Deep sea creatures: the amazing under-explored part of the world

The deep seas

Despite being the most inhospitable environment on Earth, the deep sea is home to an astonishing variety of life. It is puzzling how such a wide variety of species could have evolved in the face of such seemingly inhospitable habitats – and yet they have. Deep sea vents and nutrient flow are likely contributing factors.

According to deep sea ecologist Dr. Ramirez-Llodra, at the Norwegian Institute for Water Research, typically, the ocean floor below 656 feet (200 meters) is usually termed the deep sea, an area where sunlight is sparse and primary production is limited. 

Per Ramirez-Llodra, abyssal plains, areas in excess of 3,000 meters of ocean depth, cover over half of Earth's surface. Therefore, it is important to remember that the deep sea is not an exceptional environment; rather, for much of the planet, it is the norm, while terrestrial ecosystems are actually less common.

The exact number of marine species is a mystery that has yet to be solved by experts, but an estimated 240,000 marine species are known to exist today. Yet, there is concern that marine ecosystems are in decline owing to human activities such as increasing water temperatures and waste. 

However, new species are continually being discovered, and anything from a hundred thousand to a million additional species are thought to exist but remain unfound.

Over the past few decades, the deep seas have provided a treasure trove of data on animal evolution. 

Adaptation and evolution 

Just like all life, the animals that live in the ocean's depths have evolved or adapted to their environment. Constant low temperatures, total darkness, and intense underwater pressure are all part of this environment. These creatures, for instance, may utilize hydrothermal vents in the deep sea to thrive and survive at such high pressures, low temperatures, in the absence of light, and in the presence of hazardous substances like polychlorinated biphenyls (PCB) and polybrominated diphenyl ethers (PBDEs).

Deep sea fish tend to be tiny and soft, with little bones. Several species of deep-sea fish have evolved the ability to produce their own light, which they use bioluminescence to emit. These glowing organs attract both prey and prospective partners.

What are some of the more fascinating sea creatures

We’ve talked about how generally unknown the deep seas are. But the creatures we are familiar with, who make a home in these dark, cold depths, have peculiar appearances due to the extreme conditions of their habitat. Due to their sometimes garish looks, some even call them deep-sea monsters.

1. The Anglerfish

There's a good reason why the anglerfish is considered a rather scary fish. From a human perspective, it may very well be one of the ugliest creatures in the known world and one of the scariest deep sea creatures known to man. Its environment, the dark depths of the ocean floor, is one of the most hostile places on Earth.

Many of the over 200 species of anglerfish can be found in tropical shallows, whereas the vast majority inhabit the Atlantic and Antarctic Oceans up to a mile underneath the surface. They have relatively large bodies and heads with big crescent-shaped mouths brimming with sharp, gleaming teeth – their skin color ranging from dark gray to brown. The longest recorded anglerfish was 3.3 feet long. However, the majority are far smaller, typically measuring in under a foot. 

Another interesting feature of the anglerfish is its bright lure worn only by its females. This lure is a dorsal spine that protrudes above the mouth. This lure is home to photobacteria that produce light. And just like its name, it is a perfect bait to get small fish within striking distances of its sharp teeth.

2. Fangtooth

One of the weirdest deep sea creatures is the fangtooth fish, which has a large jaw that can protrude out into the water.

Fangtooths are deep-sea predators. There's also an eel called the fangtooth moray, but it's found in a very different environment than the fangtooth fish. 

Younger, smaller fangtooth fish filter zooplankton from the water and adults feed on fish, crustaceans, and squid.

In proportion to their body size, their teeth are the biggest of any marine animal. Special pouches on the roof of its mouth prevent the teeth from piercing the fish's brain when its mouth is closed.

The zone where fangtooth fish thrive is called "the twilight zone," about 650 to 3,300 feet (200 to 1,000 meters) below the ocean surface.

Like many other marine organisms, fangtooth fish are drab in color, and to many, they have an unsettling appearance.

3. Sea Sapphire Copepods

The sea sapphire, also known as the Sapphirina, is a tiny crustacean that is a genus of parasitic copepod. These direct phytoplankton feeders are called "sapphire of the water" due to their iridescent, translucent skin, which causes them to seem to shift colors under different lighting conditions. 

This quality results from minuscule hexagonal crystal plates that reflect specific wavelengths of light. Because of this, depending on the lighting, the crustacean might become undetectable to the naked sight. 

When hundreds of Sapphirina are floating on the water's surface, it gives the impression that the ocean is coated in diamonds. They can appear in hues from bright golden to deep blue, depending on the lighting. Yellow, orange, and red sea sapphires are found closer to the surface of the sea, while greens, blues, violets, and magentas are found deeper, where only light from shorter wavelengths can penetrate.

Female Sapphirina, which parasitize gelatinous creatures, are significantly less bright than their male counterparts. These copepods may be found in the waters of Asia, the Americas, and Africa.

4. Stoplight Loosejaw

Stoplight loosejaws, members of the dragonfish genus Stomiidae, are some of nature's most cunning predators. A pair of light-emitting organs located just below each eye gives them their name; these produce green and red lights, respectively, much like a traffic light. Stoplight loosejaws have a distinct edge when seeking food and avoiding predators since most marine organisms cannot sense red light waves. 

They inhabit regions between 1,700 and 13,000 feet deep in the ocean. 

Unlike most dragonfishes, the stoplight loosejaw spends most of its life deep below the surface.

Despite their massive jaws and teeth, these fish eat mostly zooplankton, with the occasional fish, shrimp, and krill to balance their diet. 

