00:00Like this one.
00:04ROV Sebastian, a robot owned and operated by Schmidt Ocean Institute.
00:11It is the size of a small car.
00:18And depth rated to four and a half kilometers,
00:22its range covers the entirety of the Midnight Zone.
00:30Controlled from the surface vessel via a tether, Sebastian shines a light on the deep
00:40and reveals a glimpse at the veiled expanse beneath the ocean surface.
00:45As the ROV descends into the Midnight Zone, we begin to encounter obscurities unlike anything observed near the surface.
01:06Some are so small that they are barely visible to the naked eye.
01:20And others are giants.
01:29This is a place of pure darkness.
01:32Too deep for any light at all to penetrate.
01:34It's a harsh environment, where the large physical distance from the plankton that form the base of food webs limits the abundance of animals that the Midnight Zone can support.
01:45Life here must find a way to function in a cold, dark abyss, where temperatures do not exceed four degrees Celsius,
01:58and withstand extreme hydrostatic pressure that ranges from 100 atmospheres at the top of the zone to 400 at the bottom.
02:06In spite of these challenges, animals must make compromises and push their morphology and physiologies to the extreme,
02:17in order to avoid predators, find food, and locate mates amidst a massive pitch-black void.
02:24And so, a set of surreal adaptations are employed.
02:37Soft bodies, like that of the Cuskeel, can withstand the crushing pressures that would damage or kill most other creatures.
02:45Metabolisms are slowed dramatically.
02:56Time ticks to a slower tune here.
03:01It's the patient and the slow that grow old.
03:05Greenland sharks, belonging to the sleeper shark family, are known to live for centuries, 2,200 metres down in the cold depths of the Arctic Ocean,
03:21and growing longer than great whites, up to 7 metres.
03:24Like many animals down here, they exhibit a phenomenon called deep-sea gigantism,
03:35the tendency of deep-sea creatures to grow to sizes far exceeding those of their shallow water counterparts.
03:45Predators belong to a trophic niche you'd expect to be unsustainable in a place like this,
03:50where food is scarce enough already for the detritivores.
03:55So, to conserve energy, predators adopt sit-and-wait tactics, using the dark to their advantage.
04:04A comb jelly casts a net of tentacles lined not with stinging cells, but sticky collar blasts,
04:20that capture prey like a spider's web.
04:50Instead of feeding them, they produce the correct, they produce a Essie.
04:54They cause a lot of things to save, and become safe in spreading air.
04:55A lot of things to have been crucified...
04:56Until they have been damaged, they produce light once they finally get back to their own stock.
04:57After all, the objects to go to the bleachers have been damaged after a certain time.
05:00When they do not look too high, they are still in the negative way.
05:02Strips of fine hair-like cilia run the length of the body,
05:06and are beat synchronously, allowing the jelly to swim,
05:10and refracting light in shimmering waves.
05:15They also produce light of their own from special cells called photocytes.
05:20Bioluminescence, perhaps as a means of lowering prey.
05:33A lubate comb jelly lacks sticky tentacles.
05:38It uses its cilia to create a feeding current, engulfing prey.
05:50While in the twilight zone, bioluminescence is used to hide.
06:04Here, it instead gives a voice to the lonely wanderers of this midnight world.
06:09A female anglerfish wields a lure called an esca, filled with bioluminescent bacteria,
06:22and poised at the tip of a modified dorsal fin ray called an elysium.
06:28Encounters between anglerfishes happen so rarely that many have gone to extreme lengths to maximise their reproductive success.
06:36They exhibit exceptional sexual dimorphism.
06:42The males display no esca, and are dwarfed in size by the females.
06:47Yet possess large eyes and nostrils that allow them to detect the species-specific pheromones of the female.
06:53And once he finds her, a male will develop a pincer-like pair of denticles in his jaw, and latch on permanently to the female's body.
07:06Their circulatory systems combine, and the male reduces to nothing more than a shrivelled, sperm-producing sac, nourished and sustained by the female's blood.
07:17Efficiency is key in the ocean, and every aspect of an organism's anatomy and behaviour is optimised to solve the challenges they face.
07:30Body shapes make a world of difference, depending on the environment they inhabit.
07:36In the sunlit waters of the high seas, predatory fish spend most of their lives on the hunt.
