0 00:00:11,000 --> 00:00:20,000 1 00:00:07,400 --> 00:00:09,320 As dusk gives way to twilight, 2 00:00:09,320 --> 00:00:12,760 the encroaching darkness is lit by life. 3 00:00:16,880 --> 00:00:23,000 These dancing lights around me are produced by fireflies - 4 00:00:23,000 --> 00:00:27,360 creatures that have the strange ability to produce light. 5 00:00:27,360 --> 00:00:29,120 They bioluminesce. 6 00:00:32,880 --> 00:00:35,560 And fireflies are not alone. 7 00:00:35,560 --> 00:00:38,240 Scientists are finding ever more strange and wonderful 8 00:00:38,240 --> 00:00:41,480 glowing life forms all around the world. 9 00:00:46,560 --> 00:00:49,480 Living light has always fascinated me. 10 00:00:49,480 --> 00:00:53,360 And the discovery of more and more luminous creatures raises more 11 00:00:53,360 --> 00:00:55,240 and more questions. 12 00:00:55,240 --> 00:00:59,720 Why? What is the light for? And how is it made? 13 00:01:02,400 --> 00:01:03,640 In recent years, 14 00:01:03,640 --> 00:01:07,000 scientists have begun to find answers to those questions. 15 00:01:07,000 --> 00:01:08,560 And in doing so, 16 00:01:08,560 --> 00:01:12,600 they've taken us into a world that is utterly unlike our own. 17 00:01:18,760 --> 00:01:22,840 However astonishing these images look, they are all real. 18 00:01:27,360 --> 00:01:31,200 With help from new cameras, one designed just for this film, 19 00:01:31,200 --> 00:01:33,920 we can reveal this extraordinary phenomenon 20 00:01:33,920 --> 00:01:35,880 as it has never been seen before. 21 00:01:53,840 --> 00:01:57,080 Bioluminescence holds many mysteries. 22 00:01:57,080 --> 00:02:01,480 But we do know that fireflies use it to attract the opposite sex. 23 00:02:15,960 --> 00:02:21,840 Each species has its own flash code and WE can join in the conversation. 24 00:02:28,600 --> 00:02:33,560 I'm going to use this rod to fish for fireflies. 25 00:02:34,800 --> 00:02:38,720 It's the actual rod used by the scientist who was the first 26 00:02:38,720 --> 00:02:42,360 to decipher the various call signs of fireflies. 27 00:02:42,360 --> 00:02:47,120 And there are 15 different species, at least, around here. 28 00:02:47,120 --> 00:02:49,480 Each with its own signal. 29 00:02:49,480 --> 00:02:54,200 Biologist Jim Lloyd used the rod to imitate male fireflies 30 00:02:54,200 --> 00:02:58,200 and so decode their various light patterns. 31 00:02:58,200 --> 00:03:02,720 He discovered that the call sign consisted partly in 32 00:03:02,720 --> 00:03:05,920 the actual flight path of the species concerned. 33 00:03:05,920 --> 00:03:08,080 There are, for example, 34 00:03:08,080 --> 00:03:12,360 some fireflies which move steadily horizontally, like that. 35 00:03:12,360 --> 00:03:14,760 And there are others which 36 00:03:14,760 --> 00:03:18,360 turn their light on as they climb, like that. 37 00:03:19,920 --> 00:03:24,840 But in addition to the flight path, they flash a particular signal. 38 00:03:24,840 --> 00:03:26,800 It's rather like Morse code. 39 00:03:27,920 --> 00:03:30,640 So I should be able to use this light myself. 40 00:03:32,440 --> 00:03:36,040 There is a female amongst these leaves here, 41 00:03:36,040 --> 00:03:38,880 which will emit a single flash. 42 00:03:38,880 --> 00:03:45,440 And the male of her species waits for precisely four seconds, 43 00:03:45,440 --> 00:03:48,560 and then answers back with a flash. 44 00:03:48,560 --> 00:03:53,160 Whereupon she immediately gives another flash, like that. 45 00:03:54,400 --> 00:03:58,440 And the male then knows that he is going to be a welcome visitor. 46 00:04:00,520 --> 00:04:03,560 But the message has recently been shown to be more than 47 00:04:03,560 --> 00:04:05,560 a simple signal for sex. 48 00:04:07,040 --> 00:04:10,320 A female judges the quality of a male's genes 49 00:04:10,320 --> 00:04:13,960 by the precision of his timing and the brightness of his light. 50 00:04:19,960 --> 00:04:24,680 She encourages her chosen suitor by directing her lanterns towards him. 51 00:04:35,960 --> 00:04:39,960 And it seems this male sent out all the right signals. 52 00:04:44,720 --> 00:04:46,360 We are now discovering that 53 00:04:46,360 --> 00:04:49,200 this language of light even has local dialects. 54 00:04:54,360 --> 00:04:58,040 Throughout the summer months, from Florida to southern Canada, 55 00:04:58,040 --> 00:05:02,600 gardens, fields and forests sparkle with these mating messages. 56 00:05:07,080 --> 00:05:09,120 Time-lapse photography reveals 57 00:05:09,120 --> 00:05:11,920 the extraordinary extent of this courtship. 58 00:05:17,880 --> 00:05:21,000 Some species flash only at dusk. 59 00:05:23,160 --> 00:05:26,320 Others prefer the forest canopy for their light show. 60 00:05:31,240 --> 00:05:35,680 Some species make their flashes more conspicuous by choosing 61 00:05:35,680 --> 00:05:38,280 the very darkest places in which to display. 62 00:05:39,320 --> 00:05:44,160 I can see virtually nothing here, except the flashes. 63 00:05:46,680 --> 00:05:50,040 And this particular species has another trick, too. 64 00:05:51,040 --> 00:05:53,760 It synchronises the displays. 65 00:05:53,760 --> 00:05:56,400 Individuals flash together. 66 00:06:00,840 --> 00:06:03,600 Each individual is triggered by its neighbour, 67 00:06:03,600 --> 00:06:07,600 and soon waves of light pulse through the woods. 68 00:06:13,960 --> 00:06:16,520 Speeded up, the wave becomes clearer. 69 00:06:25,520 --> 00:06:26,800 Between the waves, 70 00:06:26,800 --> 00:06:31,080 an impressed female can respond with two flashes of her own. 71 00:06:33,440 --> 00:06:35,080 And the males home in on her. 72 00:06:37,840 --> 00:06:39,760 But she can only choose one. 73 00:06:44,240 --> 00:06:48,360 These displays peak for just a few nights in June, 74 00:06:48,360 --> 00:06:52,160 which could explain why they were only recently discovered. 75 00:06:54,040 --> 00:06:57,680 Why they all flash together is still a mystery. 76 00:07:05,960 --> 00:07:10,080 It's surprising how little we know about bioluminescence. 77 00:07:11,440 --> 00:07:13,880 Fireflies are perhaps the best understood 78 00:07:13,880 --> 00:07:18,520 but some living light is still very perplexing indeed. 79 00:07:18,520 --> 00:07:22,720 With dawn, the sexual signals of the fireflies are drowned 80 00:07:22,720 --> 00:07:25,040 by the increasing flood of light. 81 00:07:25,040 --> 00:07:27,800 The flies take refuge in the undergrowth, 82 00:07:27,800 --> 00:07:31,560 away from the sharp-eyed predators of the day. 83 00:07:31,560 --> 00:07:33,040 But right now, 84 00:07:33,040 --> 00:07:37,680 light is being produced by life in the soil under my feet. 85 00:07:41,360 --> 00:07:46,000 The threads of certain fungi form a glowing underground network. 86 00:07:55,160 --> 00:07:59,560 But why would a fungus shine in the permanent darkness of the soil? 87 00:07:59,560 --> 00:08:01,560 We simply don't know. 88 00:08:03,560 --> 00:08:07,240 And for years, fungus bioluminescence, 89 00:08:07,240 --> 00:08:10,680 like much other living light, was written off as a beautiful 90 00:08:10,680 --> 00:08:13,480 by-product of evolution with no function. 