Although the waterfall-climbing fish was discovered back in 1985, deep inside a system of caves in northern Thailand, little analysis had been done on it, since the species is protected, and can’t be removed from its habitat.
But, according to nytimes.com, Apinun Suvarnaraksha, a biologist at Maejo University in Thailand, and Daphne Soares, of the New Jersey Institute of Technology, observed the fish on a recent expedition to the caves and recorded a video of the fish in motion. Upon returning to the US, Dr. Soares played the video for her colleague, Brooke E. Flammang, a biomehanics expert, and she was “completely blown away.”
Instead of seeing the normal flopping around you would expect from a fish on the ground, the cave fish “seemed to be very leisurely walking up the rock face,” according to Dr. Flammang.
Since they could not get any of the fish from the caves for study, Dr. Suvarnaraksha found a preserved specimen in a museum in Thailand, which he took to a dental school and made images of the fish, using a high-resolution CT scanner.
He sent the images to Dr. Flammang and she was able to pair up the pictures to make a 3D model anatomy of the cave fish. That model revealed the fish had a pelvis similar to a tetrapod, in that it was fused to the spine by elongated ribs, the same bone alignment that allows tetrapods to lift themselves up on their hind legs.
Subsequent videos taken by Dr. Suvarnaraksha in the caves, using a video camera to capture the movements of the fish in an aquarium, confirmed the initial theories by Flammang and her colleagues. The cave fish were using their bodies in the same fashion as the salamander, walking in a tetrapod-like manner.
Dr. Flammang said, “Functionally, it makes perfect sense, but to see it in a fish is incredibly wild.” She adds these fish may eventually give scientists hints about how fish originally arrived on the land.
The research team published their findings in the journal Scientific Reports.