[Music] the global ocean covers 71% of the surface of our planet holding within a realm as boundless as it is mysterious here beneath the shimmery surface lies a bustling Oasis teeming with life where every creature plays a vital role in the intricate dance of survival but 90% of the ocean lies in a place that sits quietly out of [Music] sight in the depths below the ocean plays host to a far stranger realm the deep sea this place is a world within our world a place of Silence emptiness and [Music] darkness one where wonders are found
drifting in a formless [Music] void at the Deep's upper limit lies The Twilight Zone where the diminished light of the sun still holds Mastery over its processes it stretches from 200 M to a kilometer down beneath the waves but with the average depth of the ocean being almost four times deeper and the deepest known Point found at a depth of 11,000 M The Twilight Zone is little more than a [Music] sliver the ocean sub quent zones each command a greater [Music] expanse the midnight zone or bathy pelagic stretches to 4 km down a place so
deep that the direct influences of the Sun the waves and the tides are not felt creating a habitat that has barely changed at all in millions of years at its lower limits the abyssopelagic begins which hosts a great desert of silth on the deep ocean floor called the Abyssal plane a realm of mud [Music] dwellers at just a few sites around the world the ocean's final underworld plummets deeper still through great Rifts etched by tectonic processes these are the trenches or the hadel pelagic when it comes to unlocking their secrets each of these zones poses
a greater challenge than the last but that hasn't stopped us from trying with some success and much still unknown [Music] since the late 20th century manned and remotely operated vehicles have granted access to the deep [Music] ocean like this one R Sebastian a robot owned and operated by Schmid ocean Institute it is the size of a small car and depth rated to 4 and A2 km its range covers the entirety of the midnight zone controlled from The Sur surface vessel via R tether Sebastian shines a light on the deep and reveals a glimpse at the
veiled expanse beneath the ocean [Music] surface as the ROV descends into the midnight zone we begin to encounter obsc ities unlike anything observed near the surface some are so small that they are barely visible to the naked eye and others are giants this is a place of pure Darkness too deep for any light at tool to penetrate it's a harsh environment with a large physical distance from the Plankton that form the base of food webs limits the abundance of animals that the midnight zone can support life here must find a way to function in a
cold dark abyss where temperatures do not exceed 4° C and withstand extreme hydrostatic pressure that ranges from 100 atmospheres at the top of the zone to 400 at the bottom in spite of these challenges animals must make compromises and push their morphology and physiologies to the extreme in order to avoid Predators find food and locate mates amidst a massive pitch black void and so a set of surreal adaptations are employed [Music] soft bodies like that of the cusc can withstand the crushing pressures that would damage or kill most other [Music] creatures metabolisms are slowed [Music]
dramatically time ticks to a slower tune here it's the patient and the slow that grow [Music] old Greenland sharks belonging to the sleeper shark family are known to live for centuries 2,200 M down in the cold depths of the Artic ocean and growing longer than great whites up to 7 [Music] m like many animals down here they exhibit a phenomenon called Deep Sea gigantism the tendency of deep sea creatures to grow to sizes far exceeding those of their shallow water counterparts Predators belong to a trophic Niche you'd expect to be unsustainable in a place like
this where food is scarce enough already for the Detroit ofor so to conserve energy Predators adopt sit and wait tactics using the dark to their advance Vantage a comb jelly casts a net of tentacles lined not with stinging cells but sticky color blasts that capture prey like a spider's web [Music] strips of f fine hairlike cyia run the length of the body and are beat synchronously allowing the jelly to swim and refracting light in shimmering waves they also produce light of their own from special cells called photosites bioluminescent perhaps as a means of lowering prey
a lobate comb jelly lacks sticky tentacles it uses its cyia to create a feeding current engulfing prey while in the Twilight Zone bioluminesence is used to hide here it instead gives a voice to the lonely wanders of this midnight [Music] World a female anglerfish wields a lure called an esca filled with bioluminescent bacteria and poised at the tip of a modified dorsal finay called an [Music] alysium encounters between angler fishes happen so rarely that many have gone to extreme lengths to maximize their reproductive success they exhibit exceptional sexual dimorphism the males display no eser and