91 00:08:16,640 --> 00:08:20,760 But some species only glow above ground and only at night, 92 00:08:20,760 --> 00:08:23,680 when their intense green light is very obvious. 93 00:08:28,400 --> 00:08:31,600 If it was just a biochemical accident then surely 94 00:08:31,600 --> 00:08:33,880 they would shine all the time. 95 00:08:33,880 --> 00:08:36,320 The glow certainly attracts insects 96 00:08:36,320 --> 00:08:39,960 and the theory is that these visitors spread the fungal spores. 97 00:08:52,840 --> 00:08:55,960 So here, too, just as with fireflies, 98 00:08:55,960 --> 00:08:58,760 we're learning new things all the time. 99 00:09:04,360 --> 00:09:08,200 But much living light remains a beautiful enigma. 100 00:09:11,200 --> 00:09:12,920 And throughout history, 101 00:09:12,920 --> 00:09:16,680 stories of bioluminescence were often thought to be pure fiction. 102 00:09:18,960 --> 00:09:23,960 In the 1870s, Jules Verne, the French science-fiction novelist, 103 00:09:23,960 --> 00:09:28,280 wrote this in his book, 20,000 Leagues Under The Sea. 104 00:09:29,800 --> 00:09:33,960 "At seven o'clock in the evening, our ship, half-immersed, 105 00:09:33,960 --> 00:09:37,120 "was sailing in a sea of milk. 106 00:09:37,120 --> 00:09:40,880 "At first sight, the ocean seemed lactified. 107 00:09:40,880 --> 00:09:44,720 "The whole sky seemed black by contrast with 108 00:09:44,720 --> 00:09:47,640 "the whiteness of the waters." 109 00:09:47,640 --> 00:09:50,240 Jules Verne may have based this story 110 00:09:50,240 --> 00:09:52,680 on a myth told to him by sailors. 111 00:09:52,680 --> 00:09:57,080 But in 1995, the captain of a British vessel wrote 112 00:09:57,080 --> 00:10:00,840 a real-life account in his ship's log. 113 00:10:00,840 --> 00:10:04,080 "At 18:00 hours on a clear moonless night, 114 00:10:04,080 --> 00:10:08,240 "while 150 miles east of the Somalian coast, 115 00:10:08,240 --> 00:10:11,880 "a whitish glow was observed on the horizon. 116 00:10:11,880 --> 00:10:16,920 "And after 15 minutes of steaming, the ship was completely surrounded 117 00:10:16,920 --> 00:10:23,160 "by a sea of milky white colour with a fairly uniform luminescence. 118 00:10:23,160 --> 00:10:26,200 "And it appeared as though the ship was sailing over 119 00:10:26,200 --> 00:10:30,240 "a field of snow or gliding over the clouds." 120 00:10:33,880 --> 00:10:36,640 Reports like this are rarer than the supposed sightings 121 00:10:36,640 --> 00:10:38,760 of the Loch Ness Monster. 122 00:10:38,760 --> 00:10:41,400 And there was no photographic evidence. 123 00:10:44,320 --> 00:10:48,400 Some scientists, including marine biologist Steven Haddock, 124 00:10:48,400 --> 00:10:52,200 were curious, and sought confirmation from above. 125 00:10:54,600 --> 00:10:57,560 We wondered if you could find one of these ship reports where 126 00:10:57,560 --> 00:11:00,360 they record sailing through one of these milky seas, 127 00:11:00,360 --> 00:11:03,440 and actually find the corresponding satellite data that cover 128 00:11:03,440 --> 00:11:06,240 that area at that same time. 129 00:11:06,240 --> 00:11:09,680 So we looked at the satellite from the ship report in 1995 130 00:11:09,680 --> 00:11:12,600 and it was somewhat of a eureka moment. 131 00:11:12,600 --> 00:11:15,680 We cleaned up the noisy sensor image from the camera, 132 00:11:15,680 --> 00:11:19,960 we mapped it onto the ship track, and this 300km feature 133 00:11:19,960 --> 00:11:24,320 emerged on the map matching exactly with what the ship had reported. 134 00:11:24,320 --> 00:11:27,240 So it was really an amazing moment. 135 00:11:27,240 --> 00:11:30,640 We were able to document the full extent of the milky sea over 136 00:11:30,640 --> 00:11:34,160 three successive nights as it rotated with the currents. 137 00:11:34,160 --> 00:11:38,040 So satellite images from the space age validated 138 00:11:38,040 --> 00:11:40,520 a piece of maritime folklore. 139 00:11:42,360 --> 00:11:45,080 On rare occasions, the oceans do glow. 140 00:11:48,240 --> 00:11:49,920 But what was causing a glow 141 00:11:49,920 --> 00:11:52,520 so bright that it could be seen from space? 142 00:11:54,280 --> 00:11:58,560 The answer can be found at the back of a neglected fridge. 143 00:12:04,600 --> 00:12:09,440 Left for a couple of days, this sea bream starts to glow. 144 00:12:18,520 --> 00:12:22,200 The fish itself has no light-producing ability. 145 00:12:23,520 --> 00:12:27,760 The glow is, in fact, produced by bacteria that are found 146 00:12:27,760 --> 00:12:31,920 in almost all seawater when they start to feed on decaying fish. 147 00:12:33,360 --> 00:12:37,480 On rare occasions when currents and temperatures cause a large bloom of 148 00:12:37,480 --> 00:12:42,840 algae in the ocean, these very same bacteria also feed on dying algae. 149 00:12:44,400 --> 00:12:46,880 Once they reach a critical concentration, 150 00:12:46,880 --> 00:12:50,000 their secretions trigger others to glow. 151 00:12:52,120 --> 00:12:54,880 They were glowing in such numbers that they can be 152 00:12:54,880 --> 00:12:56,960 detected by a satellite in orbit. 153 00:13:07,160 --> 00:13:10,760 Bacteria are among the most ancient forms of life, 154 00:13:10,760 --> 00:13:14,560 so they may have been the very first living things to glow. 155 00:13:14,560 --> 00:13:17,120 But why they did so is still debated. 156 00:13:18,520 --> 00:13:22,440 Today some animals have stolen the genes of the bacteria, 157 00:13:22,440 --> 00:13:24,840 and incorporated them into their own DNA. 158 00:13:26,320 --> 00:13:29,760 Others have simply kidnapped the bacteria themselves. 159 00:13:38,760 --> 00:13:41,160 These lights are made by captives, 160 00:13:41,160 --> 00:13:45,560 which are farmed in special organs below the eyes of flashlight fish. 161 00:13:55,040 --> 00:13:58,400 They have harnessed the bacterial glow for many purposes. 162 00:14:01,240 --> 00:14:05,720 We can only see them because our special cameras use infrared light. 163 00:14:07,360 --> 00:14:10,640 But to a predator, the fish look like this. 164 00:14:12,200 --> 00:14:15,840 A confusion of lights which makes it hard to pick a single target. 165 00:14:24,480 --> 00:14:28,200 Just before they change direction, the fish give a quick blink. 166 00:14:36,680 --> 00:14:38,960 These lights have other functions, too. 167 00:14:40,920 --> 00:14:44,080 They act as headlights to illuminate the sea floor 168 00:14:44,080 --> 00:14:46,000 as the fish search for food. 169 00:14:55,280 --> 00:14:59,440 They may even help a fish to flirt with the opposite sex. 170 00:15:06,840 --> 00:15:08,720 Unlike their captive bacteria, 171 00:15:08,720 --> 00:15:13,400 flashlight fish use living light for functions we now understand. 