WEBVTT - How Does Bioluminescence Work? 0:00:01.840 --> 0:00:07.800 Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff Lauren 0:00:07.840 --> 0:00:12.399 vogelbomb here. Animals that use their sense of sight to 0:00:12.520 --> 0:00:15.920 navigate generally have a hard time getting around without light, 0:00:16.400 --> 0:00:19.360 so there are a lot of adaptations out there to help. 0:00:20.720 --> 0:00:24.920 For example, owls have very large, tubular eyes that they 0:00:25.000 --> 0:00:27.960 use to collect a lot of light. Cats have a 0:00:28.040 --> 0:00:31.000 layer of highly reflective material deep in their eyes to 0:00:31.240 --> 0:00:33.879 give their light receptors a second chance at gathering it. 0:00:35.040 --> 0:00:37.959 Humans have put a lot of effort into creating portable, 0:00:38.159 --> 0:00:42.720 often artificial light sources, from torches to light bulbs and LEDs. 0:00:44.680 --> 0:00:49.319 Some bioluminescent life forms have an entirely different approach. They 0:00:49.360 --> 0:00:52.320 make their own light and carry it around in their bodies. 0:00:53.600 --> 0:00:56.360 Some of these animals use the light they produce the 0:00:56.360 --> 0:01:01.400 same way that people use flashlights or searchlights, but bioluminescent 0:01:01.400 --> 0:01:04.680 animals produce light very differently from the way that traditional 0:01:04.760 --> 0:01:09.639 light bulbs do. Traditional light bulbs and fires, for that matter, 0:01:10.160 --> 0:01:15.080 create light through incandescence. A material like wood or a 0:01:15.120 --> 0:01:19.039 filament inside a bulb gets very hot and emits light. 0:01:20.400 --> 0:01:24.520 This process isn't particularly efficient, since generating enough heat to 0:01:24.600 --> 0:01:28.800 create light wastes an enormous amount of energy. That's why 0:01:28.959 --> 0:01:32.119 led light bulbs have become so popular. They use what's 0:01:32.160 --> 0:01:36.640 called electroluminescence to basically use a low amount of electrical 0:01:36.680 --> 0:01:40.000 current to produce photons. When that current is run through 0:01:40.160 --> 0:01:45.160 certain semiconductive substances, it produces light but wastes a lot 0:01:45.240 --> 0:01:50.520 less energy. In life forms that use luminescence, chemical compounds 0:01:50.600 --> 0:01:54.240 mixed together to produce a glow. It's a lot like 0:01:54.280 --> 0:01:57.200 the way that substances inside a light stick combine to 0:01:57.240 --> 0:02:01.560 make light. Illuminescence of any kind is far more efficient 0:02:01.600 --> 0:02:05.720 than incandescence. It neither requires nor generates much heat, so 0:02:05.760 --> 0:02:10.560 it's sometimes known as cold light, hot or cold. A 0:02:10.680 --> 0:02:15.720 light generally comes from one source, an excited electron. Basically, 0:02:16.040 --> 0:02:18.800 energy causes an electron to move up a level in 0:02:18.840 --> 0:02:22.640 its atomic orbit. When the electron settles back down, it 0:02:22.720 --> 0:02:26.760 releases a photon, or a tiny packet of light. The 0:02:26.840 --> 0:02:30.040 result in various life forms can be beautiful alike the 0:02:30.120 --> 0:02:34.000 twinkling of fireflies, or a little eerie, like the glow 0:02:34.040 --> 0:02:37.800 of foxfire. It can have all kinds of uses, from 0:02:37.919 --> 0:02:43.320 protection to predation to we're not really sure what today, 0:02:43.560 --> 0:02:47.480 let's talk about the basic process behind bioluminescence and how 0:02:47.520 --> 0:02:52.000 different life forms use it to their advantage. You can 0:02:52.040 --> 0:02:56.560 find bioluminescent life forms all over our planet. On land. 0:02:56.760 --> 0:03:01.120 The aforementioned foxfire comes from glowing species of fungi that 0:03:01.160 --> 0:03:05.600 feed on rotting wood, creating an ectoplasm green carpet of 