are dwarfed in size by the females yet possess large eyes and nostrils that allow them to detect the species specific pheromones of the female and once he finds her a male will develop a pincer-like pair of tentacles in his jaw and latch on permanently to the female's body their circulatory systems combine and the male reduces to nothing more than a shriveled sperm producing Sac nourished and sustained by the female's [Music] blood efficiency is key in the ocean and every aspect of an organism's anatomy and behavior is optimized to solve the challenges they face body shapes
make a world of difference depending on the environment they [Music] inhabit in the sunlet waters of the high seas predatory fish spend most of their lives on the [Music] hunt water is 800 times more dense and 50 times more viscous than air making it a challenge to move through for a predator it helps to be streamlined with a rigid forked tail like that of the tuna this is a fusiform body type it minimizes inertial drag and allows tuna to migrate more than 15,000 km in a year at times reaching 43 mph fishes of the reef
are compressed they require agility not speed and so are flattened side to side for quick accurate turns and darting among coral and [Music] rock on the sandy sea floor fish are flatten with depressi bodies [Music] but what about here in the ocean's midnight void food is too scarce to support streamlined Predators there is no Rock to Dart among for cover nor any floor for [Music] Miles there are two body types that seem to dominate rounded globo form fish like Anglers are suited not for sustained swimming but floating in weight of prey to come within [Music]
reach others like the sore tooth eel are elongate and flexible anguila form this form not only allows it to conceal its silhouette by hanging vertically when it Ventures into Twilight Waters but enables it to move in a series of sinuous waves that pass along the body and produce propulsive thrust for efficient swimming [Music] the snipe eel moves in a similar way but is thinner and more thread shaped with a body type known as phof form the jaws of its bird-like beak curve away from each other at their tips covered with tiny hooked backward pointing teeth
for trapping minute crustations like shrimp as it sweeps through the water permanently a gape the snipe eel also boasts the most vertebrae of any animal on Earth with more than 700 along its meter and a half long [Music] body as fishes like these move flexible throughout their entire length the undulatory wave passes backward with increasing amplitude and speed producing the highest propulsive thrust in the [Music] tail it offers the most efficient method of locomotion in a place so starved of energy without compromising on speed as the Anglers have not being restricted to sit and wait
tactics unlocks an assortment of feeding behaviors for anguilliform fishes like the oversized mouth of the gulper it is larger than the rest of the body and can be opened wide enough to scoop up shs of shrimp or swallow animals much larger than itself a pouchlike lower jaw holds the prey while its stomach distends within to accommodate and digest the feast there is a clear Trend too in the color of fishes here compared to the Twilight Zone the shimmering silvery fishes are fewer and instead a host of dark brown or black fishes Prevail many boast an
adaptation called Ultra Blackness with a surface covered in melanosomes containing extraordinarily high concentrations of the pigment melanin that reflects in some instances less than half a percent of the light that falls upon them it's in stark contrast to the reflective guanine crystals that allow silvering in fishes of The Twilight Zone where being so dark would only make their Silhouettes stand out in the sun's residual glow down here it's a superpower light organs located beneath each eye of this shiny loose jaw dragon fish produce red bioluminescence that serves as a search light pray that a bright
red in color which typically appear black down here stick out like a sore thumb in the red glow the black belly Dragonfish foro Ultra blackness in favor of brassy bronze skin using a bioluminescent barbell on its chin that acts like an angler [Music] lure the large backward-facing teeth of the toothy viper fish are too large to fit inside its mouth but they act like a cage ensuring prey can't escapee once captured [Music] its fangs are formed from Crystal Nano structures so small that wavelengths of light pass through instead of scattering rendering them invisible to [Music]
prey adorning the undersides of Dragon Fishes our bioluminescent dots used for counterillumination matching any light above when seen from [Music] below the Pacific black chin scopal lenis tristis has only been filmed in its natural environment a small number of times in many of these encounters it remains motionless perhaps to avoid being seen like the bronze dragon fish its silvery scales only shine when illuminated by the lights of an underwater robot but in the dark May scatter light and obscure the shape of the body very little is known about their life history like many fishes that
hail from such depths Chimera is one of the oldest fish in the ocean an ancient relative of sharks that diverged from a common ancestor 200 million years ago running along its entire length is a lateral line system resembling Patchwork for sensing movements in nearby water for every 10 m we descend pressure increases by one atmosphere to survive fish have evolved strengthen protein structures and more fluid cellular membranes that preserve their vital biological functions for others including many spilop pods a soft gelatinous body is all they need to overcome the pressure and maintain neutral [Music] buoyancy