07:56Water is 800 times more dense and 50 times more viscous than air, making it a challenge to move through.
08:07For a predator, it helps to be streamlined, with a rigid forked tail like that of the tuna.
08:13This is a fusiform body type.
08:17It minimises inertial drag and allows tuna to migrate more than 15,000 kilometres in a year, at times reaching 43 miles per hour.
08:33Fishes of the reef are compressed.
08:36They require agility, not speed, and so are flattened side to side for quick accurate turns, and darting among coral and rock.
08:50On the sandy sea floor, fish are flattened, with depressiform bodies.
09:00On the sandy sea floor, fish are flattened, with the sea floor, with the sea floor, with the sea floor, with the sea floor.
09:14But what about here, in the ocean's midnight void?
09:18Food is too scarce to support streamlined predators.
09:22There is no rock to dart among for cover, nor any floor for miles.
09:30There are two body types that seem to dominate.
09:36Rounded globiform fish, like anglers, are suited not for sustained swimming, but floating in weight of prey to come within reach.
09:45Others, like the sawtooth eel, are elongate and flexible.
10:02Anguilliform.
10:05This form not only allows it to conceal its silhouette by hanging vertically when it ventures into twilight waters,
10:19but enables it to move in a series of sinuous waves that pass along the body,
10:25and produce propulsive thrust for efficient swimming.
10:28The snipe eel moves in a similar way, but is thinner and more thread-shaped, with a body type known as phyloform.
10:46The jaws of its bird-like beak curve away from each other at their tips,
10:52covered with tiny, hooked, backward-pointing teeth for trapping minute crustaceans like shrimp,
10:58as it sweeps through the water, permanently agape.
11:01The snipe eel also boasts the most vertebrae of any animal on Earth, with more than 700 along its metre and a half long body.
11:14As fishes like these move, flexible throughout their entire length,
11:28the undulatory wave passes backward with increasing amplitude and speed,
11:33producing the highest propulsive thrust in the tail.
11:38It offers the most efficient method of locomotion in a place so starved of energy,
11:59without compromising on speed as the anglers have.
12:01Not being restricted to sit and wait tactics unlocks an assortment of feeding behaviours for anguiliform fishes.
12:14Like the oversized mouth of the gulper eel, it is larger than the rest of the body,
12:20and can be opened wide enough to scoop up shoals of shrimp or swallow animals much larger than itself.
12:26A pouch-like lower jaw holds the prey, while its stomach distends within to accommodate and digest the feast.
12:37There is a clear trend too in the colour of fishes here compared to the twilight zone.
12:44The shimmering silvery fishes are fewer, and instead a host of dark brown or black fishes prevail.
12:56Many boast an adaptation called ultra-blackness, with a surface covered in melanosomes containing extraordinarily high concentrations of the pigment melanin,
13:08that reflects, in some instances, less than half a percent of the light that falls upon them.
13:17It's in stark contrast to the reflective guanine crystals that allow silvering in fishes of the twilight zone,
13:23where being so dark would only make their silhouettes stand out in the sun's residual glow.
13:31Down here, it's a superpower.
13:35Light organs, located beneath each eye of this shiny loose-jawed dragonfish,
13:42produce red bioluminescence that serves as a searchlight.
13:45Pray that a bright red in colour, which typically appear black down here, stick out like a sore thumb in the red glow.
14:00The black-bellied dragonfish forgoes ultra-blackness in favour of brassy bronze skin,
14:05using a bioluminescent barbell on its chin that acts like an angler's lure.
14:09The large, backward-facing teeth of the toothy viperfish are too large to fit inside its mouth,
14:26but they act like a cage, ensuring prey can't escape once captured.
14:41Its fangs are formed from crystal nanostructures so small that wavelengths of light pass through instead of scattering,
14:48rendering them invisible to prey.
14:58Adorning the undersides of dragonfishes are bioluminescent dots used for counter-illumination,
15:05matching any light above when seen from below.
15:08The Pacific black-gin, Scopolengis tristis, has only been filmed in its natural environment a small number of times.
15:27In many of these encounters, it remains motionless, perhaps to avoid being seen.
15:37Like the bronze dragonfish, its silvery scales only shine when illuminated by the lights of an underwater robot,
15:45but in the dark may scatter light and obscure the shape of the body.