172 00:15:16,520 --> 00:15:19,160 But how is the light made? 173 00:15:19,160 --> 00:15:21,520 While it might appear magic, 174 00:15:21,520 --> 00:15:25,840 it's actually a straightforward chemical reaction that happens 175 00:15:25,840 --> 00:15:31,680 when a substance is mixed with a particular enzyme, like this. 176 00:15:37,000 --> 00:15:39,280 Hey, presto, light. 177 00:15:42,040 --> 00:15:46,600 The exact chemical formula varies according to the species. 178 00:15:46,600 --> 00:15:52,280 The reaction is very similar to that with which bacteria produce energy. 179 00:15:52,280 --> 00:15:56,160 Indeed, it could well be that the first luminescence was 180 00:15:56,160 --> 00:15:58,520 a by-product of that process. 181 00:15:59,840 --> 00:16:03,520 An evolutionary accident that has been co-opted by the fish to 182 00:16:03,520 --> 00:16:05,680 help them survive. 183 00:16:07,400 --> 00:16:10,680 The chemicals involved are quite harmless. 184 00:16:10,680 --> 00:16:14,680 In fact, you can actually buy a lollipop which, 185 00:16:14,680 --> 00:16:19,280 when you put it in hot water, glows. 186 00:16:20,440 --> 00:16:27,120 But to be truthful, I don't really find that very appetising. 187 00:16:27,120 --> 00:16:31,120 Perhaps, at the back of my mind, there's a memory of those 188 00:16:31,120 --> 00:16:34,640 bacteria on rotting fish, which tells me 189 00:16:34,640 --> 00:16:38,000 that things that glow aren't all that nice to eat. 190 00:16:40,640 --> 00:16:43,920 Bacteria may have been the first living lights, 191 00:16:43,920 --> 00:16:47,520 but then many other organisms also developed the ability. 192 00:16:48,920 --> 00:16:51,520 From jellyfish to fungi and insects, 193 00:16:51,520 --> 00:16:56,160 bioluminescence has evolved independently over 50 times, 194 00:16:56,160 --> 00:17:00,200 and is now produced by thousands of different species. 195 00:17:02,920 --> 00:17:05,720 And defence seems to be a common function. 196 00:17:11,360 --> 00:17:14,280 Millipedes are found across the globe. 197 00:17:14,280 --> 00:17:16,200 Many are active during the day, 198 00:17:16,200 --> 00:17:18,760 scuttling across the damp forest floor. 199 00:17:20,320 --> 00:17:24,960 They can do this with impunity, because they are deadly poisonous. 200 00:17:24,960 --> 00:17:28,160 Their bright colours are a clear message to predators - 201 00:17:28,160 --> 00:17:32,240 "Do not eat me. I am laced with cyanide." 202 00:17:39,560 --> 00:17:42,880 But what about millipedes that are active at night? 203 00:17:45,520 --> 00:17:49,640 They are no less toxic than those that are active during the day. 204 00:17:51,960 --> 00:17:56,720 But, of course, colours at night are no warning at all. 205 00:17:56,720 --> 00:18:00,120 Could it be that luminescence is a way 206 00:18:00,120 --> 00:18:03,720 of warning off night-time predators? 207 00:18:04,960 --> 00:18:07,920 These extraordinary millipedes are only found 208 00:18:07,920 --> 00:18:10,040 in the high mountains of California. 209 00:18:11,160 --> 00:18:14,440 Their bioluminescence has never been filmed before. 210 00:18:16,680 --> 00:18:20,680 They can't be sending signals to one another, because they're blind. 211 00:18:23,040 --> 00:18:26,360 Their living light evolved separately from bacteria, 212 00:18:26,360 --> 00:18:30,400 from a chemical process that helps millipedes conserve water 213 00:18:30,400 --> 00:18:32,600 in dry environments. 214 00:18:32,600 --> 00:18:35,840 But since the millipedes already contain cyanide, 215 00:18:35,840 --> 00:18:37,800 the light evolved a function. 216 00:18:39,960 --> 00:18:43,440 To my eyes, he doesn't look very bright. 217 00:18:43,440 --> 00:18:48,000 But my eyes are not the eyes of a night-time predator, 218 00:18:48,000 --> 00:18:51,200 or indeed of our specialist camera. 219 00:18:51,200 --> 00:18:53,240 And to both of them, 220 00:18:53,240 --> 00:18:57,200 this could look very bright indeed and be a real warning. 221 00:18:59,080 --> 00:19:02,200 When scientists made clay models of these millipedes, 222 00:19:02,200 --> 00:19:03,880 half of which glowed, 223 00:19:03,880 --> 00:19:08,000 nocturnal predators were more likely to attack those that didn't glow. 224 00:19:13,280 --> 00:19:16,680 This simple experiment produced a clear result. 225 00:19:16,680 --> 00:19:20,760 Living light can act as a warning. 226 00:19:23,800 --> 00:19:27,280 But proving the function of bioluminescence is not always 227 00:19:27,280 --> 00:19:30,480 so easy, as a recent discovery has shown. 228 00:19:35,480 --> 00:19:40,760 These, surely, are like creatures from science-fiction. 229 00:19:40,760 --> 00:19:43,400 Luminous earthworms. 230 00:19:43,400 --> 00:19:44,920 A few years ago, 231 00:19:44,920 --> 00:19:49,920 a lady living in the Loire Valley in central France went out during the 232 00:19:49,920 --> 00:19:54,240 evening to look for her dog which was digging a hole in the garden. 233 00:19:54,240 --> 00:19:59,200 And in the bottom of the hole, the soil was glowing. 234 00:19:59,200 --> 00:20:03,480 It was these earthworms. She could hardly believe her eyes. 235 00:20:03,480 --> 00:20:06,360 And she went and told people what she had seen 236 00:20:06,360 --> 00:20:08,280 and few people would believe her. 237 00:20:08,280 --> 00:20:12,360 The species of worm was already known, it lived over quite 238 00:20:12,360 --> 00:20:16,480 a lot of France, but no-one had ever seen it glow before. 239 00:20:16,480 --> 00:20:20,320 Perhaps that's because few people went out in the middle of the night 240 00:20:20,320 --> 00:20:23,400 digging a hole, especially without a light. 241 00:20:23,400 --> 00:20:27,880 But eventually, science recognised these creatures. 242 00:20:27,880 --> 00:20:32,160 But why should they luminesce in the darkness of the soil? 243 00:20:33,280 --> 00:20:35,440 Nobody knew. 244 00:20:38,520 --> 00:20:43,720 This blue light had gone unnoticed by science until 2010, 245 00:20:43,720 --> 00:20:48,200 when biologist Marcel Koken first saw their eerie glow. 246 00:20:50,880 --> 00:20:54,680 We are trying to find out why this animal produces light. 247 00:20:54,680 --> 00:20:58,360 A thing living underground. Why produce light? 248 00:20:58,360 --> 00:21:01,040 No use for it, apparently. 249 00:21:01,040 --> 00:21:04,960 Is it just a by-product of some internal chemistry? 250 00:21:04,960 --> 00:21:07,920 Or could the glow be used to frighten off attackers? 251 00:21:09,160 --> 00:21:13,560 These ground beetles are voracious predators and they love earthworms. 252 00:21:16,000 --> 00:21:19,560 The worms look like ordinary ones until the light goes out. 253 00:21:20,960 --> 00:21:22,680 Our special camera gives us 254 00:21:22,680 --> 00:21:25,600 a privileged view of what's happening in the dark. 255 00:21:30,840 --> 00:21:34,000 Marcel's experiments have shown that the worms can 256 00:21:34,000 --> 00:21:36,440 control their brightness. 257 00:21:36,440 --> 00:21:40,200 When the beetle touches part of the worm, its light gets brighter. 