Underwater Camera Captures a Fish Walking Backward for the First Time

A team of scientists filmed a shrimp-like fish walking both sideways and backward in first-ever footage of such behavior in a fish.

In a recent paper titled “Walking Fish” published in the journal Ocean-Land-Atmosphere Research, a team of scientists from Sun Yat-sen University and the Southern Marine Science and Engineering Guangdong Laboratory revealed how they used remotely operated and human-operated submersibles to film the fish in action across three areas of the South China Sea.

Researchers filmed a bizarre shrimp-like fish moving sideways across the seafloor like a crab and even moving backward in a motion that resembles “moonwalking.” The behavior is believed to be the first recorded example of this type of movement in a fish.

The species known Scalicus engyceros, an armored searobin found in the western Pacific Ocean, was first described by Albert Günther in 1872 and was already known for its unusual ability to “walk.” Researchers had previously predicted that the fish might also be capable of moving sideways and backward, but the behavior had never been observed until now.

The new footage confirms that searobins use their free pectoral-fin rays to move along the seafloor. These thick, stiffened fin rays allow the fish to scuttle across the bottom in a way that resembles the movements of shrimp. When threatened, the fish can also use the rays to make a sudden, jerky leap.

“These walking fish harbor far more novel behavioral and evolutionary adaptations than previously assumed,” Han Tian, primary author and a doctoral researcher in School of Marine Sciences at Sun Yat-sen University, says in a press release.

Tian adds: “The creature retains the pectoral fins, which have evolved into flat, round plates, improving balance during walking and swimming, while its shrimp-like fin rays and tail enable explosive, jerky shrimp-style leaps when threatened”

The scientists also point to the searobin’s unusually large eyes as another striking feature. Although the fish apparently could not see the approaching vehicle itself, the researchers’ footage shows that it did move its eyes in response to the vehicle’s beam of light. This suggests that the searobin’s eyes retain some sensitivity to light, which may reflect how its visual system has adapted over the course of its life cycle.

Recent advances in deep-sea exploration technology, including human-occupied vehicles (HOVs) and remotely operated vehicles (ROVs), have given scientists new opportunities to observe animals in their natural environment. According to a report by ScienceAlert, researchers filmed the searobin at depths of 1,148 and 1,640 feet using the human-occupied vehicle Shenhaiyongshi, meaning “deep-sea warrior,” and the remotely operated vehicle Haiqin.

“Deep sea life remains mysterious today with so many unknowns. Modern deep-sea diving vehicles allow not only discovery of new species but also add a new in situ, functional dimension to the study of species based solely on the morphology of preserved specimens,” Tian says. “By observing deep sea animals alive in their surrounding environment, we can gain insight into the adaptation and evolution of the species.”