Why Sharks get Creepier the Deeper you Go
When we think of sharks, many of us think of them as mindless killers. But they are much more then just mere monsters, they are highly specialized predators that have been patrolling the oceans for over 450 Million years. There streamlined shapes and greyish blue colors are the common adaptions of open ocean we have come to know well, which have helped them in their quick and camouflaged pursuit of prey, but this is just the tip of the iceberg.
Primitive sharks evolved 450 million years ago, and broke off about 420 Million years ago, we got the Chimaera, which are classified now as an entirely different species, that looks like an alien fish, but are from the same common ancestry as the shark
It was 195 Million years ago, the Hexanchiforms appeared. These are much closer to the sharks we know today with long slender bodies, and flexible protuding jaws, allowing them to pursue and eat prey much larger than themselves.
We know from fossil record that older shark ancestors had 6-7 gills, and modern open ocean sharks have 5 gills. The current inhabitants of the deep have 6-7 gills still to this day, because the deep ocean has less ocean per unit of water than ocean water closer to the surface. This is a strong indicator that the deep ocean sharks are closer relatives to the ancient shark's, and that sharks seemed to have evolved up from the deep.
Sharks from the deep also have much larger eyes, and can have bioluminescent properties, to help them navigate the darkest depths of the oceans where significantly less light reaches the world of constant night.
Deep sea sharks are on average much much larger than open ocean sharks. The Greenland shark grows to 24 Feet, far larger than the more popular great white shark.
This a phenomenon known as "deep sea gigantism". This is when species grow much larger then their average shallow water counter parts. This is because larger animals lose heat slower, preserve energy and be more calorie efficient in the nutrient deprived deep sea.
Deep sea sharks also have incredibly slow moving metabolisms and move incredibly slow. This slow moving life style allows them go months without eating, and live quite long, in fact, the longest living vertebrates, living up to 500 years!.