Speaker 1: Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff
Speaker 1: Laurin bolabahm here. Red elicits strong reactions around the world.
Speaker 1: It is by far the most commonly used color in
Speaker 1: national flags. It can be a major confidence booster. Researchers
Speaker 1: have found that wearing red garments makes people feel more attractive.
Speaker 1: On the flip side, according to one study from twenty thirteen,
Speaker 1: looking at red things might cause us to experience pain
Speaker 1: more intensely. Maybe red wouldn't provoke our brains so much
Speaker 1: if it didn't happen to be the color of human blood.
Speaker 1: In this regard, Homo sapiens is far from unique. From
Speaker 1: timberwolves to tiger sharks, most vertebrate animals have crimson colored
Speaker 1: blood in their veins. This hue is produced by hemoglobin,
Speaker 1: the protein that helps our blood distribute oxygen around our bodies.
Speaker 1: Read school, you probably learned that blood contains three types
Speaker 1: of cells. White blood cells help us fight off viruses,
Speaker 1: harmful bacteria, and other pathogens. Then we've got platelets, the
Speaker 1: damage control specialists that allow our blood to clot. A Last,
Speaker 1: but certainly not least, we've got red blood cells. Their
Speaker 1: main purpose is to carry around oxygen from and take
Speaker 1: away carbon dioxide to the lungs, where these gases are
Speaker 1: inhaled and exhaled, respectively. The protein hemoglobin lets these cells
Speaker 1: execute both tasks, a core ingredient in red blood cells,
Speaker 1: hemoglobin combined to oxygen and carbon dioxide. Hemoglobin is partly
Speaker 1: made up of iron atoms, which give this protein, and
Speaker 1: by extension, are red blood cells a crimson color. Since
Speaker 1: our platelets and white blood cells are vastly outnumbered by
Speaker 1: red blood cells, human blood as a whole looks red,
Speaker 1: but like many things, blood exists on a spectrum due
Speaker 1: to the pressures of evolution. We've got everything from blue
Speaker 1: blooded invertebrates to green blooded reptiles to fish with transparent
Speaker 1: fluids in their veins. Today, let's talk about some of
Speaker 1: the curious critters with blood in colors other than red.
Speaker 1: First up, New Guineas green blooded skinks. New Guineas home
Speaker 1: to multiple lizard species from the skink family that have
Speaker 1: line green blood. Consequently, their tongues, muscles, and bones are
Speaker 1: all various shades of green. Like humans, reptiles have hemoglobin
Speaker 1: rich red blood cells, but such cells do not live forever,
Speaker 1: and when they break down in our bodies as well
Speaker 1: as the lizards, a green pigmented waste product called biliverdin
Speaker 1: is created. Most vertebrates filter this stuff out of their
Speaker 1: circulatory systems because excess biliverdin can harm cells, including neurons
Speaker 1: and DNA. These lizards have a level of verdin in
Speaker 1: their veins that would kill a human. Moreover, the pigment
Speaker 1: is so densely concentrated that it overrides the hemoglobin and
Speaker 1: makes their blood look green. Herpetologists aren't entirely sure why
Speaker 1: these lizards possess this trait, but it's apparently a strong one.
Speaker 1: In a study published in twenty eighteen, researchers carried out
Speaker 1: a genetic survey of fifty one different skinks in Australia, Asia,
Speaker 1: and the Islands between them. They analyzed six of the
Speaker 1: green blooded New Guinea species in the process. It turns
Speaker 1: out that those biliverden loaded reptiles aren't even closely related
Speaker 1: to one another. It seems that each of them is
Speaker 1: descended from red blooded ancestors, and they evolved green bloodedness independently.
Speaker 1: Such an unusual trait wouldn't have evolved six times over
Speaker 1: if it didn't offer some kind of benefit. But again
Speaker 1: we're not sure what it is. Predators that eat the
Speaker 1: lizards don't get sick afterward, and the skinks are no
Speaker 1: better camouflaged than their red blooded cousins. It's possible that
Speaker 1: the special blood helped their ancestors kill parasites, but more
Speaker 1: research will be needed to confirm or refute this. While
Speaker 1: we're waiting on that, let's move on to the crocodile
Speaker 1: ice fish, so named for their long toothy snouts. The
Speaker 1: sixteen species of crocodile ice fish that have been recognized
Speaker 1: all live in the ocean waters around in Arctica. These
Speaker 1: extremophiles are built to thriving conditions that would kill most
Speaker 1: other vertebrates. They frequent brutally cold areas where the water
Speaker 1: temperature can plummet all the way down to twenty eight
Speaker 1: degrees fahrenheit or negative two celsius. That's below the point
Speaker 1: at which freshwater freezes. In such cold water, red blood
Speaker 1: cells turn into a liability. That's because blood with the
Speaker 1: high percentage of these cells becomes dangerously thick and hard
Speaker 1: to circulate when the temperature gets too low. A fish
Speaker 1: that thrive in cold waters tend to have proportionately fewer
Speaker 1: red blood cells than their warm water counterparts do. But
Speaker 1: crocodile ice fish take this to the extreme. Unlike every
Speaker 1: other known type of vertebrate animal, they don't have any
Speaker 1: red blood cells or hemoglobin at all. Now you might
Speaker 1: be thinking, wait a second. Without hemoglobin or red blood cells,
Speaker 1: how do the fish circulate oxygen through their bodies. To
Speaker 1: get the job done? They enlist the ocean itself. Cold
Speaker 1: water is naturally richer in usable oxygen than warm water.
