Thailand's blind, walking cavefish can ascend waterfalls

NEWARK, N.J., March 24 (UPI) -- A team of New Jersey scientists recently returned from a trip to Thailand where they discovered a fish unlike any other -- a blind fish that walks and climbs waterfalls, more like a four-legged amphibian than a fish.

Scientists say Thailand's cavefish, Cryptotora thamicola, is the only living fish species with such a developed gait. Their discovery is described in a new paper, published this week in the journal Scientific Reports.

Some other fish species have evolved the ability to use fins in a limb-like manner -- squirming across mud or pushing off from coral. But scientists say the cavefish is much more advanced; it's in a different category.

Thailand's cavefish doesn't squirm or flop disjointedly.

"These guys seemed to be very leisurely walking up the rock face," lead study author Brooke Flammang, an assistant professor of biology at the New Jersey Institute, told The New York Times.

"It possesses morphological features that have previously only been attributed to tetrapods," Flammang said in a news release. "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."

Tetrapods are a superclass of four-limbed vertebrates that includes groups of amphibians, reptiles, mammals and birds. The superclass also includes extinct fish species.

Evolutionary biologists believe ancient intermediate fish species were the first tetrapods, adapting four limbs for walking as they transitioned from the sea to the land. Researchers believe early tetrapods walked much like salamanders.

"This research gives us insight into the plasticity of the fish body plan and the convergent morphological features that were seen in the evolution of tetrapods," Flammang said.