Walking fish may sound outrageous to most people, but these creatures are real! In 2016, researchers from the New Jersey Institute of Technology (NJIT) had discovered a rare species of fish that can walk underwater. This walking fish is known as the Cryptotora thamicola, which lives in the caves of Thailand, and they do not have any eyes.
The researchers also noted that the cave angelfish swim in flowing water and uses their fins to walk and climb on the stones inside the cave.
Four years later, some researchers discovered that there are 11 species of fish with the same ability, not to mention the walking shark found in Australia earlier this year. Using a CT scan, the team was able to analyze the pelvic structures of the fish species and confirmed they could also walk like the cave angelfish.
According to their findings, these 11 walking fish have a more robust sacral rib connection that supports the fins and the spinal column, which allows them to walk on land with a tetrapod-like lateral sequence.
11 New Species of Walking Fish
Researchers from the New Jersey Institute of Technology, Florida Museum of Natural History, Louisiana State University, and Maejo University in Thailand discovered 11 new species of a walking fish.
Florida Museum's imaging lab manager and study author Zachary Randall said that the concept of cave angelfish was unique when it was first discovered. He added that fishes do not typically have a connection between their spine and pelvic, but they were able to find these connections in 11 species of fish, making walking fish more common than previously thought.
According to the researchers, the salamander-like gait of the cave angelfish has made it a unique species. But it is not the only fish that can climb as the Hawaiian waterfall climbing gobies can also do that using undulation or suction to move out of the water.
On the other hand, cave angel fish walks with a 'diagonal-couplets lateral sequence,' a behavior only attributed to tetrapods. It belongs to the hillstream loach family that lives throughout Southeast Asia, but it is the only one who can walk.
"The modified morphology of these Balitoridae, particularly the enlarged sacral rib connecting the pelvic plate to the vertebral column, is a big part of why studying this family is so exciting," says study corresponding author Callie Crawford who is a Ph.D. candidate at the Department of Biological Science in NJIT.
Read Also: New Species of "Walking" Sharks Found in Australia
Moreover, she said that the structures of these loaches have developed to accommodate the walking requirements needed for them to walk on land.
They were able to discover three anatomical groupings of this species, which has significant implications for the biomechanics of walking on land by these loaches. The relationship among the fishes and their structural capacity to walk on land suggest that their ability to walk on fast-flowing rivers could be passed on to the next generations rather than their specific morphology.
Three Anatomical Groupings of Loaches
The hillstream loach fish has over a hundred species. The study discovered that there are three variations of pelvic structure in the 29 species they studied.
One group has a narrow and long rib which connects to the pelvic rib, while the second variation of the group has a thicker, slightly curved rib that meets the pelvic plate. In contrast, the last group had a robust crest rib, which connects with the pelvic plate of the fish.
However, only 11 out of these 29 species belong to the third category, which is similar to what previous researchers have found in the cave angelfish that provides them the ability to walk.
Read More: 16 Species of Ultra-Black Fish Goes Invisible in the Ocean's Dim Backdrop
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