Speaker 1: Crocodile ice fish absorbs above this oxygen directly from the
Speaker 1: ocean around them and send it into their blood streams.
Speaker 1: The blood itself is a colorless liquid, a fact that
Speaker 1: really surprised the biologists who discovered these fish in nineteen
Speaker 1: twenty eight. It turns out that this cold water oxygen
Speaker 1: is so abundant that, upon absorption, it doesn't need to
Speaker 1: hitch a ride on red blood cells to get around. Instead,
Speaker 1: it can travel from point A to point B inside
Speaker 1: the fish's plasma hemoglobin free. But okay, As so far
Speaker 1: we've been talking about vertebrate animals, which nearly all use
Speaker 1: hemoglobin to circulate oxygen. Many invertebrates use an alternative protein,
Speaker 1: hemocyanin both are capable of binding to and transporting oxygen.
Speaker 1: But whereas hemoglobin contains iron atoms, hemocyanin incorporates copper. As
Speaker 1: a result, blood containing hemocyanin looks markedly different from our
Speaker 1: human blood. When hemocyanin rich blood becomes oxygenated, the copper
Speaker 1: in it turns it blue. The list of invertebrates that
Speaker 1: rely on hemocyanin instead of hemoglobin is a long one,
Speaker 1: including crustaceans, spiders, and scorpions. The roster also includes certain mollusks,
Speaker 1: like everyone's favorite multi armed brainiacs, octopuses. Yes, octopuses have
Speaker 1: literally blue blood and three hearts with which to pump
Speaker 1: it in oxygen poor deep sea environments, hemicyanin is better
Speaker 1: than hemoglobin, carrying that precious oxygen through in animal's veins.
Speaker 1: Octopuses use the protein to stay alive in some seriously
Speaker 1: deep waters and at a wild range of temperatures, from
Speaker 1: what would be below freezing in fresh water to superheated
Speaker 1: near thermal vents. Additionally, hemicyanin helps these tentacled critters regulate
Speaker 1: the salt content of their blood so that it matches
Speaker 1: that of the water that they're swimming. In next up brachiopods.
Speaker 1: These are ocean dwelling animals that resemble clams, though they
Speaker 1: evolved independently. Braccupods grow a pair of shells around the
Speaker 1: upper and lower surfaces of their squishy bodies, connected with
Speaker 1: a hinge at one end, a found in an assortment
Speaker 1: of marine habitats. The creatures filter tiny food particles out
Speaker 1: of the water. Although there are over three hundred living species,
Speaker 1: most people is so brachiopods with prehistoric times because these
Speaker 1: hard shelled creatures are disproportionately well represented in the fossil record.
Speaker 1: Extant brachiopods do not rely on either hemoglobin or hemocyanin
Speaker 1: to ferry oxygen in the blood. Instead, they have heemerthrine,
Speaker 1: yet another pigmented protein. Like hemoglobin, it contains iron atoms,
Speaker 1: albeit in a different arrangement. Heemerythrine makes deoxygenated blood look colorless,
Speaker 1: too faintly yellow. Once the blood starts taking on oxygen,
Speaker 1: it adopts a violet, pinkish hue. You'll also see this
Speaker 1: kind of blood in marine worms in the class Sypuncula.
Speaker 1: They're nicknamed peanut worms because some of them have bodies
Speaker 1: that grow in small pointed ovals, looking a bit like
Speaker 1: shelled peanuts. These buddies often reside in shallow waters, burrowing
Speaker 1: in sand or mud, or taking up in crevices or
Speaker 1: unoccupied shells. Other ocean going worms have a different circulatory setup.
Speaker 1: If a diver were to spot a live polyket cruising
Speaker 1: through the waves, they might mistake it for a sentient
Speaker 1: feather duster. Most of these worms are covered in bristles
Speaker 1: and tentacles, whose function varies from species to species. Some
Speaker 1: have red blood, but others harbor green blood. The latter
Speaker 1: use the oxygen binding protein chlorocrurine in place of hemoglobin.
Speaker 1: It also uses iron to bind to oxygen, but in
Speaker 1: yet another formation, it's what's called dichroic, or too colored,
Speaker 1: which means that it can appear to be different colors
Speaker 1: in different circumstances. When chlorocrurine is concentrated, its molecules stack
Speaker 1: to appear deep red brown, but when it's dilute it
Speaker 1: appears green, which means that even if Kermit was right,
Speaker 1: and it's not easy being green, at least those new
Speaker 1: guinea skinks have some creepy Crawley Company. Today's episode is
Speaker 1: based on the article Five Animals whose Blood Isn't read
Speaker 1: on HowStuffWorks dot Com, written by Mark Mancini. Brain Stuff
Speaker 1: is production of iHeartRadio in partnership with HowStuffWorks dot Com
Speaker 1: and is produced by Tyler Klang. Four more podcasts my
Speaker 1: heart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever
Speaker 1: you listen to your favorite shows.