water cannot be compressed so being composed primarily of water helps out down here the Dumbo octopus flaps a pair of enlarged ear-like mantle fins to move gracefully staring with webbed arms as it traverses the void reaching depths of 6,000 M it is the deepest living octopus of all pressure at the lower end of its range can be 600 times greater than at sea level equivalent to the weight of 50 jumbo Jets although to us the conditions of the deep appear extreme the features that Define a challenging environment are always [Music] relative for 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 [Music] of The deeps Eclectic tapestry of animals the seapods are perhaps the most enigmatic displaying physiological morphological and behavioral modifications to become masters of this world each of them ethereal dancers pushing the boundaries of adaptation to sculpt an existence uniquely their own [Music] [Music] they dominate in a range of forms displaying unusual appendages for feeding [Music] the long sticky feeding tentacles of the Whiplash squid mtig opsis are draped like fly paper into the water below
termed The Tuning Fork position as it basks in a cloud of its own ink [Music] [Music] [Laughter] [Music] [Music] when it's time to move on the tentacles are retracted into membranous sheaths within the Squid's arms [Music] the large eye of the strawberry squid allows it to spy the Silhouettes of animals above against the deep blues of The Twilight [Music] Zone by day it resides at the very bottom of this C at around 1,000 M down where a backdrop of fading light transitions to pitch [Music] black it positions Itself by turning or ratcheting its body so
that a second smaller eye peers down into darkness looking for luminous pre dimorphism in the eyes of bilateral animals is rare and yet for the strawberry squid serves as a unique adaptation that allows it to carve out a niche in a place where resources are few and competition is high [Music] on the topic of resources brilliant has very kindly sponsored natural world facts brilliant is where you learn by doing with thousands of interactive lessons in maths data analysis programming and AI it's a learning platform designed to help you build understanding from the ground up with
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subscription now let's Journey Back Down Into the Depths the boundaries of the ocean zones are not clearcut the Twilight and midnight regions both belong to the aphotic Zone defined as the depths Beyond which less than 1% of sunlight penetrates a place often referred to as the dark ocean while some animals are adapted to either the Twilight Zone tailored to a place where light is diminished But Not absent or the midnight zone swallowed by pitch black others are able to span both in such cases it helps to be born with an invisibility [Music] cloak aside from
the eye is optic nerves and a long narrow digestive system this glass octopus is almost entirely see-through this one is a male the small hook-like tip of one tentacle is a modified sexual organ called the hecta cocalis used to pass sperm to the female [Music] [Music] a mature female reaching around 45 cm [Music] her body is speckled with color producing cells called chromatophores that she uses for camouflage small muscles can expand to pull open the pigment Sachs darkening her [Music] body it's the same mechanism behind the color color changing abilities of many other spilop pods
laid bare by a transparent [Music] body in the midnight zone the feeding behaviors of squids and octopuses differs greatly from those of Twilight animals above in the misop pelagic life is fastpaced owing to the higher abundance of prey squids here hunt in groups swarming and inking to confuse schools of [Music] fish among the largest to do so are the Humbolt squib launching tentacles lined with barbed suckers to grab silvery lantern fish [Music] [Music] [Music] scenes like this are a nightly occurrence in the Twilight Zone initiated by the slightest changes in ambient light as the sun
sets calling forth great swarms of Twilight fish that gather to migrate vertically under the cover of Darkness this phenomenon is is one of the only reasons why large active Hunters like humbal squid are able to sustain such an energetic lifestyle in the bathy pelagic you must be opportunistic to succeed schooling fish are few but sinking organic debris is plentiful Marine snow the scraps left over from the feasts [Music] above in a velvet cloak the vampire squid dangles a long filamentous tentacle covered in adhesive mucus to trap these fine particles [Music] It is Well Suited to
a place starved of not just food but oxygen its blood contains a respiratory pigment hemocyanin that has the highest affinity for oxygen of any known spilop pod thus the vampire squid can reduce competition from other detritivores by occupying the ocean's oxygen minimum zones [Music] reproducing in the midnight depths can be as challenging as feeding a mother blackeyed squid huls a clutch of more than 2,000 eggs through the ocean held in membranous sacks that more than double her length at a depth of 2 km she will carry them for up to 9 months clinging tightly with
