowland.harvard.edu/file...
www.kavlifoundation.org/about...
Bats:
academic.oup.com/femsle/artic...
msystems.asm.org/content/4/6/...
www.nwf.org/Educational-Resou...
rcin.org.pl/Content/12254/BI00...
www.asm.org/Press-Releases/20...
Caterpillars:
www.pnas.org/content/early/20...
Ants:
academic.oup.com/icb/article/...
www.ncbi.nlm.nih.gov/pubmed/2...
www.pnas.org/content/112/33/1...
www.researchgate.net/publicat...
Stick bugs:
www.nature.com/articles/srep2...
bmcgenomics.biomedcentral.com...
www.sciencedirect.com/science...
www.sciencedirect.com/science...
www.sciencedirect.com/science...
www.ncbi.nlm.nih.gov/pmc/arti...
bioone.org/journals/Journal-o...
www.ncbi.nlm.nih.gov/pmc/arti...
www.the-scientist.com/news-op...
Oysters:
aem.asm.org/content/aem/44/5/...
link.springer.com/article/10....
link.springer.com/article/10....
www.frontiersin.org/articles/...
Images:
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
www.flickr.com/photos/sanmart...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...

[@2MeterLP]

My guess on caterpillars: many gut bacteria can be incredibly harmful when they get anywhere other than the gut. And Caterpillars completely turn into goo before turning into butterflies, so having lots of bacteria may hurt them during that stage.

[@patrickmccurry1563]

Interesting idea, but that wouldn't explain why so few other metamorphosizing insects lack gut bacteria.

[@lizziebanyan8468]

Yes, a caterpillar is basically in an embryonic stage?

[@MrAlRats]

Is that your gut feeling?

[@erichodge567]

Nice hypothesis.

[@nathanlevesque7812]

not completely

[@tylerknight99]

I like this guy. His timbre, gestures and intonation are all very pleasant and engaging to listen to.

[@dolomedestenebrosus9564]

I love Michael's delivery. He might be my favourite host. Hi Michael!

[@JosiahMcCarthy]

He is my favorite host

[@sebastianelytron8450]

Why are bacteria bad at math? Because they multiply by dividing.

[@dakotasimms7270]

ha

[@Devadas44]

Great! thats for the laugh

[@averyjenson]

Oh that’s a great one. I’ll be telling that to my students one day.

[@user-ed9qu5im2y]

@@myutubechannel_nr1 So actually, bacteria are good at math.

[@smurfyday]

@@averyjenson Don't. That makes sense to people not good at math. Multiplication and divisions are the same. Multiplying by 1/3 is the same as dividing by 3, and vice versa.

[@collinbarker]

Caterpillars not having bacteria does make some sense. Probably not good having a pile of hungry bacteria inside a cocoon with you, when you are a literal pile of goo being put back together into a butterfly.

[@Tinyvalkyrie410]

That would make sense except for the fact that caterpillars are the exception not the rule. Most insects that go through metamorphosis do have gut bacteria. Some have gut bacteria strong enough to digest plastic. If it was a risk specifically due to metamorphosis, you would expect the lack of gut bacteria to be very common in animals that use that strategy.

[@nathanlevesque7812]

@@AxxLAfriku shoosh

[@BTheBlindRef]

the "pile of goo" idea of metamorphosis is a myth anyway (or at least highly exaggerated). The insects retain structure and most of the adult parts have already started to form under their final external shed layer when they form their chrysalises.

[@MarcMTG]

@@BTheBlindRef Correct. Wings have already started develloping inside the caterpillar transformed into a chrysalis

[@ArchFundy]

Query: Do flightless birds have a more robust microbiome?

[@Boogers32150]

Canuck Fundy - yea I’d love to see if ostriches or penguins have a consistent gut flora.

[@kylestanley7843]

VERY good question!

[@KnightRaymund]

Oh, nice question

[@jaschabull2365]

Mind you, if their ancestors could fly, maybe they lost their robust microbiome earlier and never got it back.

