Humans are both blind and deaf and are deaf to natural law

When blind, hearing organs often develop better. But this is not true for Mexican blind fish or subtropical American fish.

After many generations living in the dark, many animals such as shrimp, fish, flatworms . have lost their sight. But apparently, there are some species, in addition to losing their sight, their hearing also has problems.

'We were quite surprised to find that some blind fish species have a slight hearing problem. They take a while to understand what's going on around them, ' said Daphne Soares, a sensory neuroscientist at the University of Maryland.

Soares and colleagues studied Amblyopsidae , a freshwater fish that lives mainly in the Eastern and Central American regions. They compared the hearing ability of two amblyopsid fish species, Typhlichthys subterraneus and Amblyopsis spelaea, to Forbesichthys agassizii , living in the water area, their closest relatives.

Cave fish go against the natural law: both blind and deaf.

When testing the species' ability to react to sound, the scientists found that all three species could hear the same sound at low frequencies, but only the water-based fish were available. Audio can be heard at higher frequencies, from 800Hz to 2kHz. They also found that the cave fish has the number of 'hairy' cells, responsible for sensing the sound in the ears, needed to hear, less than the species living on the water.

The reason why these fishes are 'deaf' is explained by scientists because the sound frequencies where they live rarely exceed 1kHz, so they only adapt to those frequencies.

'To compensate, these two fishes use their super-sensitive abilities with the impulse of water waves to find food and partners,' said Soares.