WEBVTT - What Colors Can Blood Be Other Than Red?

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<v Speaker 1>Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff

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<v Speaker 1>Laurin bolabahm here. Red elicits strong reactions around the world.

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<v Speaker 1>It is by far the most commonly used color in

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<v Speaker 1>national flags. It can be a major confidence booster. Researchers

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<v Speaker 1>have found that wearing red garments makes people feel more attractive.

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<v Speaker 1>On the flip side, according to one study from twenty thirteen,

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<v Speaker 1>looking at red things might cause us to experience pain

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<v Speaker 1>more intensely. Maybe red wouldn't provoke our brains so much

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<v Speaker 1>if it didn't happen to be the color of human blood.

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<v Speaker 1>In this regard, Homo sapiens is far from unique. From

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<v Speaker 1>timberwolves to tiger sharks, most vertebrate animals have crimson colored

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<v Speaker 1>blood in their veins. This hue is produced by hemoglobin,

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<v Speaker 1>the protein that helps our blood distribute oxygen around our bodies.

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<v Speaker 1>Read school, you probably learned that blood contains three types

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<v Speaker 1>of cells. White blood cells help us fight off viruses,

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<v Speaker 1>harmful bacteria, and other pathogens. Then we've got platelets, the

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<v Speaker 1>damage control specialists that allow our blood to clot. A Last,

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<v Speaker 1>but certainly not least, we've got red blood cells. Their

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<v Speaker 1>main purpose is to carry around oxygen from and take

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<v Speaker 1>away carbon dioxide to the lungs, where these gases are

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<v Speaker 1>inhaled and exhaled, respectively. The protein hemoglobin lets these cells

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<v Speaker 1>execute both tasks, a core ingredient in red blood cells,

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<v Speaker 1>hemoglobin combined to oxygen and carbon dioxide. Hemoglobin is partly

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<v Speaker 1>made up of iron atoms, which give this protein, and

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<v Speaker 1>by extension, are red blood cells a crimson color. Since

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<v Speaker 1>our platelets and white blood cells are vastly outnumbered by

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<v Speaker 1>red blood cells, human blood as a whole looks red,

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<v Speaker 1>but like many things, blood exists on a spectrum due

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<v Speaker 1>to the pressures of evolution. We've got everything from blue

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<v Speaker 1>blooded invertebrates to green blooded reptiles to fish with transparent

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<v Speaker 1>fluids in their veins. Today, let's talk about some of

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<v Speaker 1>the curious critters with blood in colors other than red.

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<v Speaker 1>First up, New Guineas green blooded skinks. New Guineas home

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<v Speaker 1>to multiple lizard species from the skink family that have

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<v Speaker 1>line green blood. Consequently, their tongues, muscles, and bones are

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<v Speaker 1>all various shades of green. Like humans, reptiles have hemoglobin

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<v Speaker 1>rich red blood cells, but such cells do not live forever,

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<v Speaker 1>and when they break down in our bodies as well

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<v Speaker 1>as the lizards, a green pigmented waste product called biliverdin

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<v Speaker 1>is created. Most vertebrates filter this stuff out of their

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<v Speaker 1>circulatory systems because excess biliverdin can harm cells, including neurons

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<v Speaker 1>and DNA. These lizards have a level of verdin in

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<v Speaker 1>their veins that would kill a human. Moreover, the pigment

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<v Speaker 1>is so densely concentrated that it overrides the hemoglobin and

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<v Speaker 1>makes their blood look green. Herpetologists aren't entirely sure why

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<v Speaker 1>these lizards possess this trait, but it's apparently a strong one.

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<v Speaker 1>In a study published in twenty eighteen, researchers carried out

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<v Speaker 1>a genetic survey of fifty one different skinks in Australia, Asia,

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<v Speaker 1>and the Islands between them. They analyzed six of the

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<v Speaker 1>green blooded New Guinea species in the process. It turns

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<v Speaker 1>out that those biliverden loaded reptiles aren't even closely related

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<v Speaker 1>to one another. It seems that each of them is

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<v Speaker 1>descended from red blooded ancestors, and they evolved green bloodedness independently.