[@thylacocoalthy6228]

It's been studied in Ostriches and looks to be the case, considering they're capable of cellulose digestion and apparently structurally have a fermenting hind gut, with fiber digesting bacteria found in their ceca in 2010.

[@TragoudistrosMPH]

I've never heard of horizontal gene transfer in eukaryotes! I've never heard of animals without gut microbiomes.. This episode was amazing!

[@royalbloodedledgend]

7:34 “horizontal gene transfer” Sounds very, very dirty

[@xenorac]

I really thought it was a term for... Well, you know.

[@matty9460]

@Him unless you have an std, vertical gene transfer is all you'll be doing

[@mechasentai]

I "love" all the people saying we need to get rid of all bats. I'm like yeah let's just bring on the full on unabashed apocalypse.

[@grannykiminalaska]

Ya, I'll keep all the mosquitoe eating bats we have in Alaska.

[@Sorcerers_Apprentice]

Just stop eating them and wrecking their habitat. We need them to eat insects and pollinate plants.

[@carissstewart3211]

Seems much easier just to leave bats alone. They belong in the wild, not crowded markets.

[@BigMobe]

Bats are whatever, we need to focus on eliminating all species of mosquitoes that bite humans from the face of the Earth.

[@patrickmccurry1563]

@@carissstewart3211 Major problem with that is that humans keep changing what is, and sadly was, the wild.

[@Zen-rl5pv]

Really enjoyed the bit at the end where you mentioned that assumptions in microbiomes (and by proxy science) shouldn't be made conclusively and that retesting a finding can't hurt because future findings can contradict earlier ones with the use or more modern methodologies and better instruments, a great reminder to stay curious!

[@user-zw5jj2uf1p]

What I love about this topic is that by now we're so normalized to the idea of our gut biome, an idea that I was completely unaware of just 5 years ago and that sounded so mind-boggling at the time, but that now we're surprised that some animals DON'T have it

[@threeMetreJim]

Humans: *We have gut bacteria* Bats: *We Have Viruses*

[@adamingi]

Take it or leave it

[@cookeymonster83]

We have both

[@paulg3336]

Humans: "We over populate then destroy and encroach on wildlife's habitats and then blame the wildlife for the consequences." Bats: Gaia: "I'll take this one ,my children - yes ,Humanity, I was meaning to discuss this with you. As I am a very busy woman , I will send my hordes of adaptable pathogens to have a word."

[@sdfkjgh]

8:12 I wonder how much research has been done on these endogenous stick insect antibiotics. Could they be useful in combating drug-resistant diseases?

[@midnight8341]

Depends on what type of antibiotics they produce. Most antibiotics have cross-resistances with some others of their group, so real multiresistant bacteria might be resistant against some of them as well. Multiresistant bacteria don't do very good in the environment, because they waste a lot of energy for useless defences there, because there are very little of our antibiotics in the environment. So, there they don't have an evolutionary advantage. Also, there's always the problem that even if an antibiotic works well against multiresistant bacteria, it shouldn't kill the person around it.

[@whoa.slowdownthere4633]

@@midnight8341 I always learn more on KZbin than school.

[@midnight8341]

@@whoa.slowdownthere4633 that's... pretty sad, actually ^^"

[@ayame316]

Wow stick insects are even more awesome than I thought! We really need to take care of these species.

[@danielm.1441]

To the tune of Teenage Mutant Ninja/Hero Turtles: Super Basic Caterpillars...

[@MinhNguyen-ue5ct]

Wouldn't caterpillars need as sterile a digestive system as they can get for when they metamorphose? Someone make an experiment with caterpillars who have a microbiome introduced to their guts before they pupate!