clawed hook and Never Letting Go not even to feed it is a once in a-lifetime feet and a perilous one as the eggs mature and the mother weakens her body begins to deteriorate and her muscles waste away unable to Jet Away she is an easy target for Predators swimming is a burden yet essential through her movements the mother flushes water through the eggs and oxygenates them if she survives the last few months her final Act of motherly love won't have been in vain her sacrifice bearing new life as the young embark on their own Journeys
through the void even so it's unknown just how many from her clutch of thousands Will Survive to brw eggs of their their [Music] own of the more than 700 seapods known to science the blackeyed squid is one of just a few that dare to carry their progeny through the dark but they're not the only single [Music] parents a barrel amphipod or frima carves out a gelatinous protective home from the carcass of a salp imagine a squirrel taking over the corpse of a cat she repurposes the body as a mobile home and nurtures her Offspring on
the lingering remnants of Flesh some lvi must Brave the dark alone like this benthic Lobster ly or lepto cilis the transparent lavel form of [Music] elopomorph one of the most diverse taxonomic groups of fish containing tarpons Bone Fish and all known eels more than 800 species of fish begin their lives this way feeding on sinking particles of marine snow some remain at this life stage for more than a year before they metamorphose generally the more complex a structure or environment the more biodiversity it's able to support but in deep midw where there are no structures
at all and no Solid Surfaces the only form of shelter to be found is other animals large organisms become drifting arcs lifeboats hosting a troop of smaller animals some are simply hitchhikers the crustations on this blob toop jelly cause little harm or hindrance to the host yet they benefit by securing a hiding place others are parasites like these amphipods feeding on a s this Pelican eel Sports a Paris itic Copa pod that has wrapped itself around the internal organs and pierced the digestive tract with barbed mouth Parts the two streamer likee structures that trail behind
it are strings of eggs within the bag likee Bell of a shape-shifting deep staria jelly an an Europa sod eats away at its host's delicate skin it must strike a careful balance ensuring it doesn't overindulge or it risks eating itself out of its Hiding Place deep staria is unusual among jellies belonging to a group known as The alids Many of which lack true tentacles as a result it feeds in an unusual manner engulfing prey before pulling the opening of Bell closed like a drawring bag its digestive system adorns the bell in a mesh-like pattern spread
thin to distribute nutrients across its great [Music] surface other mids without tentacles have developed their own feeding strategies the big red jelly tiberon has a bell like a beach ball and stubby finger-like arms lined all over with tiny wart-like concentrations of stinging cells [Music] the giant Phantom jelly stigo Medusa gigantia has arms like curtains that can reach 10 m in length draped through the water column this is the largest of the alits and one of the largest of all known jellyfish in the ocean sometimes found as deep per 6,700 m in the ocean's hadle [Music]
Zone the arms are thought to lack stinging cells altogether and are used to S and engulf prey within the enormous Bell which it can expand by up to five times [Music] the Phantom jelly participates in another form of ecological relationship it forms a partnership with a fish called a pelagic brula seen here orienting to the Jelly surfaces the great Bell of stigo Medusa provides shelter for the fish which in turn removes parasites from the surface of its protector studies into this relationship have found evidence that this fish can return to its partner if separated for
or its body is lined with specialized neuromasts sensory organs highly sensitive to lowf frequency water movements like those created by the pulsing of the Medusa's Bell in a sense they work together through a mutualistic symbiotic Association it's a way of life shared by countless pairings throughout the natural world in the ocean depths the collaborative Confluence of life through symbiosis is especially important for the Perils of this great expanse pose a challenge for all however the jellyfish and other gelatinous organisms appear to have mastered this [Music] place they are almost perfectly adapted to a three-dimensional watery
world without structure beyond the breach of time one of very few animal groups helped and not hindered by the lack of complexity in this void the plasticity of their basic morphology means they can grow to extraordinary sizes and take on a multitude of shapes that allow them to move and hunt in ways other more complicated animals cannot the life cycles of deep sea gelatinous organisms are still largely unknown while some survive the expanse by finding shelter in others there is one group that seems to have found the solution to being tiny in a place so