258 00:21:42,960 --> 00:21:46,400 So it could be that in case a predator tries to bite it, 259 00:21:46,400 --> 00:21:49,240 it lights up, that scares the predator. 260 00:21:49,240 --> 00:21:52,120 The predator goes off and the earthworm can escape. 261 00:21:53,400 --> 00:21:56,480 The beetle bites, and the worm's entire body 262 00:21:56,480 --> 00:21:59,400 bursts into light as it struggles to break free. 263 00:22:00,480 --> 00:22:03,160 But the beetle doesn't seem put off by the glow. 264 00:22:07,440 --> 00:22:10,680 If this is defence, it isn't working here. 265 00:22:12,480 --> 00:22:14,880 Marcel is still looking for the function. 266 00:22:17,000 --> 00:22:20,760 Perhaps other predators are put off or perhaps the worms use 267 00:22:20,760 --> 00:22:22,240 light to find each other. 268 00:22:26,240 --> 00:22:31,080 So it seems that this beautiful glow has a function which 269 00:22:31,080 --> 00:22:32,840 we still don't understand. 270 00:22:35,280 --> 00:22:39,320 The world of living light is full of mysteries. 271 00:22:39,320 --> 00:22:41,840 The French worms went unnoticed for so long 272 00:22:41,840 --> 00:22:45,200 because they produce their eerie light underground. 273 00:22:47,800 --> 00:22:49,400 But there are rare occasions 274 00:22:49,400 --> 00:22:52,920 when luminous life is all about revealing yourself. 275 00:23:02,400 --> 00:23:04,720 May 2015. 276 00:23:04,720 --> 00:23:08,360 While the southern aurora illuminates the night sky above, 277 00:23:08,360 --> 00:23:11,960 the sea below produces a strange blue glow. 278 00:23:21,400 --> 00:23:24,640 Each wave causes a ripple of intense colour. 279 00:23:38,080 --> 00:23:41,040 The animals in the bay notice it first. 280 00:23:43,200 --> 00:23:46,000 Wading birds are attracted to small crustaceans 281 00:23:46,000 --> 00:23:47,400 caught in the glow. 282 00:23:51,040 --> 00:23:54,600 Each movement alerts others to this rare spectacle. 283 00:23:54,600 --> 00:23:58,160 People gather to marvel at this once-in-a-lifetime event. 284 00:24:02,520 --> 00:24:03,920 That is amazing! 285 00:24:03,920 --> 00:24:06,960 I've never seen anything like this before in my life. 286 00:24:09,200 --> 00:24:10,240 That's wicked. 287 00:24:13,960 --> 00:24:17,480 LAUGHTER 288 00:24:24,560 --> 00:24:28,600 It may look like something from Willy Wonka's chocolate factory, 289 00:24:28,600 --> 00:24:30,480 but the phenomenon is real. 290 00:24:31,920 --> 00:24:35,960 A mass bloom of microscopic organisms caused by a rare 291 00:24:35,960 --> 00:24:39,560 combination of climate and nutrients. 292 00:24:39,560 --> 00:24:44,800 Under this microscope, I've got a drop of ordinary seawater. 293 00:24:44,800 --> 00:24:49,240 And it's full of tiny organisms, invisible to the naked eye, 294 00:24:49,240 --> 00:24:50,640 called dinoflagellates. 295 00:24:51,840 --> 00:24:54,760 And if I disturb them in some way, 296 00:24:54,760 --> 00:24:59,560 they combine two chemicals in their body to produce a flash of light. 297 00:24:59,560 --> 00:25:01,120 Watch. 298 00:25:17,880 --> 00:25:19,800 Dinoflagellates are one of the 299 00:25:19,800 --> 00:25:22,400 biggest single-celled organisms known. 300 00:25:24,240 --> 00:25:27,640 They are 1,000 times bigger than bacteria. 301 00:25:27,640 --> 00:25:29,600 They are neither animal nor plant, 302 00:25:29,600 --> 00:25:32,160 but have characteristics of them both, 303 00:25:32,160 --> 00:25:36,040 and when conditions are right in the sea, as they were in Tasmania, 304 00:25:36,040 --> 00:25:38,440 they bloom in enormous numbers. 305 00:25:41,560 --> 00:25:45,040 Bioluminescent tides like this one are certainly rare. 306 00:25:48,800 --> 00:25:53,920 However, dinoflagellates are found in huge numbers all over the world. 307 00:25:53,920 --> 00:25:58,480 They are among the most widespread of all bioluminescent life. 308 00:25:58,480 --> 00:26:00,040 Wherever they exist, 309 00:26:00,040 --> 00:26:04,120 these single-celled creatures highlight anything that moves. 310 00:26:07,800 --> 00:26:12,600 But why do dinoflagellates behave in this way? 311 00:26:12,600 --> 00:26:16,280 It's certainly not to entertain us, though it obviously does. 312 00:26:16,280 --> 00:26:19,240 Well, it could be that it is a kind of burglar alarm - 313 00:26:19,240 --> 00:26:22,360 that when a shrimp or some other animal 314 00:26:22,360 --> 00:26:25,440 that feeds on the dinoflagellates by filtering them out, 315 00:26:25,440 --> 00:26:27,560 comes along and starts to feed, 316 00:26:27,560 --> 00:26:30,360 it is, in doing so, illuminating itself. 317 00:26:33,800 --> 00:26:37,840 So that attracts the attention of perhaps bigger fish that might 318 00:26:37,840 --> 00:26:39,280 feed on the shrimp. 319 00:26:41,600 --> 00:26:45,600 Just as a flashing burglar alarm alerts the police to a thief, 320 00:26:45,600 --> 00:26:49,360 the dinoflagellates expose their attacker to its enemies. 321 00:26:54,680 --> 00:26:58,560 The shrimp is revealed to a cuttlefish, with fatal results. 322 00:27:02,840 --> 00:27:06,840 And so the cuttlefish can hunt in total darkness. 323 00:27:08,000 --> 00:27:11,600 But while the dinoflagellates' light can work in this way, 324 00:27:11,600 --> 00:27:14,360 it is still debated if that's why they do it. 325 00:27:18,000 --> 00:27:21,400 Whatever the reason, the magic created by their light can be 326 00:27:21,400 --> 00:27:24,240 one of nature's most magical spectacles. 327 00:27:40,920 --> 00:27:44,320 Bow-riding dolphins are revealed as dazzling outlines. 328 00:27:51,840 --> 00:27:56,120 Whenever these lights appear, the way life in the ocean hunts 329 00:27:56,120 --> 00:27:58,000 and hides is transformed. 330 00:27:59,120 --> 00:28:02,320 Perhaps dolphins are guided to their prey by the light 331 00:28:02,320 --> 00:28:03,760 of the dinoflagellates. 332 00:28:16,760 --> 00:28:21,640 Only now has it become possible to film these scenes with such clarity. 333 00:28:21,640 --> 00:28:25,600 But every night, spectacular light shows like this play out 334 00:28:25,600 --> 00:28:28,720 somewhere in the vastness of the oceans. 335 00:28:44,360 --> 00:28:48,720 While exactly how dinoflagellates use bioluminescence remains 336 00:28:48,720 --> 00:28:51,320 unproven, there are other instances 337 00:28:51,320 --> 00:28:55,400 when the burglar alarm effect has been clearly demonstrated. 338 00:29:03,320 --> 00:29:05,760 Caribbean coral reefs are some of the 339 00:29:05,760 --> 00:29:08,200 most well-dived waters in the world... 340 00:29:09,520 --> 00:29:10,560 ..by day. 341 00:29:22,320 --> 00:29:26,120 At night, it's a different world. 342 00:29:28,240 --> 00:29:31,320 A crab searches for a tasty morsel. 343 00:29:34,840 --> 00:29:37,560 This is just what it's looking for, the delicate 344 00:29:37,560 --> 00:29:41,200 tentacles of a brittle star, a relative of starfish. 345 00:29:52,040 --> 00:29:56,520 But the brittle star has a surprisingly effective defence. 