What’s so great about having eyes anyway? If these eyeless animals could talk, they’d tell you that vision is overrated. Each one of these ten incredible creatures has an amazing story to tell. In the darkest environments, with nothing to go on but smell, touch and hearing, they manage to feed and reproduce, like blind super-beings with heightened remaining senses. Here’s a look at ten amazing animals without eyes.
10. Kauai cave wolf spider (Adelocosa anops)
Loads of people don’t like spiders. In fact, arachnophobia is among the most frequently experienced fears in the world, thought to affect as many as one in two women and one in ten men. Still, like a lot of other spiders that people are afraid of, the Kauai cave wolf spider (Adelocosa anops) is not dangerous to humans. What makes this spider particularly easy to identify is the fact that it has no eyes, differentiating it from other wolf spiders. Nicknamed “the blind spider” by locals, the species is very rare and endangered and can only be found in a small selection of caves in the Kōloa–Poʻipū region on the Hawaiian island of Kauai. The spider is a tiny 0.8 inches in length and mostly feeds on a type of cave amphipod. Why is the Kauai cave wolf spider so special (ignoring, for a moment, its exotic-sounding name)? Well, instead of using a web to catch its prey, it runs after its victims and seizes them with its triad of big teeth. Yikes!
9. Southern cave crayfish (Orconectes australis)
The southern cave crayfish (Orconectes australis) is a crustacean that lurks in subterranean freshwater systems around Alabama and Tennessee. Its body measures 1.8 inches in length, and what it lacks in eyesight it more than makes up for with touch and smell. Using these heightened senses, the southern cave crayfish navigates its way around its dark watery environment with ease, eating insects and fish. In its habitat, the species is said to favour walls, banks and open water in lieu of burying itself beneath rocks. And as with a lot of species that live in caves, its body is see-through. Scientists are particularly interested in the southern cave crayfish owing to its excessively long life span, which reportedly has been known to stretch for longer than 176 years.
8. Mexican tetra (Astyanax mexicanus)
You guessed it, the Mexican tetra (Astyanax mexicanus) is mainly found in Mexico, although it does live in Texas and New Mexico as well. This freshwater fish totally lacks pigmentation, which makes it an albino. As it doesn’t have eyes, it uses its “lateral line” sense organs and water pressure to detect movement. Although the fish can be found in an array of different habitats, it prefers to dwell in caves and pools with sandy, rocky bottoms. It is a small fish, measuring just 4.7 inches in length - which is ironic, because it will eat just about anything it can wrap its mouth around. There are a number of theories as to why the Mexican tetra doesn’t grow any eyes. According to some research, the fish does start to grow eyes as an embryo, but something halts their full development and, ultimately, flesh covers them. [Video]
7. Blind legless lizard (Dibamus dalaiensis)
You’re probably asking, “How can this be a lizard if it doesn’t have any legs?” Well, smarty pants, there are over 200 lizard species in the world without legs. In May 2011 the blind legless lizard (Dibamus dalaiensis) was discovered in Cambodia’s Cardamom Mountains. Although more research is still being done on the species, it is believed to exist underground and is said to have a sharp sense of smell, which leads it to its food. The blind legless lizard measures 6 inches in length, and its diet is thought to consist of worms, termites and ants.
Very little is known about the wildlife in the region this lizard inhabits because communist group the Khmer Rouge controlled the country between 1975 and 1979 and then operated as a guerrilla front that lasted until 1998; hence, researchers were not allowed access to the mountains. In a 2011 interview with National Geographic, conservation biologist Jenny Daltry said, “The first survey of animal life wasn’t until ten years ago and [Herpetologist Neang Thy of Fauna & Flora International] keeps coming back with amazing new discoveries.”
6. Texas blind salamander (Eurycea rathbuni)
The Texas blind salamander (Eurycea rathbuni) exists in total darkness in the caves of the Edwards Aquifer close to San Marcos in Hays County, Texas. This amphibian measures 5 inches long as an adult and has red gills that it uses to draw oxygen from the water. Its diet can alter depending on what turns up in its habitat, but small invertebrates are usually on the menu. When hunting, the species moves its head in a side-to-side motion to sense the waves and vibrations created by its would-be victims. Unfortunately, the salamanders are endangered, and a spring in the caves makes their situation even worse. The water can force them out of their environment and into the surrounding rivers, where catfish frequently gobble them up.
