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Aliens of the Deep
The deep sea is the largest and most mysterious habitat on our planet. Taking up 95% of the Earth’s living space, it remains largely unexplored. It’s hard to imagine anything surviving in the pitch black, icy cold, crushing environment of the deep ocean, yet scientists are discovering a habitat rich with life. The creatures being uncovered are often so bizarre they might seem, at first glance, like aliens.
In November 2015, photographer Solvin Zankl accompanied a scientific expe-dition to the Cape Verde Islands in the eastern tropical Atlantic, where his mis-sion was to document the strange crea-tures living beyond the reach of the sun. ‘There is no other place on earth where you can photograph such interesting-looking animals,’ says Zankl, a trained marine biologist with a lifelong fascina-tion for life under the waves.
Photos by Solvin Zankl / naturepl.com
The MARIA S. MERIAN left the port of Las Palmas, Gran Canaria, on 28 No-vember 2015 and sampled the waters around the Cape Verde Islands in the eastern tropical Atlantic between 30th November and 20th December. The aim of the cruise was to assess the pelagic (open ocean) fauna in the waters around the islands. Solvin Zankl (pictured in the back row, far left) was assigned to photograph samples as they were brought to the surface. All photos were taken in a tank, kept in a cold room at a constant tempe-rature of 4°C.
The sampling programme included both netting and opti-cal systems in order to assess a wide variety of species at depths between 150 - 1000 metres.The nets used to capture deep sea organisms [see below] can damage fragile gelatinous species, or even fail to capture them altogether. Therefore, a recently developed optical sam-pler called the PELAGIOS was also deployed [left]. This is a towable observation instrument that consists of an aluminium frame, HD cameras in pres-sure-proof cases, light arrays and LEDs, which illuminate the water around it.
Zooplankton are species that spend their entire life cycle drifting in the water column. They are typically small, and often microscopic, but some (such as jellyfish) are larger and visible to the naked eye. The zooplankton pictured here are not shown to scale.
Zooplankton play a critical role in main-taining the health and balance of the ocean and its complex food webs. They break down and consume dead plant and animal material that falls through the water column as ‘marine snow’, and in turn, they become food for secondary consumers such as fish.
[Below] Juvenile deep water pelagic octopus (Vitreledonella richardi), also known as the glass octopus. Little is known about this species. Its body is gelatinous and transparent, enabling a clear view of the digestive system (the long, nar-row shape above and between the eyes), as well as the gills, mouth and brain. Different life stages seem to inhabit different depths, with individuals gra-dually moving deeper as they mature.
[Right] Deep sea Pram Bug (Phronima sp.) with young in a salp house. The pram bug is a translucent amphipod (a type of crustacean). At about 2.5cm in size, it resembles a shrimp with a head, eyes, jaws and clawed arms. This species is only seen in the wild at great depths. Pram bugs hijack salps (barrel-shaped, gelatinous zooplankton which drift throughout oceans) and hollow them out to create mobile nurseries for their young
(the orange larvae can be seen inside the salp in this
image).
[Above and below]Leptocephali are the flat
and transparent larval stages of eels and other related fish.
They look very different from their adult counterparts, with laterally com-
pressed bodies filled with transparent jelly. The rib-like structures are muscle fibres called
myomeres.
[Above] Flatfish larva swim upright and have sym-metrical bodies. But as the larva develops to an adult, it begins to tip on its side and the bones in its skull shift as the right eye migrates to the opposite side of the head. The transformed flatfish sinks and settles on its blind right side. It will spend the rest of its life as a bottomfeeder, with two eyes on the same side of its head and a contorted mouth.
Boxer snipe eel (Nemichthys curvirostris)Depth Range: 0 - 2,000m
Snipe eels are characterized by their long body and very slender jaws that separate toward the tips, resembling the beak of a snipe ( a type of wading bird).
Bioluminescence commonly occurs in deep sea fish, as a result of chemical reactions in light-emitting organs called photo-phores. This dazzling glow-in-the-dark display can be used for communication, to attract prey, distract predators or even as a defence tactic.
[Above] Scaleless black dragonfish (Melanostomias biseriatus)Depth range: 620 - 760 mThe barbel hanging below the jaw of this species acts as a bio-luminescent lure, drawing prey closer to the fearsome mouth.
[Below]: Diaphanous hatchetfish (Sternoptyx diaphana)Depth range 400 - 3676 mVentral photophores of this species are thought to obscure the body outline from predators, by matching the ambience of downwelling light.
[Above] The lanternfish’s luminescent organs are pale green or blue and are located on the fish’s head, underside, and tail. The distribution of their light organs follows a design that is species-specific, with each species lighting up in a different pattern.
[Left] The cock-eyed squid is so named because the right eye is normal-sized, whereas the left eye is at least twice the diameter and bulges out of the head.
Deep-sea fish have adapted to their pitch-black environment by evolving eyes that are very good at collecting light. Some species have a tapetum, a reflective layer which bounces light back through the retina, enhancing sensitivity in low light conditions.
[Left] Deep Sea Threadtail (Stylephorus chordatus). Depth range: 300-800mThis species has tubular eyes with big lenses, capable of detecting even the slightest traces of light.