346 00:29:59,160 --> 00:30:03,840 When disturbed, it unleashes a dazzling weapon, raising the alarm. 347 00:30:06,200 --> 00:30:09,000 Having been revealed, the crab makes a run for it. 348 00:30:15,200 --> 00:30:19,560 And the normally well camouflaged crustacean becomes easy prey 349 00:30:19,560 --> 00:30:22,120 for the octopus, even in the gloom. 350 00:30:24,520 --> 00:30:28,000 Scientists have only recently proved the light helps the 351 00:30:28,000 --> 00:30:32,400 brittle star drive off predators or, better still, to get them eaten. 352 00:30:39,320 --> 00:30:42,960 It's in the open water, where there's nowhere to hide, that the 353 00:30:42,960 --> 00:30:45,640 burglar alarm defence is most effective. 354 00:30:47,000 --> 00:30:51,160 Fish hunt small invertebrates silhouetted against the night sky. 355 00:30:53,200 --> 00:30:57,160 Ostracods, tiny crustaceans no bigger than a grain of sand, 356 00:30:57,160 --> 00:30:58,480 emerge from the reef. 357 00:31:00,880 --> 00:31:04,480 Cardinal fish are common predators of the small and unwary. 358 00:31:06,200 --> 00:31:08,440 But when they strike an ostracod, 359 00:31:08,440 --> 00:31:10,640 they get more than they bargained for. 360 00:31:13,080 --> 00:31:16,560 The ostracod discharges a bioluminescent flash bomb, 361 00:31:16,560 --> 00:31:19,160 one of the brightest forms of living light. 362 00:31:19,160 --> 00:31:21,800 And the cardinal fish quickly spits it out. 363 00:31:26,320 --> 00:31:29,240 The light is so bright that it shines through 364 00:31:29,240 --> 00:31:33,320 the body of the fish, temporarily blinding it, and this normally 365 00:31:33,320 --> 00:31:36,560 invisible fish becomes an easy target for a predator. 366 00:31:47,000 --> 00:31:49,720 Ostracods, with their flash bomb defence, 367 00:31:49,720 --> 00:31:52,000 are found throughout the world's oceans. 368 00:31:58,520 --> 00:32:00,240 But in the Caribbean, 369 00:32:00,240 --> 00:32:03,680 they employ their glow to attract as well as to repel. 370 00:32:06,960 --> 00:32:09,960 It's something that researchers Gretchen Gerrish 371 00:32:09,960 --> 00:32:11,920 and Trevor Rivers are studying. 372 00:32:11,920 --> 00:32:14,960 The spectacular mating display of ostracods. 373 00:32:16,600 --> 00:32:19,800 But they can't even begin to work until the moon has set. 374 00:32:21,320 --> 00:32:25,120 A fully moonlit night is not dark in the eyes of an organism that 375 00:32:25,120 --> 00:32:29,600 depends on their own light that they create, and so darkness truly 376 00:32:29,600 --> 00:32:34,080 is just a starlit sky, no moon present in the sky at all. 377 00:32:44,160 --> 00:32:47,880 Diving without torches in near total darkness, Gretchen 378 00:32:47,880 --> 00:32:51,960 and Trevor are entering a world that few people ever witness. 379 00:32:55,200 --> 00:32:58,440 You are immersed in darkness, you are immersed in water. 380 00:32:59,600 --> 00:33:03,000 And you see streaming stars floating past you and they're being 381 00:33:03,000 --> 00:33:07,080 produced by these tiny crustaceans that we barely understand. 382 00:33:08,480 --> 00:33:11,840 By releasing small amounts of glowing liquid as they swim, 383 00:33:11,840 --> 00:33:15,360 male ostracods leave a trail of lights in their wake. 384 00:33:17,000 --> 00:33:21,200 The series of precisely timed dots tell the female where 385 00:33:21,200 --> 00:33:23,520 he will be in exactly half a second. 386 00:33:25,960 --> 00:33:30,640 But as one male starts to display, another and another join him. 387 00:33:37,560 --> 00:33:38,960 And as they synchronise, 388 00:33:38,960 --> 00:33:42,960 they fan out into this firework-like display of light. 389 00:33:47,480 --> 00:33:50,760 It's one of the most awe-inspiring things I've ever seen. 390 00:34:01,240 --> 00:34:05,600 With every research trip, Trevor and Gretchen discover new species, 391 00:34:05,600 --> 00:34:08,560 each with its own light language. 392 00:34:23,200 --> 00:34:26,680 Ostracods and fireflies use bioluminescence 393 00:34:26,680 --> 00:34:28,600 to find potential mates. 394 00:34:28,600 --> 00:34:32,440 And it can be an efficient means of getting your message across, 395 00:34:32,440 --> 00:34:35,360 but it's not foolproof. 396 00:34:35,360 --> 00:34:37,600 Those messages can be hacked. 397 00:34:39,480 --> 00:34:42,920 There's a love cheat in this situation. 398 00:34:42,920 --> 00:34:47,880 There's also a female of a particular species here that, 399 00:34:47,880 --> 00:34:52,280 when she sees the males of a different species fly past, 400 00:34:52,280 --> 00:34:56,760 answers with their particular call sign, and that attracts them. 401 00:34:56,760 --> 00:35:00,760 And when they arrive, instead of mating with them, 402 00:35:00,760 --> 00:35:03,160 she has her own dastardly way with them. 403 00:35:06,160 --> 00:35:09,680 She mimics the flash patterns of other species. 404 00:35:13,680 --> 00:35:16,640 An unsuspecting male is lured in. 405 00:35:32,560 --> 00:35:37,960 Fireflies contain toxins thought to protect them against most predators. 406 00:35:37,960 --> 00:35:40,640 But this femme fatale is not put off. 407 00:35:42,840 --> 00:35:45,480 And she eats him alive. 408 00:35:45,480 --> 00:35:48,360 In fact, it may be the toxins that she is after. 409 00:35:50,200 --> 00:35:53,280 She can't produce such chemicals herself. 410 00:35:53,280 --> 00:35:59,040 So she tricks and then devours males of different species to obtain them. 411 00:36:04,040 --> 00:36:08,080 If she can't get males to come to her, she goes after them. 412 00:36:10,520 --> 00:36:14,640 And a good place to look for one is on a spider's web. 413 00:36:19,920 --> 00:36:22,040 A male firefly is ensnared. 414 00:36:22,040 --> 00:36:24,640 As the spider venom takes effect, 415 00:36:24,640 --> 00:36:27,360 his flashing turns to a constant glow. 416 00:36:34,080 --> 00:36:37,760 The femme fatale is alerted by the dim glow, 417 00:36:37,760 --> 00:36:42,240 and she flies straight onto the web to steal the spider's catch. 418 00:36:44,080 --> 00:36:46,400 As the spider struggles to keep its prey, 419 00:36:46,400 --> 00:36:48,680 she dazzles it with her lantern. 420 00:36:56,440 --> 00:36:59,960 Using her light, the firefly can clearly see the spider 421 00:36:59,960 --> 00:37:01,240 and avoid the web. 422 00:37:06,000 --> 00:37:08,920 The confused spider loses out. 423 00:37:16,840 --> 00:37:21,600 Predation turns out to be one area where light-making life 424 00:37:21,600 --> 00:37:23,520 has been very creative. 425 00:37:28,720 --> 00:37:31,440 Like a scene from the surface of an alien planet, 426 00:37:31,440 --> 00:37:35,400 these termite mounds have lodgers living in their walls. 427 00:37:43,480 --> 00:37:47,040 The luminous larvae of click beetles wait in burrows. 428 00:37:55,320 --> 00:37:59,040 Insects are drawn to their death by the green glow, 429 00:37:59,040 --> 00:38:00,760 like moths to a flame. 