The ocean, despite its size and resourcefulness, remains a mystery to humankind. It’s hard to fathom that only around 5% percent of our oceans have been explored and charted, leaving around 95% of it unexplored and unfamiliar.
Initially perceived to be devoid of life forms, the pitch-dark, freezing, and high-pressure depths of the ocean surprised many. Contrary to popular beliefs that the ocean floor only comprises of sand and marine animal carcasses that have sunk below, a plethora of marine life still thrives in this environment, where the extreme is normal.
We’ve all seen what happens to Marlin and Dory in Finding Nemo when they venture down the depths of a trench in the oceanic floor—fishes adapted to the pulverising pressure begin to emerge, whilst Dory makes out the address of ‘P. Sherman 42 Wallaby Way, Sydney’. Marine life is uniquely adapted to the pressure, temperature, and predatorial risks, assembling an alien ecosystem stranger than fiction.
deep-sea fish, like the carnivorous Anglerfish in Finding Nemo, have evolved to use several tools to lure in their prey
The Anoplogaster cornuta, a deep-sea ultra-black fish species, has evolved in such a way that its pitch-black skin protects it from predators and acts as camouflage for when it becomes the predator. But how do you blend in with absolutely nothing? The answer is copious amounts of pigment! Unlike other species of fish that use their vibrant colour to show off a little bit here and there, deep-sea fish, like the carnivorous Anglerfish in Finding Nemo, have evolved to use several tools to lure in their prey.
On the other hand, due to the hindrance in vision down in the darkness, Tripodfish use vibrations to sense their prey whilst perching on the ocean floor. The lack of sunlight makes food at the bottom sparse, so deep-sea creatures feed on decaying carcass scraps from the upper layers of the ocean. The physical properties of the deep-sea ecosystem have been described as like ‘being crushed to death in a freezer’, referring to the extreme cold and the bone-crushing pressure of these oceanic trenches.
The magic of an ocean that’s 95% unexplored is the thrill of rediscovering species that were thought to be extinct millions of years ago, such as the coelacanth, a ‘living fossil’ roaming around 2,300 feet below the surface. Thriving in these harsh conditions is the deepest known living species of fish—the Mariana snailfish, which abundantly populates the habitat 7000 meters below the ocean’s surface in the Mariana Trench.
These fish have gaps in their skulls which are thought to maintain the internal and external pressure balance
But how does this very long, and very ‘oversized tadpole’ looking thing survive in total darkness and pressures up to 1000 times more intense than in upper sea levels you ask? Studies show that these cryptic creatures are largely made from cartilage. Whereas a complete skull would crush under the pressure, these fish have gaps in their skulls which are thought to maintain the internal and external pressure balance.
Snailfish also don’t carry the gene which usually promotes the build-up of calcium to harden the bone, thereby making their bone structure flexible to the pressure. Other deep-sea animals rely on piezolyetes—small organic molecules—to avoid their proteins going crazy under high pressure, which would happen to you and me if we were to plunge down a trench.
The sheer resourcefulness of the evolutionary process in engineering such perfect survival machines never fails to bewilder the humble mammalian brain. An undiscovered world. With a plethora of aquatic species yet undiscovered, who is to say what the future encyclopaedia of deep-sea creatures holds?
Featured image of Mariana snailfish by UW News from Flickr. Image license found here. No changes were made to this image.
In article image of Anoplogaster cornuta by the Smithsonian Institution via Fishes Of Australia. Image license found here. No changes were made to this image.
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