15:49Very little is known about their life history, like many fishes that hail from such depths.
16:02Chimera is one of the oldest fish in the ocean.
16:07An ancient relative of sharks that diverged from a common ancestor 200 million years ago.
16:14Running along its entire length is a lateral line system resembling patchwork for sensing movements in nearby water.
16:24For every 10 meters we descend, pressure increases by one atmosphere.
16:30To survive, fish have evolved strengthened protein structures and more fluid cellular membranes that preserve their vital biological functions.
16:38For others, including many cephalopods, a soft gelatinous body is all they need to overcome the pressure and maintain neutral buoyancy.
16:52Water cannot be compressed, so being composed primarily of water helps out down here.
17:01The dumbo octopus flaps a pair of enlarged ear-like mantle fins to move gracefully,
17:11steering with webbed arms as it traverses the void.
17:16Reaching depths of 6,000 meters, it is the deepest living octopus of all.
17:28Pressure at the lower end of its range can be 600 times greater than at sea level, equivalent to the weight of 50 jumbo jets.
17:39Although, to us, the conditions of the deep appear extreme, the features that define a challenging environment are always relative.
17:47For many of the residents down here, the ocean's surface is an extreme environment, and the low-pressure conditions of the shallows would prove lethal.
17:57Of the deep's eclectic tapestry of animals, the cephalopods are perhaps the most enigmatic.
18:14Displaying physiological, morphological, and behavioral modifications to become masters of this world.
18:24Each of them ethereal dancers, pushing the boundaries of adaptation to sculpt an existence uniquely their own.
18:31They dominate in a range of forms, displaying unusual appendages for feeding.
19:00The long, sticky feeding tentacles of the whiplash squid, Mastagopsis, are draped like flypaper into the water below, termed the tuning fork position, as it basks in a cloud of its own ink.
19:24Cutting out of its ink.
19:25dasher
19:28out of its own ink.
20:01When it's time to move on, the tentacles are retracted into membranous sheaths within the squid's arms.
20:31When it's time to move on, it's time to move on.
21:00The large eye of the strawberry squid allows it to spy the silhouettes of animals above against the deep blues of the twilight zone.
21:08By day, it resides at the very bottom of this zone, at around a thousand meters down, where a backdrop of fading light transitions to pitch black.
21:36It positions itself by turning or ratcheting its body, so that a second, smaller eye peers down into darkness, looking for luminous prey.
22:18It's time to move on.
22:20It's time to move on.
22:22It's time to move on.
22:24It's time to move on.
22:30It's time to move on.
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23:34Now, let's journey back down into the depths.
23:43The boundaries of the ocean zones are not clear-cut.
23:46The twilight and midnight regions both belong to the aphotic zone, defined as the depths beyond which less than 1% of sunlight penetrates.
23:57A place often referred to as the dark ocean.
24:01While some animals are adapted to either the twilight zone, tailored to a place where light is diminished but not absent,
24:09or the midnight zone, swallowed by pitch black, others are able to span both.
24:16In such cases, it helps to be born with an invisibility cloak.
24:23Aside from the eyes, optic nerves and a long, narrow digestive system, this glass octopus is almost entirely see-through.
24:39This one is a male.
24:47The small, hook-like tip of one tentacle is a modified sexual organ called the hectococculus, used to pass sperm to the female.
24:58A mature female.
24:59A mature female, reaching around 45 centimetres.
25:13A mature female, reaching around 45 centimetres.
25:26Her body is speckled with colour-producing cells called chromatophores that she uses for camouflage.
25:45Small muscles can expand to pull open the pigment sacks, darkening her body.
25:58It's the same mechanism behind the colour-changing abilities of many other cephalopods, laid bare by a transparent body.
26:10In the midnight zone, the feeding behaviours of squids and octopuses differs greatly from those of twilight animals.
26:23Above, in the mesopelagic, life is fast-paced, owing to the higher abundance of prey.
26:31Squids here hunt in groups, swarming and inking to confuse scores of fish.
26:46Among the largest to do so, are the Humboldt squid.
27:01Launching tentacles lined with barbed suckers to grab silvery lanternfish.
27:05Fğaziope.
27:06Nasa помàssara.
27:07And in the short of the sea.
27:08Magnet panicking.
27:09Unsungest in the fundamental taken by cloak-dropping, coming to the sea.