430 00:38:03,680 --> 00:38:05,880 And the beetle larvae gorge 431 00:38:05,880 --> 00:38:09,360 on the steady supply of unsuspecting victims. 432 00:38:19,560 --> 00:38:22,080 These predators work as individuals. 433 00:38:25,720 --> 00:38:29,240 There is another insect that excels in deception. 434 00:38:31,360 --> 00:38:34,600 But it works alongside thousands of its own kind. 435 00:38:38,000 --> 00:38:41,960 From outside, this cave shows no sign of the astonishing 436 00:38:41,960 --> 00:38:43,760 things that go on inside. 437 00:38:49,800 --> 00:38:53,280 The entrance is fringed with a curtain of silk, 438 00:38:53,280 --> 00:38:55,640 woven by the larvae of a kind of gnat. 439 00:38:57,560 --> 00:38:59,840 They move back and forth along the rocks, 440 00:38:59,840 --> 00:39:04,120 lowering sticky strings of saliva from the roof of the cave. 441 00:39:09,280 --> 00:39:11,280 As night falls, the walls 442 00:39:11,280 --> 00:39:15,880 and ceiling of this cavern become nature's very own planetarium. 443 00:39:26,240 --> 00:39:27,280 The trap is set. 444 00:39:30,560 --> 00:39:35,800 The cool, blue light produced in each larva's tail is the lure. 445 00:39:41,240 --> 00:39:42,680 Other insects that hatch 446 00:39:42,680 --> 00:39:47,800 and emerge in the cave instinctively fly upwards to the sky. 447 00:39:47,800 --> 00:39:51,760 But this is not a starlit sky. It's a deathtrap. 448 00:40:04,360 --> 00:40:07,640 Bioluminescence is clearly a powerful tool 449 00:40:07,640 --> 00:40:10,320 to these life forms that possess it. 450 00:40:10,320 --> 00:40:13,920 But it is only effective in darkness. 451 00:40:13,920 --> 00:40:15,120 Each dawn, 452 00:40:15,120 --> 00:40:19,120 the bright rays of the sun overwhelm the power of living light. 453 00:40:24,800 --> 00:40:27,520 For all of the wonders of bioluminescence 454 00:40:27,520 --> 00:40:30,760 in the plains and woodlands of the Earth, there is 455 00:40:30,760 --> 00:40:35,960 one place where living light is virtually the key to existence. 456 00:40:35,960 --> 00:40:39,680 The world of eternal darkness, the deep sea. 457 00:40:48,080 --> 00:40:51,640 The Western Fire is one of the world's most advanced 458 00:40:51,640 --> 00:40:53,600 deep sea research vessels. 459 00:40:55,400 --> 00:40:58,040 In the black depths there are no edges. 460 00:40:59,040 --> 00:41:01,680 No boundaries, nowhere to hide. 461 00:41:03,120 --> 00:41:06,200 Predators and prey have therefore had to develop some 462 00:41:06,200 --> 00:41:08,880 extraordinary strategies to stay alive. 463 00:41:08,880 --> 00:41:11,280 And many do so with the help of light. 464 00:41:13,600 --> 00:41:17,840 Dr Steven Haddock has spent the last 25 years studying the 465 00:41:17,840 --> 00:41:21,720 least known part of our planet, the ocean depths. 466 00:41:23,280 --> 00:41:26,360 I think people look at bioluminescence, 467 00:41:26,360 --> 00:41:30,640 this ability to make light, they think of it as a very magical thing, 468 00:41:30,640 --> 00:41:34,920 but once you see the diversity and the range of functions that 469 00:41:34,920 --> 00:41:37,640 bioluminescence serves for animals in the ocean, it is 470 00:41:37,640 --> 00:41:40,160 clear that it is a critical part of the whole ecology 471 00:41:40,160 --> 00:41:41,200 of the system. 472 00:41:41,200 --> 00:41:44,200 Until recently, it was all but impossible 473 00:41:44,200 --> 00:41:49,160 to collect living bioluminescent creatures from the deep. 474 00:41:49,160 --> 00:41:52,840 But this remote submersible, known as the Doc Ricketts, 475 00:41:52,840 --> 00:41:55,040 is equipped to do just that. 476 00:41:56,840 --> 00:41:58,840 They are trying to find new life 477 00:41:58,840 --> 00:42:02,960 and clues as to why light-making has evolved in so many forms. 478 00:42:11,320 --> 00:42:14,840 In the control room, thousands of metres above, Steve 479 00:42:14,840 --> 00:42:18,920 and the crew navigate past alien-like life forms. 480 00:42:18,920 --> 00:42:19,960 Nice. 481 00:42:22,080 --> 00:42:23,280 Wow. 482 00:42:23,280 --> 00:42:26,720 But in truth, it is us who are the aliens down here. 483 00:42:43,520 --> 00:42:46,600 Although very sophisticated, the Doc Ricketts' 484 00:42:46,600 --> 00:42:51,360 own remote cameras are not sensitive enough to record bioluminescence, 485 00:42:51,360 --> 00:42:54,840 so they use bright lights to find and film these creatures. 486 00:42:57,240 --> 00:43:00,440 To have any hope of observing their light-making powers, 487 00:43:00,440 --> 00:43:04,000 the research team needs to bring them to the surface. 488 00:43:05,440 --> 00:43:09,360 Gentle suction and remotely controlled canisters are used to 489 00:43:09,360 --> 00:43:12,120 delicately scoop up the rare sea creatures. 490 00:43:18,640 --> 00:43:19,760 Vampire squid. 491 00:43:26,880 --> 00:43:27,960 Yes! 492 00:43:29,480 --> 00:43:30,920 Viper fish. 493 00:43:34,440 --> 00:43:36,520 Perfect. 494 00:43:36,520 --> 00:43:38,160 Oh, look at that! 495 00:43:38,160 --> 00:43:39,840 And dragonfish. 496 00:43:42,160 --> 00:43:45,480 They don't just sound like something from a sailor's tale of 497 00:43:45,480 --> 00:43:48,680 fantasy monsters, they look like them, too. 498 00:43:51,160 --> 00:43:54,800 This is one of the few dragonfish that has ever been seen alive. 499 00:43:57,760 --> 00:44:01,960 And it's one of the even fewer that have been captured unharmed. 500 00:44:05,560 --> 00:44:09,120 - Yes! - Yay! - Oh, my gosh. 501 00:44:14,360 --> 00:44:17,240 Once they arrive on the ship, thousands of metres 502 00:44:17,240 --> 00:44:21,000 above their normal environment, there is no time to waste. 503 00:44:21,000 --> 00:44:24,240 The enormous pressure change is likely to cause any 504 00:44:24,240 --> 00:44:27,000 bioluminescence abilities to disappear. 505 00:44:30,280 --> 00:44:33,400 The race is on to try and observe those abilities 506 00:44:33,400 --> 00:44:35,480 and understand their functions. 507 00:44:39,680 --> 00:44:41,520 Wow. 508 00:44:48,120 --> 00:44:50,840 In some species, it seems to be defensive. 509 00:44:52,200 --> 00:44:56,240 Like the circling flashes of the Atolla jellyfish. 510 00:44:59,240 --> 00:45:03,280 Or the rippling light waves of the Beroe comb jelly. 511 00:45:14,360 --> 00:45:17,320 In other species, like this viper fish, 512 00:45:17,320 --> 00:45:21,360 light is used not only for defence, but to lure prey. 513 00:45:26,280 --> 00:45:31,040 These pyrosomes, colonies of minute translucent creatures, 514 00:45:31,040 --> 00:45:34,640 use light to communicate within the colony. 515 00:45:34,640 --> 00:45:39,040 The team's experiment shows that as one colony begins to glow, 516 00:45:39,040 --> 00:45:41,200 its neighbours light up in response. 517 00:45:43,840 --> 00:45:45,680 What could they be saying? 518 00:45:49,960 --> 00:45:53,400 Thanks to the delicate sampling methods of the Doc Ricketts, 519 00:45:53,400 --> 00:45:55,880 the team are able to observe a living 520 00:45:55,880 --> 00:46:00,200 and luminescing dragonfish, a sight few have ever witnessed. 