[Below] Zoea are free-swimming larvae of certain crustaceans. This crab zoea has rudimen-tary legs and large spines many times longer than its body, providing defence against pre-dators. Owing to the drastic dif-ference between the larval and adult forms, many crustacean larvae were wrongly classified when first discovered, thought to be uinque species as opposed to larval forms.
[Right]Having passed through various zoea stages, crab larvae moult into the megalopa (or post-larva) stage, as seen here. This is followed by metamorphosis into an immature form, which broadly resembles the adult. After further moults, the adult form is finally reached. Megalopa are characterised by the use of abdominal appen-dages (pleopods) for propulsion through the water.
Black dragonfish (Malacosteus niger)Depth range: 500 - 3886 m
This species has bioluminescent ‘flashlight’ organs beneath each eye. It is among the small group of deep sea fish that are able to both emit red light and see it, enabling them to lluminate their prey without the victims ever knowing about it – and without ringing the dinner bell for other predatory species.Like many of its dragonfish relatives, this species has an enormous gape. The head can hinge backwards, allowing the
jaw - which takes up over 20% of the fish’s length - to shoot out and impale prey with its sharp fangs. Surprisingly, given these fearsome adaptations, this species feeds mainly on copepods - tiny crustaceans often less than 1mm in size. Scientists believe that these small creatures provide the chemicals that M. niger uses in its eyes to see red light. When it gets the chance, however, this predator can still revert to its ancestral feeding habits and devour much larger organisms, before going back to snac-king on the copepods.
These parasitic copepods (Sapphirina sp.) are known as sea sapphires. Females are translucent, as are the males when they’re not shining. The secret to their shimmer is in the microscopic layers of crystal plates inside their cells, which refract light. Various species of male Sapphirina shine in different hues, from bright gold to deep blue. The colour is dictated by the minute distances between the crystal plates.When the distance matches a particular wavelength of light, the corresponding colour is bounced back. The angle of light reflecting off the crystal layers also changes how the animal looks. At certain angles, the reflectance passes out of the visible light range and into the invisible ultraviolet range, allowing Sapphirina to become nearly invisible.
Anglerfish are perhaps the most widely reco-gnised of all deep sea species, typically having at least one long filament sprouting from the middle of their heads (termed the illicium), which is tipped by an irregular fleshy growth (called the esca). Some deep-sea anglerfish emit light from the esca to attract prey, as well as find mates. The luminescence is produced by millions of light-emitting bacteria that breed in the esca. It has been suggested that, in some species, these bacteria are incapable of luminescence outside of the anglerfish, suggesting a symbiotic relationship between the two species.
^ Triplewart Sea Devil (Cryptopsaras couesi)
Depth range: 0 - 3085 m
Unlike the female fish, shown here, males of this species are tiny and live parasitically, becoming little more than a sperm-producing appendage.
< Johnson’s Abyssal Seadevil (Melanocetus johnsonii)
Depth range: 0 - 2,100m
Anglerfish typically have large, crescent-shaped mouths filled with translucent teeth. Coupled with a pliable body, this allows them to swallow prey larger than themselves.
^ Whipnose anglerfish (Gigantactis vanhoeffeni)
Depth range: 300 - 5,300m
Whipnose anglerfish are distin-guished by the presence of a remar-kably long lure, which may exceed the body length in some cases.
Illicium
Esca
> Juvenile glass Squid (Bathothauma lyromma).
This paralarva is very distinctive with extremely long eye-stalks and brachial pillar, which are resorbed in the subadult.
< Larva of an Atlantic longarm octopus (Macrotritopus defilippi)
This species has characteristically long arms and is known to mimic the swim-ming behaviour, posture, and coloration of a common flatfish. For a century, the adult form of this larva remained a mys-tery. It wasn’t until one was captured and cultured to adult size that it could be formally identified.
^ Squid (Abraliopsis atlantica)
This species occurs at mid-depths and undergoes vertical migrations, rising into the upper water column at night to feed.
A wide variety of cephalopods (squids and octopi) can be found in the deep sea, and many share the same general modifications such as gelatinous, trans-parent tissues, well-developed eyes and bioluminescence.
Eye stalk
Brachial pillar
o
o
Common fangtooth (Anoplogaster cornuta)
Depth range: 500 - 4,992m
This species feeds on crustaceans when young but switches to a diet of mainly fish as an adult.Relative to body size, the fangtooth has the largest teeth of any marine species; the largest two fangs of the lower jaw are so long in the adult that is has a pair of opposing sockets on either side of the brain to accommodate the teeth when the mouth is closed.
Deep sea squid typically have well-deve-loped eyes that can detect any motion or light within the environment. This specimen (Chiroteuthis mega) has cap-tured a bioluminescent lightfish in its tentacles.As a group, deep-sea squid are generally larger than their shallow water counter-parts.
‘Photographing deep sea animals is quite challenging,’ says Zankl. ‘The logistics are very difficult and the only way you can do it is in collaboration with a research institute like GEOMAR.’ ‘But I welcome the challenge. Being a marine biologist myself, documenting the immense diversity of life in the oceans is something I come back to whenever I get the opportunity. There is something very special about photographing deep sea species. You can’t take your eyes off them and they are animals which very few humans ever get to see. I hope my photographs help bring them to the attention of others.’