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<v Speaker 1>Such an unusual trait wouldn't have evolved six times over

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<v Speaker 1>if it didn't offer some kind of benefit. But again

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<v Speaker 1>we're not sure what it is. Predators that eat the

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<v Speaker 1>lizards don't get sick afterward, and the skinks are no

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<v Speaker 1>better camouflaged than their red blooded cousins. It's possible that

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<v Speaker 1>the special blood helped their ancestors kill parasites, but more

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<v Speaker 1>research will be needed to confirm or refute this. While

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<v Speaker 1>we're waiting on that, let's move on to the crocodile

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<v Speaker 1>ice fish, so named for their long toothy snouts. The

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<v Speaker 1>sixteen species of crocodile ice fish that have been recognized

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<v Speaker 1>all live in the ocean waters around in Arctica. These

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<v Speaker 1>extremophiles are built to thriving conditions that would kill most

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<v Speaker 1>other vertebrates. They frequent brutally cold areas where the water

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<v Speaker 1>temperature can plummet all the way down to twenty eight

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<v Speaker 1>degrees fahrenheit or negative two celsius. That's below the point

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<v Speaker 1>at which freshwater freezes. In such cold water, red blood

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<v Speaker 1>cells turn into a liability. That's because blood with the

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<v Speaker 1>high percentage of these cells becomes dangerously thick and hard

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<v Speaker 1>to circulate when the temperature gets too low. A fish

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<v Speaker 1>that thrive in cold waters tend to have proportionately fewer

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<v Speaker 1>red blood cells than their warm water counterparts do. But

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<v Speaker 1>crocodile ice fish take this to the extreme. Unlike every

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<v Speaker 1>other known type of vertebrate animal, they don't have any

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<v Speaker 1>red blood cells or hemoglobin at all. Now you might

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<v Speaker 1>be thinking, wait a second. Without hemoglobin or red blood cells,

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<v Speaker 1>how do the fish circulate oxygen through their bodies. To

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<v Speaker 1>get the job done? They enlist the ocean itself. Cold

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<v Speaker 1>water is naturally richer in usable oxygen than warm water.

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<v Speaker 1>Crocodile ice fish absorbs above this oxygen directly from the

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<v Speaker 1>ocean around them and send it into their blood streams.

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<v Speaker 1>The blood itself is a colorless liquid, a fact that

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<v Speaker 1>really surprised the biologists who discovered these fish in nineteen

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<v Speaker 1>twenty eight. It turns out that this cold water oxygen

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<v Speaker 1>is so abundant that, upon absorption, it doesn't need to

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<v Speaker 1>hitch a ride on red blood cells to get around. Instead,

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<v Speaker 1>it can travel from point A to point B inside

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<v Speaker 1>the fish's plasma hemoglobin free. But okay, As so far

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<v Speaker 1>we've been talking about vertebrate animals, which nearly all use

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<v Speaker 1>hemoglobin to circulate oxygen. Many invertebrates use an alternative protein,

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<v Speaker 1>hemocyanin both are capable of binding to and transporting oxygen.

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<v Speaker 1>But whereas hemoglobin contains iron atoms, hemocyanin incorporates copper. As

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<v Speaker 1>a result, blood containing hemocyanin looks markedly different from our

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<v Speaker 1>human blood. When hemocyanin rich blood becomes oxygenated, the copper

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<v Speaker 1>in it turns it blue. The list of invertebrates that

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<v Speaker 1>rely on hemocyanin instead of hemoglobin is a long one,

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<v Speaker 1>including crustaceans, spiders, and scorpions. The roster also includes certain mollusks,

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<v Speaker 1>like everyone's favorite multi armed brainiacs, octopuses. Yes, octopuses have

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<v Speaker 1>literally blue blood and three hearts with which to pump

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<v Speaker 1>it in oxygen poor deep sea environments, hemicyanin is better

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<v Speaker 1>than hemoglobin, carrying that precious oxygen through in animal's veins.

