We think of fish as skilled swimmers, but in reality, they have evolved the ability to “walk” at least 5 times.
An international group of researchers from Australia, the United States, and Indonesia has discovered species of fish that use their fins to walk and are gradually evolving to adapt to life on land.
Some fish pull themselves forward and use well-developed front fins to walk, while others “walk” by using their fins along the ocean floor.
Walking Fish Species
However, the evolution of walking in fish is still limited. Today, there are over 30,000 fish species, of which only more than 10 can “walk,” according to The Conversation.
Sarcopterygian fish, also known as lobe-finned fish, can walk like humans. Lobe-finned fish differ from other fish in several important ways. For instance, their fins (limbs) have supportive bones and muscular lobes that allow them to move on land.
We do not yet know the ancestors of this species, but they likely resembled a type of fish called Coelacanth, which has many fossils and is often referred to as a “living fossil,” currently residing in the Western Indian Ocean and Indonesia.
3D rendering of the extinct Tiktaalik fish – (Image: SHUTTERSTOCK)
An example of a walking living fossil fish is the mudskipper (family Oxudercidae). These fish inhabit marshes and tidal flats and use their pectoral fins to walk on land.
These fins help them escape from underwater predators, forage for food (they consume organic matter in the mud), and even interact on land by finding mates.
Another walking fish is the walking catfish (Clarias batrachus), which uses its pectoral fins to move on land, helping it escape from drying ponds and seek new habitats.
A recent study published in the journal Marine and Freshwater Research reveals that scientists in Australia, the United States, and Indonesia have discovered four species of sharks evolving the ability to walk on land.
These sharks use their fins to move like four legs. Although they primarily live underwater, they can sometimes be seen wading among coral reefs or even climbing onto land to move from one puddle to another.
Which Genes Help Fish “Walk”?
Little skate (Leucoraja erinacea) is a species of cartilaginous fish related to rays and sharks. It is a fish that “walks” underwater using its fin-like limbs, mimicking the movements of land-dwelling animals.
Little skates are favored by scientists for research on the evolution of locomotion because they have independently evolved a way to walk using their fins. However, the genetics behind walking in little skates is challenging to study due to a lack of quality data.
Recently, this has changed as researchers from Seoul and New York used advanced technology to construct a high-quality gene set for the little skate.
Scientists found that it only uses 10 muscles to move its fins, while four-legged animals typically use 50 muscles to move their limbs.
A major question regarding the evolutionary process of vertebrates is: Which genes are crucial for developing the muscles necessary for locomotion?
To find the answer, the research team examined which genes are active in the nerves controlling the limbs (motor nerves) in mice, chickens, and little skates.
They discovered similar gene expression patterns in the motor nerves that facilitate these muscles’ movement.
Thus, walking fish may have undergone various evolutionary paths, but recent research suggests they share a common genetic mechanism.