0:03:05.680 --> 0:03:09.919 light in Appalachian and other forests at night. In some 0:03:10.000 --> 0:03:13.800 types of fungus, the whole structure glows, in others only parts, 0:03:14.480 --> 0:03:19.079 like the aptly nicknamed jack o lantern, mushrooms, gills. Then 0:03:19.120 --> 0:03:23.440 there are various land animals, including some insects, centipedes, millipedes, 0:03:23.480 --> 0:03:27.720 and worms. You know fireflies and glowworms, which are the 0:03:27.800 --> 0:03:32.880 larvae of various species of flies and beetles. But most 0:03:32.919 --> 0:03:36.920 of the world's bioluminescence exists in the oceans, and particularly 0:03:36.960 --> 0:03:40.520 in the depths known as the twilight zone. This has 0:03:40.600 --> 0:03:43.200 nothing to do with rod sterling that I know of. 0:03:44.440 --> 0:03:47.160 In this zone, which extends from about six hundred and 0:03:47.160 --> 0:03:50.040 sixty to three thousand, three hundred feet which is two 0:03:50.120 --> 0:03:54.240 hundred to one thousand meters, some light but very little 0:03:54.600 --> 0:03:59.280 penetrates from the surface. The water above this zone absorbs 0:03:59.280 --> 0:04:03.640 wavelengths red, orange, and yellow sunlight and scatters violet light, 0:04:04.160 --> 0:04:07.200 so the light that reaches the twilight zone is bluish 0:04:07.200 --> 0:04:11.120 green in color. At this depth you can find lots 0:04:11.160 --> 0:04:17.080 of bioluminescent jellyfish, squid, shrimp, krill, marine worms, and fish. 0:04:17.560 --> 0:04:20.800 Most make light that matches that blue green sunlight that 0:04:20.880 --> 0:04:24.760 exists in this zone. The animal's glow can travel a 0:04:24.760 --> 0:04:27.279 long way and it can blend in with the light above. 0:04:28.480 --> 0:04:31.839 In some places, these animals, not the sun, are the 0:04:32.000 --> 0:04:38.839 primary source of light, So that's weird. Next question, why 0:04:40.680 --> 0:04:44.000 Hypothetically the evolution of something that requires a body to 0:04:44.120 --> 0:04:48.440 use precious resources usually has a reason. Like I said 0:04:48.440 --> 0:04:51.720 a minute ago, we don't know all of them yet. 0:04:52.120 --> 0:04:56.960 For example, several species of earthworm secrete luminescent stuff that 0:04:57.160 --> 0:05:02.080 doesn't have an obvious purpose. We think that some mushrooms 0:05:02.120 --> 0:05:05.320 glow to attract insects to help spread the mushrooms spores. 0:05:05.520 --> 0:05:09.760 But yeh, a few animals light up when nearby animals 0:05:09.800 --> 0:05:12.800 start to glow, and there's not always a clear reason 0:05:12.839 --> 0:05:16.400 for this behavior. One of my favorite examples is the 0:05:16.400 --> 0:05:20.000 phenomenon known as the milky sea Awhere in the surface 0:05:20.040 --> 0:05:24.520 of the ocean glows at night. Okay, so some species 0:05:24.560 --> 0:05:29.039 of single celled plankton glow when they're disturbed. Tides, storms, 0:05:29.160 --> 0:05:32.880 swimming marine life, and passing ships can cause large numbers 0:05:32.880 --> 0:05:37.600 of these plankton to produce light simultaneously. In some cases, 0:05:37.839 --> 0:05:41.440 this glow is so bright that it interferes with marine navigation. 0:05:42.880 --> 0:05:45.760 There's a hypothesis that this works sort of like a 0:05:45.760 --> 0:05:50.320 burglar alarm to help the population of plankton survive. The 0:05:50.400 --> 0:05:52.840 idea goes that if a small fish begins to feed 0:05:52.880 --> 0:05:56.080 on the plankton, the disturbed plankton emit a flash of light. 