[@VincentGonzalezVeg]

follow me on instagram and reddit and twitter @TheLivingVoid i have some gulf fratillary caterpillar's outdoors in the passiflora careula and id be up for putting them in a terrarium and feeding them food gel or however they could get the bacteria in their gut the best, and sample their waste and look at it under a slide and grow cultures to look at more discrete species in the waste stay a strong swarm!

[@OlleLindestad]

This would be a tricky experiment to do, because the last thing a caterpillar does before pupating is to have a great big cleansing poo (the technical term is a "gut purge"). I think it's actually quite likely that having a sterile gut is valuable during metamorphosis, but yeah, it'd be difficult to test.

[@franzy871]

Wow! I didn't know bats have such an interesting digestive system! Awesome work!

[@christelheadington1136]

Imagine if people pooped as often as bats, the great toilet paper grabs would be even more insane.

[@emperortbw402]

Yep, they have all sorts of interesting features, and most of them incidentally make them the perfect breeding ground for super diseases like the CCP Virus, Ebola, Marburg, and many others.

[@Sciencerely]

I think gut microbiome research is awesome! Right now, There is a cool trend in human biology to study the impact of the gut microbiome on our health. We are finding more and more evidence that certain compositions of bacteria in our gut might influence our mood. Some bacteria seem to be able to activate neural pathways and central nervous system signaling systems which contribute towards anxiety disorders and depression. Bacteria in our mouth might even contribute towards Alzheimer's disease (I made a video about this a while ago, there is much going on!). It's intriguing how much we can still learn about ourselves!

[@siyacer]

@@-_.-._- lactobacillus in yogurt

[@SovereignwindVODs]

pretty sure the guys here at scishow already made an episode touching on that several months ago.

[@johnopalko5223]

My weird brain just imagined a broadcast from bat air traffic control: "Attention all bats: Fecal dumping in progress 1/16 mile, bearing 268 degrees, from the big tree on the corner of Fourth and Main at 150 feet." (I think this whole quarantine thing is making me punchy.)

[@scottmantooth8785]

*nothing weird about that brain of yours...the voices in my own approve of your post*

[@keirfarnum6811]

John Opalko You’re totally allowed. Made me chuckle.

[@MrPepelongstockings]

Michael is one of the better scischow hosts... not that anybody could beat Hank for lovability. He's just got a better pacing and tenor to his voice, very classically presenter-like.

[@Bloodreign137]

“Microbial crouton” was my nickname in high school.. it was a tough time

[@xetrius3671]

1:36 reaction: "their poops turned pink..." I would predict that the dye would form a solution with the digestive fluids and travel faster then the solid matter. Up to the point where the liquids are extracted. Colouring the solid matter that was already in its digestive system prior to eating the coloured food. Without the need for lightning fast digestion and high efficiency absorption of nutrients.

[@dglukesluthier]

This is utterly fascinating, thank you

[@amey409]

Loved the video ! Wonderful

[@Varizen87]

"Dropping loads more often" Ba-Dum-TIS! Mr. Aranda... Ba-Dum-Tis!...

[@Raithe11]

I can't believe I'm housing embezzlers in my intestines.

[@rusdanibudiwicaksono1879]

No, they are peasants and paying you your body tax in nutrient and vitamins.

[@jamesburleson1916]

You're under arrest for aiding and abetting. Make sure you actually rest and not just watch youtube all night.

[@arthas640]

@@jamesburleson1916 *drinks an entire case of Red Bull* You'll never take me alive, copper!

[@ishawiechers]

Bruh this is by far my best yt channel to watch while high

[@LEDewey_MD]

Fascinating episode!

[@OorahhColeman]

I'm convinced there are bots that dislike every SciShow video.

[@Axodus]

If the ratio is small like this one it's usually accidental.

[@arthas640]

@@Axodus thats how i think it is for alot of videos. I'd say around 5-10% of the time I vote on a video its an accidental dislike from my phone bouncing around in my pocket (I listen to youtube alot while working or walking my dogs). I probably do more accidental votes than that but I only catch them when I rewatch a video and see a dislike on a video I dont hate. It stands to reason that alot of dislikes on videos like this are accidental rather than malicious.