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<v Speaker 1>Octopuses use the protein to stay alive in some seriously

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<v Speaker 1>deep waters and at a wild range of temperatures, from

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<v Speaker 1>what would be below freezing in fresh water to superheated

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<v Speaker 1>near thermal vents. Additionally, hemicyanin helps these tentacled critters regulate

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<v Speaker 1>the salt content of their blood so that it matches

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<v Speaker 1>that of the water that they're swimming. In next up brachiopods.

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<v Speaker 1>These are ocean dwelling animals that resemble clams, though they

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<v Speaker 1>evolved independently. Braccupods grow a pair of shells around the

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<v Speaker 1>upper and lower surfaces of their squishy bodies, connected with

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<v Speaker 1>a hinge at one end, a found in an assortment

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<v Speaker 1>of marine habitats. The creatures filter tiny food particles out

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<v Speaker 1>of the water. Although there are over three hundred living species,

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<v Speaker 1>most people is so brachiopods with prehistoric times because these

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<v Speaker 1>hard shelled creatures are disproportionately well represented in the fossil record.

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<v Speaker 1>Extant brachiopods do not rely on either hemoglobin or hemocyanin

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<v Speaker 1>to ferry oxygen in the blood. Instead, they have heemerthrine,

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<v Speaker 1>yet another pigmented protein. Like hemoglobin, it contains iron atoms,

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<v Speaker 1>albeit in a different arrangement. Heemerythrine makes deoxygenated blood look colorless,

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<v Speaker 1>too faintly yellow. Once the blood starts taking on oxygen,

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<v Speaker 1>it adopts a violet, pinkish hue. You'll also see this

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<v Speaker 1>kind of blood in marine worms in the class Sypuncula.

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<v Speaker 1>They're nicknamed peanut worms because some of them have bodies

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<v Speaker 1>that grow in small pointed ovals, looking a bit like

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<v Speaker 1>shelled peanuts. These buddies often reside in shallow waters, burrowing

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<v Speaker 1>in sand or mud, or taking up in crevices or

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<v Speaker 1>unoccupied shells. Other ocean going worms have a different circulatory setup.

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<v Speaker 1>If a diver were to spot a live polyket cruising

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<v Speaker 1>through the waves, they might mistake it for a sentient

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<v Speaker 1>feather duster. Most of these worms are covered in bristles

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<v Speaker 1>and tentacles, whose function varies from species to species. Some

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<v Speaker 1>have red blood, but others harbor green blood. The latter

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<v Speaker 1>use the oxygen binding protein chlorocrurine in place of hemoglobin.

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<v Speaker 1>It also uses iron to bind to oxygen, but in

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<v Speaker 1>yet another formation, it's what's called dichroic, or too colored,

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<v Speaker 1>which means that it can appear to be different colors

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<v Speaker 1>in different circumstances. When chlorocrurine is concentrated, its molecules stack

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<v Speaker 1>to appear deep red brown, but when it's dilute it

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<v Speaker 1>appears green, which means that even if Kermit was right,

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<v Speaker 1>and it's not easy being green, at least those new

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<v Speaker 1>guinea skinks have some creepy Crawley Company. Today's episode is

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<v Speaker 1>based on the article Five Animals whose Blood Isn't read

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<v Speaker 1>on HowStuffWorks dot Com, written by Mark Mancini. Brain Stuff

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<v Speaker 1>is production of iHeartRadio in partnership with HowStuffWorks dot Com

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<v Speaker 1>and is produced by Tyler Klang. Four more podcasts my

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<v Speaker 1>heart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever

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<v Speaker 1>you listen to your favorite shows.