0:05:57.120 --> 0:06:00.320 The light attracts larger fish, which are likely to be 0:06:00.360 --> 0:06:03.400 the smaller fish as predators, and will thus prevent more 0:06:03.400 --> 0:06:08.839 of the plankton from being eaten by eating those smaller fish. However, 0:06:09.040 --> 0:06:11.680 this system doesn't seem to be as fool proof as 0:06:11.680 --> 0:06:16.919 some of the better understood uses for bioluminescence. So what 0:06:17.040 --> 0:06:21.240 do we know. We know that some animals use bioluminescence 0:06:21.279 --> 0:06:25.360 for communication. Of Fireflies flash at one another in species 0:06:25.400 --> 0:06:29.720 specific patterns, often in order to find a mate, but 0:06:29.839 --> 0:06:33.919 attraction isn't always benevolent. In the twilight depths, of the ocean. 0:06:34.040 --> 0:06:37.839 Some fish species, like the anglerfish, use aluminescent lure to 0:06:37.880 --> 0:06:43.040 attract prey. Some twilight zone fish species use their luminescence 0:06:43.160 --> 0:06:47.040 more like a spotlight to find prey. A one species 0:06:47.080 --> 0:06:51.600 of loose jawfish produces red wavelengths of light because red 0:06:51.640 --> 0:06:54.919 is uncommon at those depths, many deep water species didn't 0:06:54.960 --> 0:06:57.799 evolve to see it, so we think the loose jaws 0:06:57.839 --> 0:07:00.719 red light may allow it to spot and sneak up 0:07:00.760 --> 0:07:07.400 on prey. Bioluminescence can also be used for camouflage and mimicry. Okay, 0:07:07.720 --> 0:07:09.800 in the darker parts of the ocean, it's hard to 0:07:09.840 --> 0:07:13.160 see anything below you, but easy to see the silhouette 0:07:13.160 --> 0:07:17.040 of what's above you. For this reason, some species produce 0:07:17.120 --> 0:07:20.680 spots of light on their undersides, which blur their outlines 0:07:20.800 --> 0:07:23.000 and allow them to blend in with the light coming 0:07:23.000 --> 0:07:28.520 from above. This is also known as counter illumination. Or 0:07:28.840 --> 0:07:32.160 take for example, the cookie cutter shark, which has one 0:07:32.360 --> 0:07:36.000 unlit patch on its underside, and that patch resembles a 0:07:36.040 --> 0:07:40.080 smaller fish when viewed from below. Thus, a predator may 0:07:40.120 --> 0:07:42.640 approach and this shark can take a bite out of 0:07:42.640 --> 0:07:45.600 it and then flee which allows the cookie cutter shark 0:07:45.680 --> 0:07:48.480 to prey on animals that are much larger and more powerful. 0:07:49.960 --> 0:07:53.640 Bioluminescence can also be used for self defense when threatened. 0:07:53.760 --> 0:07:57.440 Some animals release a cloud of bioluminescent fluid, similar to 0:07:57.520 --> 0:08:00.000 the way that squid defend themselves with a cloud of anis. 0:08:01.400 --> 0:08:06.160 Others use a bright flash to temporarily blind predators. But 0:08:06.480 --> 0:08:10.560 okay I said earlier that bioluminescence comes from chemical reactions. 0:08:11.240 --> 0:08:13.760 For all of these different uses of light in all 0:08:13.800 --> 0:08:17.160 of these different organisms, the actual compounds at play can 0:08:17.240 --> 0:08:22.360 be different, but the basic formula is the same. In general, 0:08:22.480 --> 0:08:26.360 bioluminescence involves the combination of two types of substances in 0:08:26.440 --> 0:08:32.559 a light producing reaction, a luciferin and a luciferase. Luciferns 0:08:32.600 --> 0:08:36.760 are a category of light producing substances. Luciferases are a 0:08:36.800 --> 0:08:42.080 category of enzymes that catalyze the reaction. Often the process 0:08:42.080 --> 0:08:45.520 requires the presence of other substances, like oxygen or a 0:08:45.600 --> 0:08:49.880 denticine triphosphate that's ATP, a molecule that stores and transports 0:08:49.960 --> 0:08:55.280 energy in living cells. The luciferase basically allows the oxygen 0:08:55.400 --> 0:08:59.600 or whatever to interact with the dormant luciferin, thus prompting 0:08:59.640 --> 0:09:03.720 it to produce photons of light. The terms both come 0:09:03.760 --> 0:09:08.440 from the Latin term lucifer which