[@cookeymonster83]

Probably Creationists. Or Muslims.

[@xXxCobraCommanderxXx]

"Dropping loads"

[@ayra_c3781]

Just like everyday

[@davidsan9654]

Dropping loads more often is my new favorite SciShow quote

[@testament0]

Came here to learn, stayed for dropping loads more often.

[@bjm6275]

Well said about voicing conclusions, even from scientific findings.

[@iftruth]

Nobody: 2020: Well let me introduce bats to you

[@cookeymonster83]

Bats aren't wrong They don't fly into people's mouths

[@TheRABIDdude]

Summary: Bats: Might be to limit weight (for flight), or because their very rapid digestive transit doesn't pair well with bacterial growth, or due to a non-accomodating immune system (evolved due to flight). Birds also have limited gut microbiomes. Caterpillars: have very alkaline (bleach level) digestive tracts which are inhospitable to bacteria. Might have evolved to ditch the risk of infection in favour of eating huge volumes of plant and only accessing minimal nutrition. Ants: some have microbiomes, others don't. Some ants lace their nests with antimicrobials to keep them clean, and so might have had to evolve to get by without a microbiome due to constant antimicrobial ingestion. Some ants are very temperature resistant, so might have evolved to ditch their more temperature-sensitive microbiomes which hold them back (creating digestive issues) from expanding into different climates/temperatures. Some ants might have ditched microbiomes because they eat a lot of non-plant food, which is much easier to digest. Stick insects got lucky by accessing bacterial digestive genes by horizontal gene transfer in their evolutionary history. They've adopted, amplified and refined these genes, so now they indiscriminately prevent all microbial entrance using aggressive antimicrobials. They are the only 100% vegetarian order of insects. He also sort of implies that perhaps their extremely thin shape is only possible because they don't need to leave space in their digestive tract for microbial communities.

[@spindash64]

I also notice a suspicious lack of greens in the diets of bats and birds, at least that I’m aware of. Probably both because they don’t have a gut microbiome to help, and they don’t have a biome for it because they don’t chow on that stuff

[@TheRABIDdude]

@@spindash64 Hmm yeah, that's true, you rarely see birds that have evolved to just sit and eat leaves all day! As well as your reasons why eating greens making flight difficult, I would argue the reverse argument reasoning is also true: flight doesn't make eating green easier. The energetically demanding adaptations for flight are wasted/uneeded if the animal's food is abundant and non-moving (i.e. greens). Waterbirds like ducks and geese are the only birds I'm aware of that don't fit the bill (pun intended) as they eat primarily greens. As these are much larger animals, I suspect they do have space for microbiomes full of commensal bacteria to help out.

[@KnighteMinistriez]

I like learning. Science is awesome. Keep up the good work.

[@kaitygeer1570]

This is so cool to learn.👍

[@panostriantaphillou766]

a. what do you feed brine shrimps in sweet water? (an example could be illuminating). b. does the temperature influence the microbiome of humans who also live in widely different climatic areas? c. what research is done on the various natural antibiotics of all the animals presented?

[@afaqayub6320]

I really like this guy personality.

[@muraxesis]

It sounds like I should be dropping loads more often...

[@ViniSocramSaint]

Maybe carterpillars fight gut flora cuz it would eat them from inside out alive when they dissolve trying to turn into a butterfly

[@Kavriel]

Stick insects are actually fascinating ! Could we get that cellulose digesting enzymes gene and make some horizontal gene transfer to our own genome, and how could it change our diets ?

[@RustyTube]

That’s pretty gutsy of them!

[@mikel6668]

great video

[@RainAngel111]

This reminds me of the original primate video from Tierzoo. He originally talked about the microbiome as if it was a uniquely human adaptation. I actually didn't know there are some species without a microbiome.

