The discovery of a small fish in Thailand may support the long-held belief by scientists that 400 million years ago the ancestors of modern-day land animals really did pull themselves out of the ocean and find a new home on land. Researchers from the New Jersey Institute of Technology (NJIT) found a blind cavefish that has the ability to walk on land and climb waterfalls in caves in the Tham Susa and Tham Maelana cave formations of northern Thailand. The creature has been found nowhere else on earth.
Cryptotora thamicola’s discovery was published on Thursday in the journal Nature Scientific Reports. Researchers saw the fish climbing rocks and waterfalls with the aid of salamander-like limbs that move in the same way as those on a four-footed mammal or amphibian. No other fish with these anatomical features has ever been found.
According to the study, although there have been many cases of secondarily aquatic vertebrates, there is fossil evidence of only a single period of time in which vertebrates emerged from the sea and began to walk. Finding the cavefish is significant as it represents the first example of morphological and behavioral adaptation in an existing creature that relates to walking behavior and morphology of tetrapods.
Although other “walking” fish have been found, those move with more of a hopping motion. Cryptotora thamicola uses its fins in a manner similar to a salamander, twisting the body from side to side and using the front and rear fins to take steps.
NJIT’s Brook Flammang said, “from an evolutionary perspective, this is a huge finding. This is one of the first fish that we have which is a living species, which acts in a way we think fish must have acted when they evolved from a fluid environment to a terrestrial environment at the very beginning of the fin-to-limb transition, when the first limbs evolved in our earliest ancestors.”
Due to its rarity the fish is difficult to study. Important questions still to be answered include how, given the lack of eyes, the fish find food and also how they find each other in order to mate.
Images from New Jersey Institute of Technology