Epaulette sharks are a small group of sharks capable of walking above and below the water on modified fins, but recent discoveries are uncovering even more interesting facts about these amazing animals.
The idea of a shark that can chase you across a beach may sound like the stuff of nightmares, but in reality the newly discovered walking sharks are about as far from a nightmare as you can get. In fact they’re kind of adorable only growing to three feet in length and spending their days plodding around the seafloor. Since 2008 four new species of these sharks, known collectively as epaulette sharks, have been discovered shedding new light on their very niche adaptations and peculiar evolutionary history. So who are these elusive sharks? How did they end up like this? And why are they walking at all?
Whacky walkers
Despite recent discoveries the walking sharks are actually a group of animals that has been known to science for quite a while. It is only through a new paper by an international team of researchers that we are now learning more about this unique group. Their study has found 4 new species of walking or epaulette sharks since 2008 bringing the total to nine species all belonging to the genus Hemiscyllium. All nine species live in Australia, Papua New Guinea or eastern Indonesia and share lots of similarities in their anatomy, but vary greatly in skin colours and patterns. They all grow to around three feet in length and live on or around the seafloor either walking or swimming, which they can also do. They walk on their specially adapted pectoral and pelvic fins with a form of locomotion similar to that of a lizard. You can check out an epaulette shark taking a stroll for yourself in the video below.
Evolutionary edge
Although it looks pretty cool, it is hard to see why walking might have evolved in the epaulette sharks. Walking on your fins doesn’t seem any more advantageous underwater than swimming with them. However it soon becomes obvious as to why they do it at low tide. On the coral reefs and coastal shores where the epaulette sharks live a portion of the habitat becomes exposed at low tide, creating areas of isolated water known as tidal pools. Thanks to their unique behaviour and high tolerance to being out of water walking sharks are the only predator capable of moving between these pools. This means they can take their pick of the prey trapped in these areas who are unable to escape them. Lead researcher Christine Dudgeon from the University of Queensland told national geographic that this makes walking sharks “the top predator on the reef” during low tide.
Newest sharks on the planet?
In addition to discovering more species of walking shark and learning more about their unique behaviours, the study by Dudgeon and her colleagues was also important for another reason. By taking genetic samples from the newly discovered species and museum specimens they have shown that epaulette sharks are only around 9 million years old. This may sound like a long time but most shark species emerged well over 100 million years ago, with some species like the sixgill shark believed to be 180 million years old. During this time most species have barely changed at all due to their constant environment and long lives.
Speaking to national geographic Gavin Naylor, director of Shark Research at the University of Florida and fellow author on this paper, said “this may be the one place in the world where speciation is still going on for sharks”. It also means that epaulette sharks are likely to be the most recent shark species to have emerged in our oceans and therefore makes them very important for finding out why some sharks change over time and others do not. The researchers predict that their limited range, preference for certain reefs and constant tectonic activity in the region are the likely drivers in their relatively rapid evolution.
More to discover
These new discoveries prove just how much there is still left to learn about marine life in our oceans. Of the nine species of walking shark only four have enough data to be listed in the IUCN red list for conservation, meaning we are unsure if they are under threat or not. Who is to say that there aren’t even more species of epaulettes out there somewhere? As we continue to look deeper into our oceans the discoveries we will make will continue to delight us with such incredible and interesting creatures.
Marine Madness 