27:10Fough, the final dark of the sea.
27:11In the dark of the sea.
27:12To the sky is a very strong, a safe day.
27:13For a very good day.
27:14Keep in contact with ships.
27:15And in the dark of the sea.
27:16In the dark of the sea.
27:18In the dark of the sea.
27:19Rang smokers.
27:20He's a beautiful man.
27:21To the sky is a special secret.
27:22He's a beautiful man.
27:23That's a beautiful man for the world.
27:24In the dark of the sea.
27:25The Amaury of the sea.
27:27That's 100% anything.
27:28Oh man.
27:29You see the sun.
27:30Scenes like this are a nightly occurrence in the Twilight Zone,
27:46initiated by the slightest changes in ambient light as the sun sets,
27:50calling forth great swarms of twilight fish
27:53that gather to migrate vertically under the cover of darkness.
27:57This phenomenon is one of the only reasons why large active hunters like Humboldt squid
28:05are able to sustain such an energetic lifestyle.
28:18In the bathypelagic, you must be opportunistic to succeed.
28:23Schooling fish are few, but sinking organic debris is plentiful.
28:32Marine snow.
28:34The scraps left over from the feasts above.
28:36In a velvet cloak, the vampire squid dangles a long filamentous tentacle,
28:51covered in adhesive mucus, to trap these fine particles.
28:54It is well-suited to a place starved of not just food, but oxygen.
29:08Its blood contains a respiratory pigment, hemocyanin,
29:12that has the highest affinity for oxygen of any known cephalopod.
29:16Thus, the vampire squid can reduce competition from other detritivores
29:21by occupying the ocean's oxygen minimum zones.
29:33Reproducing in the midnight depths can be as challenging as feeding.
29:38A mother black-eyed squid pulls a clutch of more than 2,000 eggs through the ocean,
29:48held in membranous sacks that more than double her length,
29:52at a depth of 2 kilometers.
29:56She will carry them for up to 9 months,
30:00clinging tightly with clawed hooks,
30:02and never letting go, not even to feed.
30:05It is a once-in-a-lifetime feat,
30:10and a perilous one.
30:16As the eggs mature and the mother weakens,
30:19her body begins to deteriorate,
30:22and her muscles waste away.
30:25Unable to jet away,
30:27she is an easy target for predators.
30:31Swimming is a burden, yet essential.
30:35Through her movements,
30:37the mother flushes water through the eggs,
30:39and oxygenates them.
30:41If she survives the last few months,
30:44her final act of motherly love won't have been in vain,
30:47her sacrifice bearing new life,
30:50as the young embark on their own journeys through the void.
30:54Even so,
30:56it's unknown just how many,
30:58from her clutch of thousands,
30:59will survive to brood eggs of their own.
31:02Of the more than 700 cephalopods known to science,
31:10the black-eyed squid is one of just a few
31:13that dare to carry their progeny through the dark.
31:21But they're not the only single parents.
31:23A barrel amphipod,
31:32or phronema,
31:33carves out a gelatinous protective home
31:35from the carcass of a salp.
31:40Imagine a squirrel
31:42taking over the corpse of a cat.
31:44She repurposes the body as a mobile home
31:48and nurtures her offspring
31:50on the lingering remnants of flesh.
31:54Some larvae must brave the dark alone,
31:57like this benthic lobster larvae,
31:59or leptocephalus,
32:02the transparent larval form of elopomorphs.
32:04One of the most diverse taxonomic groups of fish,
32:14containing tarpons,
32:16bonefish,
32:17and all-known eels.
32:20More than 800 species of fish
32:22begin their lives this way,
32:24feeding on sinking particles of marine snow.
32:27Some remain at this life stage
32:37for more than a year
32:38before they metamorphose.
32:42Generally,
32:43the more complex a structure or environment,
32:46the more biodiversity it's able to support.
32:49But in deep midwaters,
32:51where there are no structures at all
32:53and no solid surfaces,
32:55the only form of shelter to be found
32:57is other animals.
33:00Large organisms become drifting arcs,
33:03lifeboats,
33:04hosting a troop of smaller animals.
33:07Some are simply hitchhikers.
33:10The crustaceans on this blob-top jelly
33:11cause little harm or hindrance to the host,
33:14yet they benefit by securing a hiding place.