521 00:46:03,400 --> 00:46:04,640 Whatever their function, 522 00:46:04,640 --> 00:46:08,480 one thing unites all these types of bioluminescence - 523 00:46:08,480 --> 00:46:10,360 their otherworldly beauty. 524 00:46:16,240 --> 00:46:20,640 And this beauty is the result of an evolutionary arms race 525 00:46:20,640 --> 00:46:24,640 where light is a weapon to blind or deceive. 526 00:46:27,600 --> 00:46:32,040 In response, some animals have evolved the most sophisticated 527 00:46:32,040 --> 00:46:35,000 and bizarre eyes on the planet. 528 00:46:38,320 --> 00:46:43,120 The rare barreleye fish has eyes that can only look upwards, 529 00:46:43,120 --> 00:46:46,040 through the top of its translucent head. 530 00:46:46,040 --> 00:46:47,560 Searching for prey above. 531 00:46:50,040 --> 00:46:51,240 It is so rare, 532 00:46:51,240 --> 00:46:54,520 catching even a glimpse of it alive is a huge achievement. 533 00:47:01,040 --> 00:47:04,640 And the same is true for the cock-eyed squid. 534 00:47:04,640 --> 00:47:08,800 It has one normal eye and one strange, upward-looking eye. 535 00:47:18,160 --> 00:47:22,040 At this depth, it is too dark for human eyes. 536 00:47:22,040 --> 00:47:24,520 But the faintest light from the surface, 537 00:47:24,520 --> 00:47:29,280 half a kilometre above, can just reach this twilight zone. 538 00:47:32,280 --> 00:47:35,720 Firefly squid normally live at these depths. 539 00:47:35,720 --> 00:47:38,480 To prevent themselves from being seen from below, 540 00:47:38,480 --> 00:47:43,120 they hide themselves with light. 541 00:47:43,120 --> 00:47:45,200 It's a strange paradox. 542 00:47:45,200 --> 00:47:48,880 In this dark world, light can be used for camouflage. 543 00:47:53,560 --> 00:47:57,520 At close range, the light-emitting cells, called photophores, 544 00:47:57,520 --> 00:47:59,120 are easy to see. 545 00:47:59,120 --> 00:48:02,560 But from a distance, they break up the outline of the squid 546 00:48:02,560 --> 00:48:04,640 and it merges with the background. 547 00:48:10,520 --> 00:48:13,720 It's an elegant solution used by many creatures 548 00:48:13,720 --> 00:48:16,440 when a silhouette can be a death sentence. 549 00:48:24,680 --> 00:48:27,880 In shallower waters, the colour of the light changes 550 00:48:27,880 --> 00:48:33,000 so the squid, as it gets closer to the surface, uses green photophores. 551 00:48:43,480 --> 00:48:46,440 The lives of firefly squid are short. 552 00:48:46,440 --> 00:48:48,320 When they are only a year old, 553 00:48:48,320 --> 00:48:52,640 mated females make their final journey, to the surface to spawn. 554 00:48:57,960 --> 00:49:01,600 But even in their final moments, they are both spectacular 555 00:49:01,600 --> 00:49:02,640 and valuable. 556 00:49:11,560 --> 00:49:13,160 All along the coast here, 557 00:49:13,160 --> 00:49:16,320 these squid, which die naturally after spawning, 558 00:49:16,320 --> 00:49:18,480 are gathered as a local delicacy. 559 00:49:20,760 --> 00:49:23,560 It's largely through this fishery that we know 560 00:49:23,560 --> 00:49:26,200 anything at all about the firefly squid. 561 00:49:28,400 --> 00:49:30,440 Like so many deep sea creatures, 562 00:49:30,440 --> 00:49:33,200 their daily lives are still virtually unknown. 563 00:49:34,560 --> 00:49:39,360 What we do know is that their world is dominated by bioluminescence. 564 00:49:43,040 --> 00:49:46,160 We've come a long way from watching fireflies 565 00:49:46,160 --> 00:49:49,640 in the woodlands of Pennsylvania. 566 00:49:49,640 --> 00:49:54,160 Organisms that produce light on land may be exceptional 567 00:49:54,160 --> 00:49:55,600 but in the sea, 568 00:49:55,600 --> 00:49:59,400 creatures that do so, like these comb jellies, 569 00:49:59,400 --> 00:50:01,920 are, in fact, the norm. 570 00:50:06,520 --> 00:50:09,080 In the oceans and on land, 571 00:50:09,080 --> 00:50:13,560 living creatures of many kinds have harnessed the power of light in 572 00:50:13,560 --> 00:50:20,120 extraordinary ways, to mate, to lie, even to hide under a cloak of light. 573 00:50:24,080 --> 00:50:27,200 Yet, with the latest cameras and technology, we are 574 00:50:27,200 --> 00:50:31,560 only beginning to understand the lives of luminous creatures. 575 00:50:34,440 --> 00:50:40,720 There remain many mysteries. But what a beautiful world they create. 576 00:50:42,120 --> 00:50:46,960 And what a beautiful world awaits the scientists of the future. 577 00:51:03,200 --> 00:51:06,080 During this programme, we've had to use cameras 578 00:51:06,080 --> 00:51:08,800 that are far more sensitive than our own eyes 579 00:51:08,800 --> 00:51:13,760 and about as sensitive as many of the animals that we are showing. 580 00:51:17,000 --> 00:51:20,760 The eye is one of evolution's greatest achievements. 581 00:51:20,760 --> 00:51:24,520 And nature has certainly devised some fiendishly complex 582 00:51:24,520 --> 00:51:26,760 and sensitive examples. 583 00:51:26,760 --> 00:51:30,840 Some of which are designed specifically to see bioluminescence. 584 00:51:34,920 --> 00:51:39,520 When we enter the dark, we barely notice bioluminescence. 585 00:51:39,520 --> 00:51:41,840 But after a few minutes, physiological changes 586 00:51:41,840 --> 00:51:46,280 take place in our eyes that enable us to see living light. 587 00:51:47,320 --> 00:51:49,880 Cameras have always struggled to replicate 588 00:51:49,880 --> 00:51:51,400 what the human eye can do, 589 00:51:51,400 --> 00:51:53,920 but with special low-light cameras, 590 00:51:53,920 --> 00:51:57,000 we can now record glowing light at least as well, 591 00:51:57,000 --> 00:52:00,240 and sometimes better, than we can see it ourselves. 592 00:52:02,000 --> 00:52:06,400 But being able to film the glow is only one part of the solution. 593 00:52:06,400 --> 00:52:10,280 To really understand light on Earth, you need to be able to record 594 00:52:10,280 --> 00:52:13,080 the creature themselves as they make the light. 595 00:52:14,720 --> 00:52:16,880 This camera allows you to film 596 00:52:16,880 --> 00:52:20,040 in low-light levels in a completely new way. 597 00:52:20,040 --> 00:52:23,160 The beam of light comes in through the single lens, 598 00:52:23,160 --> 00:52:28,680 but it is then split into two, and one camera records on one 599 00:52:28,680 --> 00:52:33,960 light frequency, and the other on a different light frequency. 600 00:52:33,960 --> 00:52:37,920 One of the cameras is sensitive to infrared light, invisible to 601 00:52:37,920 --> 00:52:41,720 most animals, but which allows the camera to record in the dark. 602 00:52:42,760 --> 00:52:46,280 The second camera records only the bioluminescence, 603 00:52:46,280 --> 00:52:48,280 which is mostly blue or green. 604 00:52:49,480 --> 00:52:52,280 The two are then combined into one picture. 605 00:52:56,000 --> 00:52:59,520 And that way you can get pictures at a low-light level, 606 00:52:59,520 --> 00:53:01,960 not only of bioluminescent animals, 607 00:53:01,960 --> 00:53:05,160 but even the environment in which they are living. 