Speaker 1: Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff Lauren
Speaker 1: vogelbomb here. Animals that use their sense of sight to
Speaker 1: navigate generally have a hard time getting around without light,
Speaker 1: so there are a lot of adaptations out there to help.
Speaker 1: For example, owls have very large, tubular eyes that they
Speaker 1: use to collect a lot of light. Cats have a
Speaker 1: layer of highly reflective material deep in their eyes to
Speaker 1: give their light receptors a second chance at gathering it.
Speaker 1: Humans have put a lot of effort into creating portable,
Speaker 1: often artificial light sources, from torches to light bulbs and LEDs.
Speaker 1: Some bioluminescent life forms have an entirely different approach. They
Speaker 1: make their own light and carry it around in their bodies.
Speaker 1: Some of these animals use the light they produce the
Speaker 1: same way that people use flashlights or searchlights, but bioluminescent
Speaker 1: animals produce light very differently from the way that traditional
Speaker 1: light bulbs do. Traditional light bulbs and fires, for that matter,
Speaker 1: create light through incandescence. A material like wood or a
Speaker 1: filament inside a bulb gets very hot and emits light.
Speaker 1: This process isn't particularly efficient, since generating enough heat to
Speaker 1: create light wastes an enormous amount of energy. That's why
Speaker 1: led light bulbs have become so popular. They use what's
Speaker 1: called electroluminescence to basically use a low amount of electrical
Speaker 1: current to produce photons. When that current is run through
Speaker 1: certain semiconductive substances, it produces light but wastes a lot
Speaker 1: less energy. In life forms that use luminescence, chemical compounds
Speaker 1: mixed together to produce a glow. It's a lot like
Speaker 1: the way that substances inside a light stick combine to
Speaker 1: make light. Illuminescence of any kind is far more efficient
Speaker 1: than incandescence. It neither requires nor generates much heat, so
Speaker 1: it's sometimes known as cold light, hot or cold. A
Speaker 1: light generally comes from one source, an excited electron. Basically,
Speaker 1: energy causes an electron to move up a level in
Speaker 1: its atomic orbit. When the electron settles back down, it
Speaker 1: releases a photon, or a tiny packet of light. The
Speaker 1: result in various life forms can be beautiful alike the
Speaker 1: twinkling of fireflies, or a little eerie, like the glow
Speaker 1: of foxfire. It can have all kinds of uses, from
Speaker 1: protection to predation to we're not really sure what today,
Speaker 1: let's talk about the basic process behind bioluminescence and how
Speaker 1: different life forms use it to their advantage. You can
Speaker 1: find bioluminescent life forms all over our planet. On land.
Speaker 1: The aforementioned foxfire comes from glowing species of fungi that
Speaker 1: feed on rotting wood, creating an ectoplasm green carpet of
Speaker 1: light in Appalachian and other forests at night. In some
Speaker 1: types of fungus, the whole structure glows, in others only parts,
Speaker 1: like the aptly nicknamed jack o lantern, mushrooms, gills. Then
Speaker 1: there are various land animals, including some insects, centipedes, millipedes,
Speaker 1: and worms. You know fireflies and glowworms, which are the
Speaker 1: larvae of various species of flies and beetles. But most
Speaker 1: of the world's bioluminescence exists in the oceans, and particularly
Speaker 1: in the depths known as the twilight zone. This has
Speaker 1: nothing to do with rod sterling that I know of.
Speaker 1: In this zone, which extends from about six hundred and
Speaker 1: sixty to three thousand, three hundred feet which is two
Speaker 1: hundred to one thousand meters, some light but very little
Speaker 1: penetrates from the surface. The water above this zone absorbs
Speaker 1: wavelengths red, orange, and yellow sunlight and scatters violet light,
Speaker 1: so the light that reaches the twilight zone is bluish
Speaker 1: green in color. At this depth you can find lots
Speaker 1: of bioluminescent jellyfish, squid, shrimp, krill, marine worms, and fish.
Speaker 1: Most make light that matches that blue green sunlight that
Speaker 1: exists in this zone. The animal's glow can travel a
Speaker 1: long way and it can blend in with the light above.
Speaker 1: In some places, these animals, not the sun, are the
Speaker 1: primary source of light, So that's weird. Next question, why
Speaker 1: Hypothetically the evolution of something that requires a body to
Speaker 1: use precious resources usually has a reason. Like I said
Speaker 1: a minute ago, we don't know all of them yet.
Speaker 1: For example, several species of earthworm secrete luminescent stuff that
Speaker 1: doesn't have an obvious purpose. We think that some mushrooms
Speaker 1: glow to attract insects to help spread the mushrooms spores.
Speaker 1: But yeh, a few animals light up when nearby animals
Speaker 1: start to glow, and there's not always a clear reason
Speaker 1: for this behavior. One of my favorite examples is the
Speaker 1: phenomenon known as the milky sea Awhere in the surface
Speaker 1: of the ocean glows at night. Okay, so some species
Speaker 1: of single celled plankton glow when they're disturbed. Tides, storms,
Speaker 1: swimming marine life, and passing ships can cause large numbers
Speaker 1: of these plankton to produce light simultaneously. In some cases,
Speaker 1: this glow is so bright that it interferes with marine navigation.
Speaker 1: There's a hypothesis that this works sort of like a
Speaker 1: burglar alarm to help the population of plankton survive. The
Speaker 1: idea goes that if a small fish begins to feed
Speaker 1: on the plankton, the disturbed plankton emit a flash of light.