[@swmtothemoon6660]

"Dropping loads" I'm dead

[@ryco105]

Yoooooo

[@Nobody_Special310]

These are some strong, independent animals who don't need no microbiomes.

[@keithharper32]

So, both bats and birds have fast digestive tracts that make limited use f microbes. I wonder if this has implications fr the physiolgy of pterosaurs

[@InterstinglyGeneric]

this channel been here for so long

[@jupitersart7106]

good job

[@alterego3734]

It makes sense for faster-evolving animals to integrate vertically rather than outsource digestion.

[@jansenart0]

One might say that pink substance fuschin was... fuschia.

[@Amenhotepish]

Very interesting. Thanks :-)

[@blackmancer]

1. Hows about the bats and birds, through evolution, required quicker digestion, ie in a flock, those who pooped quicker got to fly off a little bit before the full tummies and didn't get eaten. I'm guessing that pooping quicker not only triggers the body to digest quicker (in bats and birds) but also then gives less time for bacteria to do its thing and leads to a situation of quick pooping (better uptake) low bacteria count digestive systems

[@scottmantooth8785]

*it's when you have to remember all of their individual names that things become awkward socially*

[@Bloodshotistic]

Never thought I'd have "pink bat poop" in my search history but here... we... are...

[@pedroff_1]

"but they're not full of gratitude. They're full of antibiotics"

[@Bimtavdesign]

I died

[@woodfur00]

Imagine you were an alien with no gut biome, and you heard this guy talking about how scientifically fascinating it is that these strange outliers don't rely on a personal ecosystem of microorganisms to digest their food, or maybe they actually do and we just haven't found them yet. I mean, it would be almost comically stereotypical, a parody of things scientists who are too sure of themselves say. I love that.

[@siftindotcom]

Question: How is convalescent plasma used as a drug for COVID-19? Can it be used as a vaccine as well?

[@ShubhamSharma-dq3cq]

Michael having Bermuda triangle on his face...lmao

[@anuragdas9509]

He's adopting more amd more of a "good boy" look. He's even combing his hair now lol.

[@lakeratatouille]

Bats are hard to digest especially the aluminum variety I'll stick with the Louisville strain.

[@keirfarnum6811]

Bleau Hartley 😂😂😂😂😂

[@Neuralatrophy]

Rapid consumption, digestion and elimination could be at least part of the cause of thier lack of gut bacteria. Humans suffering diarhea can have depleated gut bacteria.

[@massimookissed1023]

There seems to be some myth that caterpillars dissolve onto goo before reforming as a butterfly.

[@pauldeddens5349]

They for the most part liquify, but people definitely are exaggerating the actual process

[@patrickmccurry1563]

Or just from a few posters that keep repeating the over simplification. Caterpillars do mostly liquify. But they certainly maintain their nervous system integrity throughout the process.

[@yabasta13]

God I love this show.

[@Gothead420]

0:25: looks like somebody ate too many pills...

[@cele42]

Michael is 🔥

[@KLFD530]

1:42 bats are like me on Saturday night.

[@jaschabull2365]

I'm just picturing caterpillars being very confused at why suicidal humans always talk about wanting to drink bleach. Hmm, maybe a suicidal caterpillar would want to drink lemonade instead?

[@malavoy1]

That first image looked less like gut microbes and more like someone ate a big box of Good N Plenty D~

[@pitterpatter7719]

Seems to imply eating stick bugs might be a good idea in austere settings if infection is an issue

[@Sara3346]

...but not caterpillars if their full of stuff equivalent to bleach I don't want that in me.

[@fireandcopper]

5:46 explains why I can only drink 2 brand names of beer, I could drink more but the effects of them are undesirable

[@bjrockensock]

Say tummy, Michael. You have a beautiful voice.

[@joshantebi4126]

I hear that all the time

[@garchompy_1561]

Surely the reason Caterpillars dont have bacteria in their gut is because they completely "dissolve"(?) During metamorphosis and any bacteria would just get in the way during the process.

