WEBVTT Kind: captions Language: en 00:00:20.550 --> 00:00:25.510 As we travel from the surface of the ocean down through the water column, the amount 00:00:25.510 --> 00:00:28.530 of light available decreases with depth. 00:00:28.530 --> 00:00:35.160 Very little light from the surface penetrates between 200 and 1,000 meters, in what’s 00:00:35.160 --> 00:00:39.420 known as the twilight zone. 00:00:39.420 --> 00:00:45.300 And once we reach about 1,000 meters depth, light from above has disappeared entirely. 00:00:45.300 --> 00:00:51.370 But throughout the open ocean -- even in its darkest depths -- we encounter a different 00:00:51.370 --> 00:00:57.020 kind of light. 00:00:57.020 --> 00:01:02.949 The displays you see here are examples of bioluminescence, an adaptation that scientists 00:01:02.949 --> 00:01:12.580 estimate is found in more than 75% of the animals that live in the water column. 00:01:12.580 --> 00:01:17.950 Bioluminescence is a form of chemiluminescence, which is the production of visible light by 00:01:17.950 --> 00:01:20.720 a chemical reaction. 00:01:20.720 --> 00:01:28.440 Scientists call the process “bioluminescence” when the reaction occurs within a living organism. 00:01:28.440 --> 00:01:34.370 While relatively rare on land, bioluminescence is quite common throughout the open ocean 00:01:34.370 --> 00:01:41.650 -- particularly among fishes, jellies, squids, tunicates, and crustaceans. 00:01:41.650 --> 00:01:47.190 Along the coast you might even see the work of bioluminescent dinoflagellates -- tiny 00:01:47.190 --> 00:01:52.320 planktonic organisms -- that can cause the sea -- to glow. 00:01:52.320 --> 00:01:57.910 To tell us more about how bioluminescence is used by marine organisms and what questions 00:01:57.910 --> 00:02:02.340 keep scientists up at night, let's talk to an expert. 00:02:02.340 --> 00:02:03.590 Welcome Rene! 00:02:03.590 --> 00:02:09.600 Before we delve into the topic of bioluminescence, can you first tell us a bit more about yourself? 00:02:09.600 --> 00:02:11.410 Yeah, of course. 00:02:11.410 --> 00:02:17.450 So I'm a PhD student at the University of Kansas and I work here in the natural history 00:02:17.450 --> 00:02:18.450 museum. 00:02:18.450 --> 00:02:25.500 My research primarily focuses on the evolution of deep-sea fishes and I focus on a group 00:02:25.500 --> 00:02:27.280 called the lantern fishes. 00:02:27.280 --> 00:02:31.340 So where in the ocean do we most frequently see bioluminescence occurring? 00:02:31.340 --> 00:02:36.570 The majority of bioluminescence and where it occurs in the ocean, um, actually happens 00:02:36.570 --> 00:02:39.650 a lot in what we consider the open ocean mid-water zone. 00:02:39.650 --> 00:02:45.600 So these zones, um, specifically are called the Mesopelagic or the Twilight zone, and 00:02:45.600 --> 00:02:48.810 the bathypelagic called the midnight zone. 00:02:48.810 --> 00:02:53.030 And I actually looked this up recently and 4,000 meters is basically the entire length 00:02:53.030 --> 00:02:54.940 of central park in New York city. 00:02:54.940 --> 00:03:00.070 And so if you just, like, stood central park on its head and then went all the way down, 00:03:00.070 --> 00:03:01.760 that's approximately 4,000 meters. 00:03:01.760 --> 00:03:07.020 And it's just, it's kind of crazy to think about how much open space there is down there 00:03:07.020 --> 00:03:09.870 and how much water there is down there. 00:03:09.870 --> 00:03:14.930 And it's also important to note that many of these organisms aren't restricted to just 00:03:14.930 --> 00:03:15.930 one depth in the ocean. 00:03:15.930 --> 00:03:18.130 This is a three-dimensional world. 00:03:18.130 --> 00:03:23.490 And so many of them perform something called a daily vertical migration, where they swim 00:03:23.490 --> 00:03:28.000 up into the surface at night to feed on a bunch of the zooplankton and other organisms 00:03:28.000 --> 00:03:30.410 that survive and are very abundant up there. 00:03:30.410 --> 00:03:33.750 And then they swim back down into the deep sea during the day. 00:03:33.750 --> 00:03:36.190 And that's usually to hide from predators. 00:03:36.190 --> 00:03:41.740 And this mass migration is thought to be the largest migration on earth because it is constantly 00:03:41.740 --> 00:03:44.650 happening around the globe as we're rotating. 00:03:44.650 --> 00:03:48.900 Can you tell us what are some of the reasons why these animals actually bioluminesce? 00:03:48.900 --> 00:03:54.120 So if you're an organism that lives in the deep sea, one of the major benefits of evolving 00:03:54.120 --> 00:03:58.430 bioluminescence is to use it for a type of camouflage. 00:03:58.430 --> 00:04:03.980 Many of the organisms that live in this area have something called photophores or light 00:04:03.980 --> 00:04:06.209 organs on their stomachs. 