The cavefish Cryptotora thamicola is blind as a – well, blind as a cavefish. But according to a study published Thursday in Scientific Reports, the fish uses a unique method of movement that allows it to walk like a four-legged animal. In fact, it can even climb its way up a waterfall.
"It possesses morphological features that have previously only been attributed to tetrapods," or four-footed mammals and amphibians, study co-author Brooke E. Flammang of the New Jersey Institute of Technology said in a statement. "The pelvis and vertebral column of this fish allow it to support its body weight against gravity and provide large sites for muscle attachment for walking."
When Flammang first saw the pink fish in footage taken by co-author Daphne Soares, she was blown away by its salamander-esque wiggle. There are other fish that use their fins in feetlike ways, but Cryptotora thamicola takes the skill to new heights.
“I was like, ‘Fish can’t do that,’” Flammang told Wired. “That’s ridiculous.”
Plunged into complete darkness inside caves in Thailand, the fish stick fast to the rock behind flowing waterfalls and climb their way to the top. That's unusual, as the researchers explain in the above video, because they wouldn't expect eyeless fish to be able to function so well in fast-flowing water.
Scientists think the ancestors of land animals must have moved in similar ways when they first dragged themselves out of the sea.
“From an evolutionary perspective, this is a huge finding,” Flammang told Discovery News. “This is one of the first fish that we have as a living species that acts in a way that we think they must have acted when they evolved from a fluid environment to a terrestrial environment.”