Speaker 1: The light attracts larger fish, which are likely to be
Speaker 1: the smaller fish as predators, and will thus prevent more
Speaker 1: of the plankton from being eaten by eating those smaller fish. However,
Speaker 1: this system doesn't seem to be as fool proof as
Speaker 1: some of the better understood uses for bioluminescence. So what
Speaker 1: do we know. We know that some animals use bioluminescence
Speaker 1: for communication. Of Fireflies flash at one another in species
Speaker 1: specific patterns, often in order to find a mate, but
Speaker 1: attraction isn't always benevolent. In the twilight depths, of the ocean.
Speaker 1: Some fish species, like the anglerfish, use aluminescent lure to
Speaker 1: attract prey. Some twilight zone fish species use their luminescence
Speaker 1: more like a spotlight to find prey. A one species
Speaker 1: of loose jawfish produces red wavelengths of light because red
Speaker 1: is uncommon at those depths, many deep water species didn't
Speaker 1: evolve to see it, so we think the loose jaws
Speaker 1: red light may allow it to spot and sneak up
Speaker 1: on prey. Bioluminescence can also be used for camouflage and mimicry. Okay,
Speaker 1: in the darker parts of the ocean, it's hard to
Speaker 1: see anything below you, but easy to see the silhouette
Speaker 1: of what's above you. For this reason, some species produce
Speaker 1: spots of light on their undersides, which blur their outlines
Speaker 1: and allow them to blend in with the light coming
Speaker 1: from above. This is also known as counter illumination. Or
Speaker 1: take for example, the cookie cutter shark, which has one
Speaker 1: unlit patch on its underside, and that patch resembles a
Speaker 1: smaller fish when viewed from below. Thus, a predator may
Speaker 1: approach and this shark can take a bite out of
Speaker 1: it and then flee which allows the cookie cutter shark
Speaker 1: to prey on animals that are much larger and more powerful.
Speaker 1: Bioluminescence can also be used for self defense when threatened.
Speaker 1: Some animals release a cloud of bioluminescent fluid, similar to
Speaker 1: the way that squid defend themselves with a cloud of anis.
Speaker 1: Others use a bright flash to temporarily blind predators. But
Speaker 1: okay I said earlier that bioluminescence comes from chemical reactions.
Speaker 1: For all of these different uses of light in all
Speaker 1: of these different organisms, the actual compounds at play can
Speaker 1: be different, but the basic formula is the same. In general,
Speaker 1: bioluminescence involves the combination of two types of substances in
Speaker 1: a light producing reaction, a luciferin and a luciferase. Luciferns
Speaker 1: are a category of light producing substances. Luciferases are a
Speaker 1: category of enzymes that catalyze the reaction. Often the process
Speaker 1: requires the presence of other substances, like oxygen or a
Speaker 1: denticine triphosphate that's ATP, a molecule that stores and transports
Speaker 1: energy in living cells. The luciferase basically allows the oxygen
Speaker 1: or whatever to interact with the dormant luciferin, thus prompting
Speaker 1: it to produce photons of light. The terms both come
Speaker 1: from the Latin term lucifer which means light bringer. Lots
Speaker 1: of different substances can act like luciferins and luciferases. For example,
Speaker 1: those milky seed plankton obtain their energy through photosynthesis, and
Speaker 1: they have a luciferin that resembles chlorophyll. Some shrimp and
Speaker 1: fish appear to manufacture their lucifern from the food that
Speaker 1: they eat, but not all bioluminescent life forms produce their
Speaker 1: own light. Some animals create these substances in their own bodies,
Speaker 1: but others have developed a symbiotic relationship with light producing bacteria.
Speaker 1: These bacteria typically live in a specialized organ in the
Speaker 1: host organism's body. The bacteria produce light all the time,
Speaker 1: so in order to turn their lights on and off,
Speaker 1: some animals can pull and push their light producing organs
Speaker 1: into and out of their bodies. Others cover them with
Speaker 1: membranes of skin to eyelids. Because of all of these
Speaker 1: variations and how bioluminescence works, researchers think that this ability
Speaker 1: to make light evolved independently in multiple forms of life,
Speaker 1: and although humans didn't evolve by iluminescence, we've been using
Speaker 1: it to our advantage for thousands of years. In ancient Rome,
Speaker 1: plenty of the Elder wrote about using jellyfish goo to
Speaker 1: paint a walking stick and making it into a cold torch.
Speaker 1: People around the world have picked foxfire fungi to use
Speaker 1: his lanterns, or cultivated them along pathways to light a trail.
Speaker 1: During World War Two, the Japanese army harvested and dried
Speaker 1: tiny bioluminescent crustaceans that, when crushed by soldiers in the field,
Speaker 1: provided just enough light to say, read a map, without
Speaker 1: giving their location away to any enemies nearby. Modern navies
Speaker 1: track milky seed plankton to detect enemy movement, and researchers
Speaker 1: can similarly track animals to learn more about them. Researchers
Speaker 1: have even used luciferins and luciferases to help tag and
Speaker 1: literally illuminate the workings of different cells and proteins in
Speaker 1: order to better understand things like nerve damage in Alzheimer's
Speaker 1: disease and the proliferation of cancers in living bodies. But
Speaker 1: as I've said, we don't even understand everything there is
Speaker 1: to know about these beautiful and useful biological processes. Hopefully
Speaker 1: future research will help light the way to even more
Speaker 1: applications a bioluminescence. Today's episode is based on the article
Speaker 1: how bioluminescence works on how stuffworks dot com, written by
Speaker 1: Tracy V. Wilson, who you may be familiar with from
Speaker 1: a little show called Stuff You Missed in History class.
Speaker 1: Brain Stuff is production of by Heart Radio in partnership
Speaker 1: with how Stuffworks dot Com and is produced by Tyler Klang.
Speaker 1: Four more podcasts my heart Radio, visit the iHeartRadio app,
Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.