33:17Others are parasites,
33:20like these amphipods,
33:21feeding on a selp.
33:27This pelican eel
33:30sports a parasitic copepod
33:32that has wrapped itself around the internal organs
33:34and pierced the digestive tract
33:36with barbed mouthparts.
33:39The two streamer-like structures
33:41that trail behind it
33:42are strings of eggs.
33:44Within the bag-like veil
33:52of a shape-shifting deep star-ear jelly,
33:55an Aneuropus amphipod
33:57eats away at its host's delicate skin.
34:00It must strike a careful balance,
34:04ensuring it doesn't overindulge
34:06or it risks eating itself out of its hiding place.
34:13Deep star-ear is unusual among jellies,
34:17belonging to a group known as the ulmarids,
34:21many of which lack true tentacles.
34:24As a result,
34:25it feeds in an unusual manner,
34:27engulfing prey,
34:29before pulling the opening of its bell closed
34:32like a drawstring bag.
34:33Its digestive system
34:36adorns the bell in a mesh-like pattern,
34:39spread thin
34:40to distribute nutrients
34:41across its great surface.
34:55Other ulmarids without tentacles
34:57have developed their own feeding strategies.
35:00The big red jelly,
35:04Tiburonia,
35:05has a bell like a beach ball
35:07and stubby finger-like arms,
35:10lined all over
35:11with tiny wart-like concentrations
35:13of stinging cells.
35:14The giant phantom jelly,
35:36Stygio Medusa Gigantea,
35:38has arms like curtains
35:40that can reach 10 metres in length,
35:43draped through the water column.
35:50This is the largest of the ulmarids,
35:54and one of the largest
35:55of all known jellyfish in the ocean,
35:59sometimes found as deep
36:01as 6,700 metres
36:03in the ocean's
36:04hadal zone.
36:16The arms are thought
36:17to lack stinging cells altogether
36:19and are used
36:21to swathe and engulf prey
36:23within the enormous bell,
36:24which it can expand
36:25by up to five times.
36:31The phantom jelly participates
36:45in another form
36:46of ecological relationship.
36:50It forms a partnership
36:52with a fish
36:53called a pelagic brocula,
36:55seen here,
36:56orienting to the jelly's surfaces.
36:58The great bell of Stygio Medusa
37:08provides shelter for the fish,
37:10which in turn removes parasites
37:12from the surface of its protector.
37:13Studies into this relationship
37:26have found evidence
37:27that this fish can return
37:28to its partner if separated,
37:31for its body is lined
37:32with specialised neuromasts,
37:34sensory organs,
37:36highly sensitive
37:36to low-frequency water movements,
37:39like those created
37:40by the pulsing
37:40of the Medusa's bell.
37:43In a sense,
37:46they work together
37:47through a mutualistic
37:49symbiotic association.
37:56It's a way of life
37:58shared by countless pairings
37:59throughout the natural world.
38:04In the ocean depths,
38:06the collaborative confluence
38:07of life through symbiosis
38:08is especially important,
38:10for the perils of this great expanse
38:12pose a challenge for all.
38:13However, the jellyfish
38:18and other gelatinous organisms
38:20appear to have mastered this place.
38:24They are almost perfectly adapted
38:26to a three-dimensional watery world,
38:29without structure,
38:30beyond the reach of time.
38:33One of very few animal groups
38:35helped and not hindered
38:36by the lack of complexity.
38:38In this void,
38:41the plasticity of their basic morphology
38:43means they can grow
38:44to extraordinary sizes
38:45and take on a multitude of shapes
38:48that allow them to move and hunt
38:49in ways other more complicated animals cannot.
38:54The life cycles
38:55of deep-sea gelatinous organisms
38:57are still largely unknown.
39:00While some survive the expanse
39:02by finding shelter in others,
39:04there is one group
39:05that seems to have found a solution
39:07to being tiny
39:08in a place so vast.
39:17Siphonophores
39:18This is not truly
39:22a single organism.
39:24It is closer to a colony.
39:28A modular being,
39:30composed of tiny individuals
39:31called zoids.
39:34These are each clones,
39:36genetically identical,
39:38but their functions and anatomy
39:39are altered through mutations
39:41so that different zoids specialize
39:43and take on specific tasks
39:45to ensure the survival of all.
