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There are creatures who get some super important and recognizable part of their biology from their diets.

Hosted by: Michael Aranda

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Blue-footed booby
Poison frogs
Assassin bugs
Halophilic protists
Stoplight loosejaw
Solar sea slug
Blue dragon nudibranch
Thanks to Skillshare for supporting this episode of SciShow. [ ♪ Intro ].

At some point in your life, you’ve probably heard someone say, “you are what you eat.” Like, when your parent saw you wash down an entire pizza with a 2-liter bottle of whatever your caffeinated beverage of choice is. Or you watched Violet Beauregarde turn into a giant blueberry.

Well, it turns out there are creatures out there in the real world who do get some super important and recognizable part of their biology from their diets. From single-celled organisms to terrifying dragonfish, here are seven life forms that take the phrase “you are what you eat” to heart...or stomach. A lot of birds get their coloration from their diets, but perhaps the most striking is the blue-footed booby.

Named for, well, you know… its blue feet. These seabirds are found in the Galapagos and along the western coasts of Central and South America. And despite the name, their feet actually range from dull blue to bright green.

The color comes from a combination of the structural protein fibers in their feet and carotenoids, pigment proteins similar to the ones that make carrots orange and flamingos pink. Animals can’t make carotenoids themselves, they have to get them from their diets. In the blue-footed booby’s case, they come from fish like anchovy and sardines, which in turn get them from the stuff they eat.

Studies have shown that a lack of fish not only dulls a male’s feet, it also lowers his immune defenses. That means vibrant feet are what scientists call an honest signal of a booby’s hunting success and health. That’s probably why the courting dance for these birds is all about showing off those colorful toes.

And it’s not just the males saying “Look at my bright feet, ladies! I’m healthy and can feed you!” Females get judged by their feet, too. Males spend less time incubating the eggs of dull-footed females, unless those eggs are large enough to show that the female put extra investment into their chick.

Speaking of vibrant color, you’ve probably heard of poison frogs, or as they’re sometimes called poison dart frogs, even though only a few species of the couple hundred in the family Dendrobatidae seem to have actually been used that way. The thing is, as far as we know, none of them actually make the toxins they’re named for. A poison frog’s potency is due to the special mix of alkaloids that it gets from munching on critters like beetles, ants and millipedes.

Alkaloids are high-pH, or basic, compounds that contain nitrogen atoms. And you’ve certainly heard of some, like caffeine, nicotine, and morphine. One of the deadliest is batrachotoxin, which is found in really high concentrations in the skin glands of the most toxic poison frogs.

It jams open channels in your cell membranes that let sodium ions cross over, and that jamming causes muscle contractions, heart palpitations, and even cardiac arrest. Thanks to a single mutation in their own sodium ion channels, the frogs can resist these effects. It’s unknown how poison frogs resist other alkaloids; some researchers suspect they may just break them down faster than we do.

It’s also not really known how these toxins move from stomach to skin glands, but whatever happens, it allows the frogs to store them for years. And some mother frogs actually feed their tadpoles with alkaloid-laden unfertilized eggs so they become poisonous long before they can wrangle bugs. But unless you’re trekking through rainforests in Central and South America, any poison frogs you’ve seen are probably harmless.

Captive poison frogs usually aren’t fed the same toxic diet as their wild counterparts, so they’re pretty, but no longer pretty deadly. Assassin bugs are so named because they’re prolific hunters. But some young assassin bugs take that reputation to a whole ‘nother level.

They don’t just kill, they wear the bodies of their victims as a kind of corpse armor. Assassin bug nymphs hunt a variety of prey, but ants have a special fate. They pierce the ants’ exoskeleton with their sharp mouth parts, and inject a paralyzing saliva and digestive enzymes which dissolve the ant’s interior tissues into delicious, slurp-able smoothies.

Then, instead of discarding the newly hollow husks, the bugs fashion them into tasteful outerwear. They can carry the corpses of up to 20 ants at once, and the cluster can be bigger than their entire body! Some researchers have suggested that they make these adornments to provide a kind of smell-based camouflage so they can sneak up on future meals.

Others say it’s so predators don’t recognize them as prey, and there’s some evidence to back that idea up. A 2007 study found that jumping spiders, which have a poor sense of smell, but really good vision, attacked naked bugs roughly 9 times more frequently than the ones sporting ant camo. Of course, that doesn’t mean the dead ants don’t help hide the bug’s smell, too.

Like the best items in your wardrobe, corpse armor could have multiple uses. Halophilic heterotrophic protists are single-celled organisms that eat bacteria and live in super salty ponds, like the ones we make for harvesting sea salt. The salt in such waters can vary a lot, and that’s not good for living things.

So to survive, these protists have stolen genes from their food. Saltiness is a problem because it makes it tough to control the water content of cells. If there’s less salt on the outside of a cell, a lot of water will get pushed into the cell, eventually popping it like a balloon.

When the water outside a cell has more salt, like in these super salty ponds, then the water inside the cell leaves in a futile attempt to balance things out, turning the cell into a sort of pickled raisin. Luckily, a handful of protists have found a way to survive their saline sanctuaries: special compounds like ectoines that help them stay hydrated. Ectoines can accumulate in great numbers inside a cell without disrupting the normal goings-on.

So they’re really good at preventing cells from getting damaged as water gets pushed into or out of them. At first, the protists probably just stole these ecotines from the bacteria they ate. But then, at some point, they actually stole the genes that the bacteria use to create the ectoines in the first place, and incorporated them into their own DNA.