means light bringer. Lots 0:09:08.440 --> 0:09:13.280 of different substances can act like luciferins and luciferases. For example, 0:09:13.480 --> 0:09:17.480 those milky seed plankton obtain their energy through photosynthesis, and 0:09:17.640 --> 0:09:21.839 they have a luciferin that resembles chlorophyll. Some shrimp and 0:09:21.920 --> 0:09:24.960 fish appear to manufacture their lucifern from the food that 0:09:25.000 --> 0:09:29.880 they eat, but not all bioluminescent life forms produce their 0:09:29.960 --> 0:09:34.360 own light. Some animals create these substances in their own bodies, 0:09:34.400 --> 0:09:39.640 but others have developed a symbiotic relationship with light producing bacteria. 0:09:40.520 --> 0:09:43.800 These bacteria typically live in a specialized organ in the 0:09:43.880 --> 0:09:48.560 host organism's body. The bacteria produce light all the time, 0:09:49.000 --> 0:09:51.480 so in order to turn their lights on and off, 0:09:51.840 --> 0:09:55.440 some animals can pull and push their light producing organs 0:09:55.559 --> 0:09:58.640 into and out of their bodies. Others cover them with 0:09:58.679 --> 0:10:03.160 membranes of skin to eyelids. Because of all of these 0:10:03.240 --> 0:10:07.640 variations and how bioluminescence works, researchers think that this ability 0:10:07.679 --> 0:10:11.640 to make light evolved independently in multiple forms of life, 0:10:12.840 --> 0:10:16.840 and although humans didn't evolve by iluminescence, we've been using 0:10:16.880 --> 0:10:21.280 it to our advantage for thousands of years. In ancient Rome, 0:10:21.480 --> 0:10:24.280 plenty of the Elder wrote about using jellyfish goo to 0:10:24.400 --> 0:10:27.760 paint a walking stick and making it into a cold torch. 0:10:29.080 --> 0:10:32.160 People around the world have picked foxfire fungi to use 0:10:32.200 --> 0:10:35.840 his lanterns, or cultivated them along pathways to light a trail. 0:10:37.080 --> 0:10:40.720 During World War Two, the Japanese army harvested and dried 0:10:40.920 --> 0:10:45.480 tiny bioluminescent crustaceans that, when crushed by soldiers in the field, 0:10:45.920 --> 0:10:49.800 provided just enough light to say, read a map, without 0:10:49.800 --> 0:10:54.760 giving their location away to any enemies nearby. Modern navies 0:10:54.920 --> 0:10:59.280 track milky seed plankton to detect enemy movement, and researchers 0:10:59.320 --> 0:11:03.880 can similarly track animals to learn more about them. Researchers 0:11:03.880 --> 0:11:07.880 have even used luciferins and luciferases to help tag and 0:11:08.240 --> 0:11:12.280 literally illuminate the workings of different cells and proteins in 0:11:12.400 --> 0:11:15.959 order to better understand things like nerve damage in Alzheimer's 0:11:15.960 --> 0:11:21.200 disease and the proliferation of cancers in living bodies. But 0:11:21.720 --> 0:11:25.320 as I've said, we don't even understand everything there is 0:11:25.360 --> 0:11:31.480 to know about these beautiful and useful biological processes. Hopefully 0:11:31.559 --> 0:11:34.720 future research will help light the way to even more 0:11:34.760 --> 0:11:43.640 applications a bioluminescence. Today's episode is based on the article 0:11:43.720 --> 0:11:47.040 how bioluminescence works on how stuffworks dot com, written by 0:11:47.080 --> 0:11:49.520 Tracy V. Wilson, who you may be familiar with from 0:11:49.559 --> 0:11:51.760 a little show called Stuff You Missed in History class. 0:11:52.520 --> 0:11:54.920 Brain Stuff is production of by Heart Radio in partnership 0:11:54.920 --> 0:11:57.520 with how Stuffworks dot Com and is produced by Tyler Klang. 0:11:58.160 --> 0:12:01.320 Four more podcasts my heart Radio, visit the iHeartRadio app, 0:12:01.480 --> 0:12:04.439 Apple Podcasts, or wherever you listen to your favorite shows.