39:49Along a central stem,
39:52these zoids attach,
39:54confined to set regions
39:56where they remain
39:57and carry out their role.
40:01Gastrozoids are the feeding polyps.
40:04These zoids each dangle a tentacle
40:06for capturing and digesting food
40:08and nourish the other zoids
40:10via the stem.
40:13Nectophores resemble tiny jellyfish.
40:18These zoids are the swimming bells
40:20responsible for coordinating
40:21the movement of the entire colony.
40:24On the tip,
40:25a gas-filled float
40:26called a pneumatophore
40:27aids buoyancy.
40:30Those that bear all three structures
40:32are Fisonect siphonophores.
40:37One of three suborders,
40:38each defined by a distinct body plan.
40:43The second are the calicoferens,
40:46possessing just two nectophores
40:48and no pneumatophore.
40:52This is the giant siphonophore,
40:54Praia jubia,
40:55one of the longest animals in the ocean,
40:59reaching 50 meters.
41:00Cisternets possess a float
41:06and a long stem of gastrozoids,
41:08but lack swimming bells,
41:11resembling little more than frayed rope,
41:14drifting only at the mercy of the currents.
41:16Meno,
41:35in the sea.
41:45This siphonophore is about to do something bizarre.
42:15It casts off portions of its own colony, splitting its stem in several places.
42:27We don't yet fully understand why.
42:31It might be dying, its structure deteriorating, but it seems too purposeful.
42:38Perhaps it's shedding weight to increase its speed and flee.
42:42Perhaps it's cloning itself, forming new colonies from the fragments.
42:59The portion that retains the nectosome swims away.
43:10The karst portions can only sink.
43:20Their zoids are still alive, but without any means of locomotion, it's uncertain for how long they will endure.
43:28Whether or not these fragments will grow new nectophores remains a mystery.
43:58In another colony, a great cloud of zoids appear to shed and break away.
44:05one by one.
44:22More than likely, these shed zoids will die.
44:35It's thought to be a defense mechanism, a reaction to the lights of the underwater robot to distract from the central colony.
44:43One by one.
45:01Gelatinous animals are so successful that they may account for as much as 40% of the biomass of the water column.
45:08A fact that eluded the scientific community until recent decades,
45:12when submersibles and remotely operated vehicles at last allowed us to witness the lives of deep sea animals with our own eyes.
45:19And the
45:49The deep sea is, without a doubt, alien to us.
46:08This great void extending far beneath the surface and at the very bottom, a place resembling another planet, colonized by the bizarre and beautiful.
46:17But there are parallels with the places we might visit in our everyday lives that just might help us to understand it.
46:24Take, for example, the forest. The cycles of life, death and nutrients are distilled here.
46:34The trees in life provide structure and complexity, like the corals and sponges of deep sea mounts or the giant jellies of the midwater.
46:42All of them a place of shelter for life.
46:47There are layers here, too. The sun-bathed canopy, like the ocean's epipelagic zone, the sunlight zone, is where the majority of photosynthesis takes place.
47:02Sunlight energy being converted into chemical energy, food that, through death, falls down, down, down through subsequent layers to nourish those living underneath.
47:14Very little goes to waste here. The rotting deadwood and leaf litter provides homes and a niche for countless detritivores, whose entire evolutionary histories tailored their form and physiology to survive on this stuff.
47:38And in the deep sea, just like here, it's the detritivores that triumph.
47:53They cycle nutrients through food webs.
47:57After death, they sink and provide a modest feast to the deep sea floor.
48:04Each year, jellyfish alone are thought to sequester two billion metric tons of carbon away from the atmosphere.
48:12This is Pelagothuria.
48:22It's not a jellyfish or a siphonophore, but a sea cucumber, related to starfish and urchins, that feeds on marine snow.
48:33Modified tube feet form a ring of feeding tentacles around the mouth and are used to capture and bring debris towards the central orifice.
48:50It is the only member of its genus and the only known species of truly pelagic sea cucumber, spending its entire life in the water column.
49:09Others spend only part of their life swimming.
49:16Anipniastes eximia, dubbed the headless chicken monster.
49:21Not all sea cucumbers can swim, but the ones that do form a crucial link between the midnight expanse and the ocean bottom beneath.
49:40Projection
49:43Day
50:01Day
50:05Way
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