vast siphonophores this is not truly a single organism it is closer to a colony a modular being composed of tiny individuals called zoids these are each clones genetically identical but their functions and Anatomy are altered through mutations so that different zoids specialize and take on specific tasks to ensure the survival of all along a central stem these zoids attach confined to set regions where they remain and carry out their role gastro zooids are the feeding polyps these zoids each dangle a tentacle for capturing and digesting food and nourish the other zoids via the stem nectop
fores resemble tiny jellyfish these zoids are the swimming Bells responsible for coordinating the movement of the entire Colony on the tip a gas-filled float called aapor AIDS buoyancy those that Bear all three structures are fisin [Music] siphonophores one of three suborders each defined by a distinct body [Music] plan the second are the copin possessing just two Nector and no newator this is the giant siphonophore prer juia one of the longest animals in the ocean reaching 50 m cects possess a float and a long stem of gastroids but lack swimming Bells resembling little more than frayed
rope drifting only at the mercy of the currents [Music] [Music] [Music] this siphona 4 is about to do something bizarre [Music] [Music] it casts off portions of its own [Music] colony splitting its stem in several places we don't yet fully understand why it it might be dying its structure deteriorating but it seems too purposeful perhaps it's shedding weight to increase its speed and flee perhaps it's cloning itself forming new colonies from the [Music] fragments the portion that retains the isone swims [Music] away the cast portions can only sink their zoids are still alive but without
any means of locomotion it's uncertain for how long they will endure whether or not these fragments will grow new nectar Force remains a mystery [Music] [Music] in another Colony a great cloud of zoids appear to shed and break away one by one more than likely these shed zoids will die it's thought to be a defense mechanism a reaction to the lights of the underwater robot to distract from the central colony [Music] gelatinous animals are so successful that they may account for as much as 40% of the biomass of the water column a fact that eluded
the scientific Community until recent decades when submersibles and remotely operated vehicles at last allowed us to witness the lives of deep sea animals with our own eyes [Music] the deep sea is without a doubt alien to us this great void extending far beneath the surface and at the very bottom a place resembling another planet colonized by the bizarre and beautiful but there are parallels with the places we might visit in our everyday lives that just might help us to understand it take for example the forest the cycles of Life Death and nutrients are distilled here
here the trees in life provide structure and complexity like the corals and sponges of deep sea mounts or the giant jellies of the midwater all of them a place of shelter for [Music] life there are layers here too the sunbathed canopy like the ocean's epipelagic Zone the sunlight zone is where the majority of photos synthesis takes place sunlight energy being converted into chemical energy food that through death falls down down down through subsequent layers to nourish those living [Music] underneath very little goes to waste here the rotting Deadwood and leaf litter provides homes and a
niche for countless Detroit of ores whose entire evolutionary histories tailored their form and Physiology to survive on this stuff and in the deep sea just like here it's the Detroit of wars that Triumph they cycle nutrients through food webs after death they sink and provide a modest Feast to the deep sea floor each year jellyfish alone are thought to sequester 2 billion metric tons of carbon away from the [Music] atmosphere this is Pago theia it's not a jellyfish or a siphonophore but a sea cucumber related to starfish and urchins that feeds on Marine [Music] snow
modified tube feet form a ring of feeding tentacles around the mouth and are used to capture and bring debris towards the central orifice it is the only member of its genus and the only known species of truly pelagic sea cucumber spending its entire life in the water [Music] column others spend only part of their life [Music] swimming and nip nastes eximia dubbed The Headless Chicken monster [Music] not all C cucumbers can swim but the ones that do form a crucial link between the midnight expanse and the ocean bottom beneath at the bottom of the midwater
we reach the intersection of two worlds of the deep where from the formless void at last emerges structure [Music] the deep sea floor a world shaped over millions of years by unique geological processes carving ridges and chasms crafting subsea mountains ranges adorned by colorful Gardens flourishing cities of coral and sponge and on the plains Beyond a great desert where animals work the sediments a community of burrowers rers hitchhikers and Bottom Feeders etching trails in the ancient silt [Music] beds and Scattered boneyards where Great Gatherings of scavengers convene to Feast on the remains of giants this
is a territory of obscurities kept secret and concealed away in the dark at the bottom of the ocean's void the deep sea Plains cover more than half the surface of the Earth hosting their own anthology of tales of Life In The Deep [Music] [Music] is [Music]