00:04:06.209 --> 00:04:11.500 And much of the light that's produced by these stomach light organs specifically matches 00:04:11.500 --> 00:04:16.519 both the color and the intensity of light that's coming from the surface of the ocean. 00:04:16.519 --> 00:04:20.860 So this type of camouflage that they're doing is called counter illumination. 00:04:20.860 --> 00:04:23.430 Uh, some of the other cool behaviors or some of the things that bioluminescence is used 00:04:23.430 --> 00:04:24.810 for, if you think of an angler fish. 00:04:24.810 --> 00:04:30.410 So the one from finding nemo that has the esca on its head, uh, they use those to attract 00:04:30.410 --> 00:04:32.660 prey. 00:04:32.660 --> 00:04:35.820 It's also known to be used for defense mechanisms. 00:04:35.820 --> 00:04:43.430 So some species and some organisms will actually shoot out bioluminescent goo to make bright 00:04:43.430 --> 00:04:48.740 flashes to distract or stun different types of predators. 00:04:48.740 --> 00:04:53.650 And also living in the deep sea, it means you’ve got to get creative in order to communicate. 00:04:53.650 --> 00:04:59.789 And so many of the organisms that use bioluminescence use it, to communicate with each other. 00:04:59.789 --> 00:05:05.409 Can you explain how bioluminescence is actually produced by animals? 00:05:05.409 --> 00:05:07.939 In the simplest sense? 00:05:07.939 --> 00:05:13.879 Bioluminescence is actually created as a byproduct of a chemical reaction between the molecules 00:05:13.879 --> 00:05:16.900 luciferin and luciferase. 00:05:16.900 --> 00:05:21.659 Luciferin is called a substrate molecule, and it's the molecule that emits light. 00:05:21.659 --> 00:05:27.720 And this happens when it's combined with a luciferase, which is an enzyme and oxygen. 00:05:27.720 --> 00:05:32.169 So light along with oxyluciferin byproducts of that reaction. 00:05:32.169 --> 00:05:36.689 Alexandra Purit...: 23:22 Is the chemical reaction for bioluminescence the same for 00:05:36.689 --> 00:05:38.029 every species? 00:05:38.029 --> 00:05:42.460 Luciferase and luciferase are general terms. 00:05:42.460 --> 00:05:46.750 And there's actually a range of structures that fill the roles of each of these. 00:05:46.750 --> 00:05:49.180 And the fact that we see so many different kinds of luciferins and luciferases hints 00:05:49.180 --> 00:05:52.979 that the evolution of this trait didn't just happen once. 00:05:52.979 --> 00:05:58.520 Recent studies actually have shown that bioluminescence has evolved at least 94 different times across 00:05:58.520 --> 00:05:59.729 the tree of life. 00:05:59.729 --> 00:06:04.650 It's an insane number and it's actually a number that will probably increase as we identify 00:06:04.650 --> 00:06:10.520 new species and find new organisms, especially since the deep sea is one of the least explored 00:06:10.520 --> 00:06:12.860 areas on earth. 00:06:12.860 --> 00:06:17.780 So I'm curious to know what are some of the things that scientists are still uncertain 00:06:17.780 --> 00:06:22.259 about with regards to bioluminescence, and also to hear a little bit more about some 00:06:22.259 --> 00:06:25.340 of the current areas of research in this field? 00:06:25.340 --> 00:06:31.469 Yeah, of course -- we still don't actually know how many times bioluminescence has evolved 00:06:31.469 --> 00:06:37.069 or how many species are bioluminescent. 94 is just like our current hypothesis based 00:06:37.069 --> 00:06:39.210 on information that we have. 00:06:39.210 --> 00:06:44.930 We're constantly also finding those new chemical compounds of luciferin and luciferase, new 00:06:44.930 --> 00:06:51.430 light organ structures, new species that can bioluminesce, um, not only that, but we continue 00:06:51.430 --> 00:06:57.550 to find new ways that bioluminescence is used, different types of cells that can do it. 00:06:57.550 --> 00:07:03.919 And we still actually don't know much about how organisms store luciferins in their bodies. 00:07:03.919 --> 00:07:09.129 And so there's actually ongoing research in basically every single one of these areas. 00:07:09.129 --> 00:07:11.580 Rene, thank you so much for joining us today. 00:07:11.580 --> 00:07:12.659 It was really great speaking with you and learning more about the fascinating topic 00:07:12.659 --> 00:07:13.659 of bioluminescence. 00:07:13.659 --> 00:07:21.439 I hope I was able to bring light to some of the topics of bioluminescence. 00:07:21.439 --> 00:07:30.469 It's clear that in this dark and open environment, a little bit of light can go a long way. 00:07:30.469 --> 00:07:36.900 One of nature's most amazing phenomena, there's still a lot we don't know about bioluminescence, 00:07:36.900 --> 00:07:40.349 particularly in deep-sea organisms. 00:07:40.349 --> 00:07:47.849 The answers to our scientific mysteries begin with curiosity: What questions spark your 00:07:47.849 --> 00:07:50.189 curiosity about bioluminescence?