The lower jaw of a stoplight loosejaw is approximately one-quarter as long as the rest of the animal, and it is permanently wide open. A broad gape and a propensity for the mouth to hang open make this fish an outstanding specimen. They have numerous rows of pharyngeal teeth that assist in transporting food up the esophagus and a huge, fang-like set of teeth towards the front of the jaw.

Stoplight loosejaws resemble dragons of the sea, as their family name suggests. They have long, slender frames that are topped off with big eyes and small, rounded noses. They're around 1 foot long on average. Both the dorsal and anal fins have around 20 rays and are located at the back of the body. They have the thin, scaleless skin and mostly black or gray coloring of other stomiid and deep-sea fish.

5. Sheepshead Fish

The bodies of sheepshead fish have an interesting look; they are often silver or gray in color with five to seven vertical black streaks. These fish are among the most unusual in the ocean, with a single dorsal fin and an arched back behind the head. Because of the resemblance of their patterns to prison garb, these fish are sometimes also referred to as Convict Fish.

Their human-like teeth are unique features of this deep sea fish; they have incisors (like human front teeth) and molars (back teeth) in their mouths.

Twelve strong and rigid spines make up the dorsal fin, with softer spines near the tail. As a kind of self-defense, these spines make the fish appear bigger and more dangerous than they actually are. 

The maximum length of a mature sheepshead is 36 inches, and its maximum weight is 21 pounds. 

6. Barreleye Fish

The barreleye fish, or spook fish, is a deep-sea creature with a remarkable adaptation that allows it to see in nearly pitch-black waters. And their entire scalp is see-through.

Studies have found that this translucent membrane covering their heads helps to prevent the siphonophores' stings from reaching their eyes. 

To the untrained eye, this fish's eyes appear to be fixed in an upward gaze. Scientists had assumed this until 2019 when they learned the barreleye could actually spin its eyes. They are actually upward-pointing and able to spot prey above them in the water and can rotate forward when needed.

The depth of the Barreleye fish's habitat ranges from 2,000 to 2,600 feet. They feed on tiny crustaceans, siphonophores, and other zooplankton.

7. Sea Spider

Deep sea spiders have been discovered as far down as 2,300 feet. These bottom-dwellers may be found in every ocean on the planet and subsist on sea nettles, sponges, and other slow-moving marine organisms. Some species have sharp claws to better seize their food. 

Sea spiders may resemble terrestrial spiders, but they are not the same. The Arachnida class includes the spiders we see on land. In contrast, sea spiders belong to the order Pycnogonida. There are, nevertheless, some shared features between the two – they share some characteristics, such as being arthropods.

They share an ancestor with crabs and spiders, but sea spiders have been evolving on their own for hundreds of millions of years. Scientists have even discovered a sea spider larva that is 500 million years old.

8. Frilled Shark

The frilled shark is one of the scariest deep sea creatures due to its prehistoric-looking eel-like body and snake-like head. It has extremely long, thin teeth with three cusps. This fearsome beast of the deep may be found at depths of up to around 4,500 feet below the ocean's surface but is also found higher in the water column.

The frilled shark, with its jaws gaping to lure in prey, moves silently in the depths of the sea. Although its jaws make the creature appear more menacing, scientists believe it really serves as a form of bait to lure in potential meals. Most of this terrifying animal's diet consists of squid, although they may also feed on larger fish – even sharks. 

According to scientists, one of the oldest sharks in the ocean is the frilled shark; it has been around for millions of years. In addition, studies reveal that they have altered little throughout that time.

9. Giant Isopod

Giant isopods are bottom feeders found at depths of around 1800 feet, but they have been known to go as deep as 7,000 feet. They are scavengers that feed on marine life that falls to the ocean floor, including crabs, fish, squid, sea sponges, and much more. Due to the scarcity of food in the ocean below, giant isopods have adapted to go for extended periods of time without eating, thanks to their very slow metabolism. 

Giant isopods, when threatened, can curl into a ball like the land-dwelling pill bugs they resemble. This is largely facilitated by the fact, like other crustaceans, they have no spine and instead have a segmented shell, which helps to protect their internal organs. They are safe from harm because of their hard exterior. They have adapted to periods of up to five years with no food, but when food is available, they will happily gorge themselves.

10. Deep-sea viperfish

The deep-sea viperfish is another species of Stomidae. This predatory marine animal is one of the deep sea's most successful carnivores. Their long, lean body and huge, clear, sharp teeth help them hunt in the deep sea's pitch-blackness. Their glassy teeth interlock to form a cage in which to trap their prey.

These see-through teeth are made of enamel and dentine and scatter very little light. This means the fish’s teeth don’t twinkle in the bioluminescent lights produced by many animals in the deep sea.

Deep sea viperfish spend the daytime hours at depths of up to 5,000 feet below the surface of the ocean. At this depth, however, food is quite sparse. As a result, they move up to depths of around 2,000 feet at night, where there are more fish and other marine life suitable for consumption. 

Seeing as how deep sea viperfish live so far down in the ocean, very little is known about them. Many scientists believe that they spawn externally, with females releasing eggs into the sea. Information about this species is scant since scientists usually only learn about it if one is brought in by unwary deep-sea fishers.

Creatures of the deep sea may be terrifying to some, but they really are truly incredible. Unfortunately, many common misconceptions about these fascinating animals persist. For one, many of the frightening characteristics that give these creatures their alarming appearance are, in fact, crucial to their very survival. 

The chance of you ever encountering one is extremely low; however, aren't they simply amazing? And you just never know; having knowledge about these deep sea creatures just may come in handy someday.