An international team of scientists, led by Dr. Brooke Flammang from New Jersey Institute of Technology, has identified unique anatomical features in a species of blind fish – the waterfall climbing cave fish (Cryptotora thamicola) — that enable the fish to walk and climb waterfalls in a manner comparable to terrestrial vertebrates.
The waterfall climbing cave fish (Cryptotora thamicola): dorsal view, resting on the bottom of glass tank. Image credit: Daphne Soares.
The waterfall climbing cave fish, also known as the cave angel fish, is a rare species of fish endemic to the Tham Maelana and Tham Susa karst formation in northern Thailand.
This fish can grow to 1.1 inches (2.8 cm). It is depigmented and has no visible eyes.
It can walk up rocks in fast-flowing water and on wet surfaces in air.
“Cryptotora are found only in rapids and not in lentic pools,” Dr. Flammang and co-authors wrote in a paper published in the journal Scientific Reports this week.
“They are commonly observed climbing steep rock surfaces in fast-flowing waterfalls created by basalt or andesite intrusions.”
“While it is anecdotally known that these fish can walk, the rare and protected status of these fish has limited research into the functional morphology of their walking behavior.”
According to the team, the waterfall climbing cave fish possesses morphological features that have previously only been attributed to tetrapods.
“We show that the blind cavefish Cryptotora thamicola walks and climbs waterfalls with a salamander-like diagonal-couplets lateral sequence gait and has evolved a robust pelvic girdle that shares morphological features associated with terrestrial vertebrates,” the scientists said.
“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,” Dr. Flammang added.
The discovery of this unique capability, not seen in any other living fishes, also has implications for understanding how the anatomy that all species need to walk on land evolved after the transition from finned to limbed appendages in the Devonian period (419.2 to 358.9 million years ago).
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Flammang, B.E. et al. 2016. Tetrapod-like pelvic girdle in a walking cavefish. Sci. Rep. 6, 23711; doi: 10.1038/srep23711
