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