The oceans of the world have been home to the planet’s shark population for millions of years. For the most part, shark species have not changed much in that time. But there are shark species that have uniquely evolved when compared to their aquatic brethren.
Some of these sharks have even learned to walk on land. Can you imagine that?
Sharks Take to Their Feet
These walking shark species are approximately three feet long, and many of them are native to Australia.
The walking sharks, also called Epaulette sharks, use their pelvic and pectoral fins to walk both along the seafloor. They’ve been seen walking on land when the tide is low. This never before seen mobility among the shark species allows the walking shark to maneuver among the reef and tide pools that exist in their natural habitat. Furthermore, it gives them a leg up on the competition when hunting small fish, crabs, shrimp, and other food targets.
Observing Walking Sharks
Christine Dudgeon is a researcher at Brisbane, Australia’s University of Queensland. Dudgeon explains that the ability to walk makes the walking shark a formidable predator.
A study followed the progress of the walking shark for several years. According to the organization, four new species of walking sharks have been identified over the last 12 years. This brings up the total known species of walking sharks to nine.
Additionally, a recent article from the journal of Marine and Freshwater Research pointed out that all of these walking shark species have evolved from previous shark species over the last nine million years.
Gavin Naylor is another shark researcher who works out of the University of Florida’s Florida Program for Shark Research. Naylor says most shark species evolve slowly and explains that what is being witnessed with the walking shark is highly unusual. Naylor pointed to the Sixgill shark as an example of a species that has evolved so slowly the species seems to be trapped in prehistoric times. Naylor says it is not uncommon to see shark species sport teeth identical to the teeth that members of the species possessed well over 100 million years ago.
Meanwhile, the walking shark is presently evolving in their natural habitats in Australia, the eastern portion of Indonesia, and Papua New Guinea.
It Began Long Ago
Scientists explain that the ancestors of today’s sharks and other jawed vertebrates began to separate about 400 million years ago. The number of shark and ray species identified at that time is about 1,200. Naylor says that historically these animals have proven to be slow at reproducing and evolving but possess long lifespans.
In most cases, this combination of traits would make the long-term survival of a species difficult. This is because the ability to adapt to the changing conditions of its environment is necessary for a species to avoid extinction.
Naylor says that conventional scientific logic fails to explain why sharks are not extinct, leaving many scientists questioning why they aren’t.
The reality is that sharks have not simply faded away into extinction. They’ve also been able to outlast other animal species that have shared the oceans with them. Despite the ocean’s ever-changing conditions, sharks have figured out a way to survive and thrive.
Newly Discovered Walkers
Scientists had only identified five species of walking sharks by 2008. These aquatic animals are marked by different colors and body patterns but possess similar anatomies. However, recent studies that have been completed in more detail than previous studies demonstrated there are actually nine species of walking sharks. The study also showed precisely at what point in their history each species diverged from parent species.
Dudgeon was joined in the study by a group that included Gerry Allen of the Western Australian Museum and Mark Erdmann of Conservation International. The group was able to gather DNA samples by taking tiny fin parts from the sharks without causing the animals any physical discomfort. The group also made use of DNA samples from museums
The gathered samples were then sent to Naylor’s lab to be sequenced and analyzed. A comparison was conducted that resulted in a complete genetic analysis of the walking shark.
The walking shark faces the same threat of fishing and harvesting that plagues other aquatic species. A few of these species are also restricted to a small area of the world, further increasing their vulnerability.
Add in the fact that only three walking sharks species are listed on Nature’s Red List of Threatened Species maintained by the International Union for Conservation, and it would be easy to assume that walking shark species are in trouble. Despite this fact, no walking shark species is thought to be endangered or seriously threatened by extinction. And science can only wonder at what evolution will next bring for the walking shark.