[@Treblaine]

3:20 a.k.a. "Basic AF"

[@twothreebravo]

"Super Basic Caterpillar Gut Juices" I think that's a 3rd Wave Ska band

[@Scribe13013]

That's what I call a sticky situation

[@irvingchies1626]

So i guess now I know why during summer I fart so much and during winter so little, I guess my gut bacteria become crazy

[@theshuman100]

bats: have no gut bacteria also bats : literally a reservoir for viruses

[@EduardQualls]

My gut bacteria after Tex-Mex: Welcome to another edition of Thunder Biome!

[@arthas640]

Tex-Mex is an entry level gut bomb, try eating expired thai curry.

[@uhohhotdog]

More gut bacteria would weigh you down? So I’m not fat I just have a lot of gut bacteria.

[@SovereignwindVODs]

@Ben Louis no i'm pretty sure he literally means weight. something like a third of our mass comes from the microbes in our guts. I may be overestimating that proportion, but I remember it was significantly larger than I was expecting when I heard it.

[@laurachapple6795]

If it's related to flight, odds are pterosaurs didn't have much for gut flora, either. If only there were some way to check.

[@ezpzwins7613]

Can you make an episode on trigeminal neuralgia

[@MephLeo]

It takes guts to study this.

[@marcopohl4875]

This is going to make it difficult for fantasy writers, trying to make scientifically accurate dragons: a common explanation for fire breath is that they use digestive gas as fuel, but they might not have as much or no reliable supply if they don't have gut bacteria, which flying animals, like them, usually don't

[@TheExoplanetsChannel]

*Thumbs up if SciShow is your favourite channel about science!*

[@juliamichelle2770]

Aren't you a science channel

[@nitish18tayal]

The loss of microbiome in flying species can be the result of adapting to fast digestion to reduce body weight while flying. Any microbial action takes time and more a species depend on microbes more time they take to digest with rumens taking a lot of time and regurgitating food again and again... So in a setting where food needs to be digested quickly microbes are little to no help...

[@julianadelicato7715]

Michael ♥️

[@sprinkhole58]

You could say they take the poop crown... a poop CORONA.

[@shaunpattinson1621]

“Dropping loads.....” 🤣🤣🤣

[@onlypranav]

1:49 "A large population of microbes might weigh them down". Huh? That's weird.. Didn't expect them to weigh any significant amount.

[@geek2thextreme]

what about flighted bugs like dragon flies?

[@honeymon131415]

I relate to these animals. I feel like my body has ditched my microbes.

[@Zahri8Alang]

How about that caterpillar you guys covered before that's capable of digesting plastic?

[@mechasentai]

Notification squad y'all!

[@secret12392]

I knew most insects weren’t pure vegetarians, but it’s just... oddly terrifying to be reminded of it.

[@andrewbrown6522]

I was completely under the impression that complex life requires the bionome. Ive even wondered if micro extinctions and blooms could be responsible for macro extinctions. Likewise i put the likelihood of bringing extinct species back for lack of support systems.

[@rickvbeck1]

Has anyone figured out just what the *** happens during the metamorphosis of a butterfly?

[@baraskparas9559]

One additional reason could be the small size of bats and little birds make gut microbiomes real competitors for the nutrients in the food. Those with smaller microbiomes are selected for. Caterpillars don't need competition due to their required growth rate. Stick insects need to spend most of their time pretending to be sticks or leaves so they don't need the competition of microbiomes.

[@yvessioui2716]

Is it a guess or not from me? May be it should have been a good idea to prove that situation (A) is not phylogenetic and (B) is proven to be seen that way. As for (B), why not the reverse, most ancient animals didn't have any help from microbe so some keep getting rid of them and some develop a partnership with some microbes. Looks to me probable because we find microbiome more on new plyla than older one.

[@briea8291]

How would you like it if caterpillars called YOU super basic? 😤😤😤 😢😢😢 😂😂😂