It’s a phenomenon known as horizontal gene transfer, and is really popular with bacteria, but is much rarer in protists and other species that protect their genome in a membrane-bound nucleus. Deep in the darkness at 500 to 1000 meters below sea level, the pitch-black stoplight loosejaw hunts. This dragonfish is able to see things others that dwell in the deep can’t because it can pick up on deep red and near-infrared light.

But it doesn’t have that ability innately. It gets it from its meals. The gaping maws of dragonfish are well equipped for snacking on other fish, and the stoplight loosejaw is no exception.

But a lot of the time, their fare is much smaller: zooplankton. When scientists have dissected these fish’s stomachs to see what’s in them, large calanoid copepods can comprise up to about half of the contents by weight. These copepods are 1000 times more abundant down at the loosejaw’s hunting depths than the fish or shrimp they might otherwise eat, so it makes sense that they snack on them while searching for bigger meals.

But they don’t just eat them for the extra calories. They supply stoplight loosejaws with the pigment that allows them to perceive deep red and near-infrared light. Most fish at deeper depths are only really sensitive to short, blue and green wavelengths of light because longer wavelengths just don’t make it that far down.

But the loosejaw doesn’t rely on rays from the sun, it can produce deep red light in special light-producing organs beneath its eyes. And it even wouldn’t be able to see that light if it weren’t for the usual pigment it probably gets from copepods. There are some details that still need to be ironed out, but because the pigment is similar to one found in a species of bacteria, scientists think the copepods get the pigment from bacteria they eat, and then pass it along when they get eaten by the dragonfish.

The eastern emerald elysia sea slug stands out as one of relatively few animals that can live off of light like a plant. But, spoiler! that’s a unique trait they get from their food. Juveniles off the eastern coast of North America eat a bunch of different species of algae.

But starting as young adults, they focus on one. And as they munch away, they actually take the algae’s chloroplasts, the organelles in their cells responsible for photosynthesis, and store them in pouches in their digestive tract. Remarkably, they can actually use those chloroplasts to run on solar power.

In fact, experiments have shown they can go without eating for over nine months! We don’t currently know they keep these sun-harnessing tools running, though. Chloroplasts need proteins made by other parts of a cell to function, parts that animals don’t generally have.

Some scientists think the slug stole algal genes a long time ago, kind of like the protists we talked about earlier, but other studies have suggested that’s not the case, and it just uses the relevant bits of DNA without putting them into its genome. Somehow. We also don’t really know why the slug’s stomach or immune system doesn’t just destroy the foreign cell parts.

Though studies have found that the animals express different genes when exposed to the algae, including ones that change how their bodies respond to foreign cells. And we don’t even know if they really need to be solar powered. Research from 2014 found that these slugs can actually survive in the dark and when injected with chemicals that inhibit photosynthesis.

A lot of these questions could be answered with further studies, but unfortunately, their populations are dwindling and it’s tough to raise them in captivity, so very little research is being conducted on them now. The blue dragon nudibranch is known for its vibrant color. It spends its days floating on the ocean surface hoping to run into something tasty to eat, like Portuguese Man o’ War.

You’d think these squishy little slugs would be easy pickings for other ocean predators, but they’re not as defenseless as they seem, thanks to their toxic diet. Like other Aeolid nudibranchs, as larvae, they have shells, but they lose them as they grow into adults. Without that shell for protection, they have to find another way to keep predators from gobbling them up.

And they do that by stealing special toxin-delivering cells called cnidocytes, from their food. Inside each cnidocyte is a stinging tool called a nematocyst. It has a small trigger hair that sticks outside the cell.

When something brushes it, like a large fish looking for a meal, water rushes into the cell. The pressure change causes a toxic harpoon to shoot into the offender. Luckily for blue dragons and their cousins, they’ve developed adaptations to defend themselves against their preys’ stings.

Depending on the species of nudibranch, some have mucus, and some have hard chitin plates inside their mouth, throat, and digestive tract that the stingers can’t penetrate. Some of the stinging cells that don’t get triggered are pushed through the walls of the nudibranch’s gut into appendages called cerata. There, they’re stored in special sacs until they’re used.

And just like the poison frogs, these nudibranchs are vibrantly colored, a signal for predators to stay away. Taking on the properties of your food is really just another cool way nature has managed to adapt to a situation. Need help hunting?

Boom! See light none of your neighbors can. Need help not being hunted?

Bam! Stab them with toxic needles. So you might be feeling a little jealous you don’t get any cool physical properties from chowing down on last night’s leftovers.

But maybe that’s a good thing. At least it is for me, because my diet is like 90% junk food. Now, in my defense, cooking can take a really long time.

Which is why I’m glad that Skillshare has me covered. Skillshare has a class called Quick and Healthy Dinner for (Really) Busy People, taught by food bloggers Ceri Marsh and Laura Keogh. It teaches you how to make easy and fast dinners that are also good for you, even if they don’t give you cool traits like the species in this episode.

The class feels like a good reminder that there are always new things to learn, even when it comes to something as simple as cooking. And since Skillshare has more than 20,000 classes about everything from sewing to animation, there’s also a lot more to explore. Right now, Skillshare is offering SciShow viewers 2 months of unlimited access to all of their classes for free.

You can follow the link in the description to check it out! [ ♪ Outro ].