The first image that comes to our minds when someone mentions ‘sharks’ is of deadly predators. Probably torpedo-shaped, streamlined creatures, huge in size armed with sharp, triangular teeth and blood thirsty eyes, hunting for their next prey. But here's an alternate image- Sharks not more than one meter long that can actually walk!
Our brains have this default image of sharks. While tending to this, we often forget to acknowledge how there are actually over 500 species of sharks that exist. While fossils suggest that there were probably more than 3000 species of sharks around 450 million years ago; yet our first instinct is to picture the only shark we know of. The one, which was the show stopper in the movie ‘Jaws’ (Even if someone hasn’t seen the movie, they know which shark I’m talking about)
Anyway, Sharks have been on the planet for almost 420 million years now. They have survived close to four of the ‘big five’ mass extinctions. Not only does that make them older than humanity, but probably, also older than Mount Everest, Dinosaurs and possibly, some trees.
After having existed for as long as mankind itself, shark’s evolutionary history has been recorded. These records demonstrate how evolution in sharks can be traced at intervals of almost hundreds of millions of years, but studies show that for the past nine million years, something has been brewing.
What Is this New Evolutionary Trait About?
In a world where even the image of a shark is enough to terrorise masses (even though there are only 80 cases of shark attacks reported on an average annually across the globe), the last thing we need to hear is that sharks have finally evolved enough to walk out of the ocean and haunt its prey on land too.
According to a new paper by Conservation International, the University of Queensland, the Indonesian Institute of Sciences, the Australian CSIRO and the University of Florida, published in the journal Marine and Freshwater Research, shows that these sharks are the most recent species to have evolved. Their new evolutionary trait enables the species to walk on top of coral reefs. Scientists behind this discovery have proclaimed that human beings are safe- as of now.
Popularly known as epaulette sharks, these walking sharks are nocturnal and feed on benthic crustaceans, worms, and small bony fish. They are mostly a meter long, on average, which is why they don’t pose a serious threat to humanity. However, their ability to withstand low oxygen environments and walk on their fins gives them a remarkable edge over their prey of small crustaceans and mollusks.
Geographically, they are limited to Northern Australia, the island of New Guinea and the satellite islands of Raja Ampat, Aru and Halmahera in eastern Indonesia. There are nine currently recognized species that call this region home. What’s surprising is that all of these benthic sharks share a unique form of locomotion where instead of swimming, they use their highly muscular paired fins to essentially ‘walk’ along the ocean floor.
This feature was brought to light by broadcaster David Attenborough, who contributed in making these shark legs famous by showcasing these bizarre prototype ‘legs’ in action and also commented on their unusual physiological adaptation to coping with hypoxic conditions during low tide periods.
Demonstrating the ability incorporated after evolving, the feature of slowing their heart rate and breathing, so as to gradually limit blood flow to certain parts of the brain which in turn helps them to stay in the more extreme tides and exploit the riches of the reef without being picked off by bigger sharks.
But How Did This Happen So Fast?
Studies have shown that there maybe a few reasons why this process of evolution could have been preponed. To start of with, one such logic could be that this particular species of sharks keeps to themselves, domesticated in their own region and undergo extensive inbreeding, which may have accelerated the rate of mutation.
Researchers even pointed out towards the fact that this new specie may have evolved after the sharks moved away from their original population, became genetically isolated in new areas and developed into new species. Their drifting away from the original species could have taken place almost two million years ago, wherein they could have either accidentally swam away, or walked across on their fins or, alternatively, could have even ‘hitched’ a ride on reefs moving westward across the top of New Guinea.
Other factors could include the dynamic reefs that are ever-changing. Their continuous flux caused by ocean change and the coral life cycle. The epaulettes’ success depends on adapting quickly to a very dynamic environment.