608 00:53:05,160 --> 00:53:08,720 This technique, pioneered by film-maker Martin Dohrn, 609 00:53:08,720 --> 00:53:12,880 allows us to enter the world of bioluminescent creatures, 610 00:53:12,880 --> 00:53:16,280 and also to contribute to new science. 611 00:53:16,280 --> 00:53:18,400 With this type of camera, there are many things 612 00:53:18,400 --> 00:53:22,720 I see on these images which I wouldn't be able to see normally. 613 00:53:24,240 --> 00:53:28,200 In the past, scientist Marcel Koken has been unable to 614 00:53:28,200 --> 00:53:31,840 study the worm and beetle without using a light. 615 00:53:31,840 --> 00:53:34,560 But when he did, the light would frighten the beetle 616 00:53:34,560 --> 00:53:37,680 and overpower the worm's bioluminescence. 617 00:53:37,680 --> 00:53:41,560 With the help of Martin's camera, Marcel is able to observe 618 00:53:41,560 --> 00:53:46,240 and record the beetle and worm encounter for the first time. 619 00:53:46,240 --> 00:53:49,920 Having decided working with two cameras simultaneously wasn't 620 00:53:49,920 --> 00:53:54,800 already hard enough, the team decide to take them underwater. 621 00:53:54,800 --> 00:53:56,840 The objective was to film 622 00:53:56,840 --> 00:54:00,520 the beautiful mating display of ostracods - 623 00:54:00,520 --> 00:54:04,680 tiny, one millimetre long crustaceans in the dark 624 00:54:04,680 --> 00:54:09,760 swirling currents of their natural habitat. A huge challenge. 625 00:54:09,760 --> 00:54:12,840 - Martin, how was it tonight? - We had a lot of problems. 626 00:54:12,840 --> 00:54:16,800 Tonight, it went smoother. It's calmer. Much, much calmer. 627 00:54:16,800 --> 00:54:20,160 A lot of what I saw looked utterly amazing. 628 00:54:22,280 --> 00:54:25,760 Martin's beam-splitting system makes it possible to film 629 00:54:25,760 --> 00:54:29,560 the bioluminescence as well as the tiny ostracods, as they leave 630 00:54:29,560 --> 00:54:31,240 lights in their wake. 631 00:54:31,240 --> 00:54:34,200 However, the scientists are not done. 632 00:54:35,880 --> 00:54:39,880 Marine biologist Gretchen Gerrish hopes the camera will enable 633 00:54:39,880 --> 00:54:42,760 her to film groups of males that aren't flashing, 634 00:54:42,760 --> 00:54:45,800 swimming alongside the individual that is. 635 00:54:45,800 --> 00:54:48,800 Something that has only ever been seen in the lab. 636 00:54:51,360 --> 00:54:55,360 These males, known as sneakers, are invisible to a normal camera, 637 00:54:55,360 --> 00:54:57,800 because they leave no night trail. 638 00:54:57,800 --> 00:55:02,720 But our camera, nicknamed Bertha, could change all that. 639 00:55:02,720 --> 00:55:05,840 - So, how was Bertha? - Bertha is awesome. 640 00:55:05,840 --> 00:55:10,960 She was filming sneakers and you could see them swimming. 641 00:55:10,960 --> 00:55:13,200 She's a bit of a beast. 642 00:55:13,200 --> 00:55:16,240 What do you think, Trevor? Did you get any good footage? 643 00:55:16,240 --> 00:55:17,720 It was just awesome. 644 00:55:17,720 --> 00:55:19,840 This is opening the doors for so much. 645 00:55:21,040 --> 00:55:24,560 The scientists are keen to get their first look at the combined 646 00:55:24,560 --> 00:55:26,160 images from Bertha. 647 00:55:31,240 --> 00:55:34,880 The infrared does show there is a spiralling group of males, 648 00:55:34,880 --> 00:55:38,600 intent on intercepting the female, before she can reach the male 649 00:55:38,600 --> 00:55:41,400 that has done all the hard work of attracting her. 650 00:55:45,560 --> 00:55:47,680 And there are far more competing males 651 00:55:47,680 --> 00:55:50,120 than the scientists had expected. 652 00:55:51,120 --> 00:55:53,800 It's an ostracod soup. There's thousands of them. 653 00:55:54,800 --> 00:55:59,120 What, to our eyes, is a beautiful, orderly display is in fact 654 00:55:59,120 --> 00:56:01,160 an ostracod free-for-all. 655 00:56:01,160 --> 00:56:04,840 Lots of males try to cash in on the efforts of a few. 656 00:56:04,840 --> 00:56:07,560 The amount of information you could fire from this is something 657 00:56:07,560 --> 00:56:09,880 we've been trying to do for the last five years. 658 00:56:09,880 --> 00:56:11,360 Yeah, that's a paper, right there. 659 00:56:11,360 --> 00:56:13,920 What? You mean in that short clip? There's not a paper there. 660 00:56:13,920 --> 00:56:16,560 Close to it. 661 00:56:16,560 --> 00:56:20,160 But having hi-tech kit is only part of the story. 662 00:56:20,160 --> 00:56:22,960 Since much of the bioluminescence is little-known, 663 00:56:22,960 --> 00:56:26,840 just finding it is often the biggest hurdle. 664 00:56:26,840 --> 00:56:31,160 The crew are about to head out on their most ambitious shoot. 665 00:56:31,160 --> 00:56:32,600 Tonight, we're going to try 666 00:56:32,600 --> 00:56:35,920 and film something that we know is found all over the world, 667 00:56:35,920 --> 00:56:39,720 and it happens every night in every ocean, almost anywhere, 668 00:56:39,720 --> 00:56:43,120 and yet, in terms of getting information from people 669 00:56:43,120 --> 00:56:44,680 as to where we might find it, 670 00:56:44,680 --> 00:56:47,200 and when the best time is, there is nothing. 671 00:56:49,880 --> 00:56:54,880 As night falls, they head away from shore and any artificial light. 672 00:56:56,040 --> 00:56:59,840 And soon, they are sailing in the sea laced with dinoflagellates. 673 00:57:01,640 --> 00:57:03,720 These blue flashes can be seen 674 00:57:03,720 --> 00:57:07,080 in almost any ocean at night, with the lights out. 675 00:57:07,080 --> 00:57:10,080 But this alone is not what the crew came for. 676 00:57:10,080 --> 00:57:12,800 They are hoping to meet some special visitors. 677 00:57:23,320 --> 00:57:26,240 Working on a rocking boat in complete darkness with 678 00:57:26,240 --> 00:57:29,800 a prototype camera is one of the trickiest challenges Martin 679 00:57:29,800 --> 00:57:31,600 has faced in his career. 680 00:57:34,720 --> 00:57:38,840 After a week searching the dark sea, here they are. 681 00:57:38,840 --> 00:57:40,000 Dolphins. 682 00:57:48,720 --> 00:57:52,600 To be out at night, with clear skies and beautiful stars, 683 00:57:52,600 --> 00:57:56,000 and everywhere there are flashes of light, 684 00:57:56,000 --> 00:58:00,760 and when dolphins turn up, the show just gets more extraordinary still. 685 00:58:00,760 --> 00:58:04,600 It really is one of the most amazing things I've ever seen in my life. 686 00:58:06,480 --> 00:58:10,280 Scenes like this are happening across the oceans, 687 00:58:10,280 --> 00:58:14,040 yet this is one of the few times they've ever been caught on camera. 688 00:58:17,960 --> 00:58:21,200 New technologies and new ideas are creating 689 00:58:21,200 --> 00:58:25,080 a revolution in our way of seeing the world. 690 00:58:25,080 --> 00:58:28,120 And of understanding life that glows.