When it comes to evolution, anything that doesn’t serve the animal in surviving its immediate environment becomes atrophied over time. This can be seen in animals that live in places with little to zero access to light; living in such conditions means that their eyes are now totally useless and unnecessary organs. In this article, we’ve highlighted some of the most unique and fascinating subterranean creatures that found a way to keep on thriving in their cold, dark homes. 

1. Blind Spider

One of the well-known facts surrounding spiders is that they possess eight legs and anywhere between two and eight legs. However, very few people are aware of certain species of spiders that have none at all! That’s because they were discovered only fairly recently in 2012 by scientist Peter Jäger, 60 miles from the enormous Xe Bang Fai river cave in Laos. So far, only 1,100 of these giant huntsman spiders have been accounted for, and their translucent body and heightened senses are a clear indication of their gloomy lifestyle.

2. Texas Blind Salamander

As with any animal that lives in near or total darkness, the Texas blind salamander is a spooky fellow with a pale white appearance, two tiny spots under the skin where their eyes used to be and extended gills along its neck to allow for underwater breathing during the adult phase. These salamanders are reasonably sized, measuring up to 5.5 inches long and can only be found in a system of caves full of water from the Edward Aquifer in Hays County, Texas. Their remaining senses are top notch, with the salamander being able to tell when its potential dinner is lurking nearby.

3. Mexican Tetra

Appearance-wise, the Mexican Tetra, also known as the blind cavefish or Astyanax mexicanus, appears no different than other tetra fishes save for the fact that you can see its bones and internal organs. And no, it’s not its own separate species, just a variant of the Mexican tetra that have adapted over time in order to navigate the dim underwater caves. Juveniles do in fact possess some light sensing ability, but this trait does not stick around in adulthood as it is more convenient for the fish to navigate its environment via water pressure fluctuation sensing.

4. Blind Deep Sea Lobster

The blind deep sea lobster looks absolutely nothing like its sighted cousins—that bright-orange pigmented shell is now replaced by a ghostly one with only a hint of color remaining at the tip of its tails, appendages and head. Since their discovery in 1880, the blind deep sea lobster has only been documented in the depths of the Philippine Sea, some 984 meters below. Its claws are another unusual feature; they are so disproportionate that the longer claw is nearly the length of the lobster’s entire body.

5. Blind Cave Crayfish

Another contender for the most exceptional eyeless animal is none other than the blind cave crayfish, a close relative of lobsters. And, like the other creatures on this list, the blind cave crayfish appears to be nothing more than a ghastly apparition of its regular cousins. The blind cave crayfish first caught the attention of the scientific community back in August 16, 1999 in muddy, flooded caves in Ozark County, Missouri where they feed on equally blind prey including the blind cave salamander.