In 2005 a new net-capped pipe was installed to trap the salamanders when they were ejected. Once caught, they are transported to their new home at the U.S. Fish and Wildlife Service’s San Marcos National Fish Hatchery and Technological Centre, where they become involved in a breeding program. And this is a good thing given that, as service biologist Carrie Thompson points out, “We still have a lot to learn from these little guys.” [Video]
5. Widemouth blindcat (Satan eurystomus)
The widemouth blindcat (Satan eurystomus) is an albino freshwater catfish with no externally visible eyes. Although research shows that the species does have a visual system or optic tract, it never quite reaches the fish’s brain. Unique to Texas, the widemouth blindcat is mostly found in dark, underground areas of the Edwards Aquifer in San Antonio, and it will eat just about anything it can catch. The blindcat has a responsive lateral line (for sensing motion from vibrations) that apparently helps it to seek food, and it is thought to be a top predator in its habitat. Currently listed as vulnerable, the widemouth blindcat is susceptible to groundwater pollution. It is the sole species of the Satan genus and can grow to 5.5 inches in length.
4. Freshwater hydra (Hydra magnipapillata)
This freshwater hydra (Hydra magnipapillata)) uses its stinging tentacles to catch its prey as well as for self-defense, and while it doesn’t have eyes, the stinging cells in its tentacles react to light. The hydra usually preys on small crustaceans like water fleas, which it eats alive, just after it has captured them with its tentacles. Not impressed yet? Well, the 0.39-inch long creature has approximately the same quantity of genes as we do, and it has been documented as biologically immortal in that it effectively does not age. What’s more, although the species has been considered a pest in aquariums, it has also been a major resource in studies relating to both Huntington’s and Alzheimer’s disease. [More]
3. Blind albino cave crab (Munidopsis polymorpha)
Despite being referred to as the blind albino cave crab (Munidopsis polymorpha), this species is actually a squat lobster. Still, other than that misleading issue, the name pretty much sums up a lot of what is known about the elusive species. It is only found in the dark caves of Jameos del Agua in Lanzarote, one of the Canary Islands. Blind albino cave crabs are mysterious little creatures that definitely need to be researched further so that we can develop a better understanding of them. Even those most familiar with them in the area confess that they have never encountered any of the species’ eggs and haven’t even seen the crustaceans eat. Interestingly, no dead individuals have been found either. A squat lobster that’s blind, albino and resembles a crab? Now that is pretty unbelievable.
2. Brazilian blind characid (Stygichthys typhlops)
This unusual little fish - the Brazilian blind characid (Stygichthys typhlops) - was rediscovered in 2010, having previously only been known about from one individual specimen that was found almost half a century earlier. It exists in caves in the Brazilian state of Minas Gerais and thanks to its subterranean way of life, it has no eyes it can see with and there is no pigment in its skin. “This species seems to be the most threatened underground fish species in Brazil,” said ichthyologist Dr. Cristiano Moreira. Why? Because too much water is being withdrawn from the 15-mile long underground “aquifer” to which it is restricted. Little is known about its lifestyle or diet. What we do know, however, is that it is the only representative of its genus and, according to Moreira, that it may be the last existing member of an extinct group.
1. Olm (Proteus anguinus)
The olm (Proteus anguinus) is the only species of chordate in Europe that is specifically adapted to a cave environment. Unlike other amphibians, it sleeps, feeds and reproduces underwater. It can grow to up to a foot in length and eats snails, insects and little crabs. Like a lot of other species on this list, its skin doesn’t have any pigmentation. As the species dwells in dark caves and is blind, its other senses have become heightened. The olm’s head is equipped with highly sensitive receptors that can detect chemicals and movement. Researchers have also discovered new electroreceptor sensory organs on its head that have been called ampullary organs. The olm looks like something you wouldn’t want to stumble (or swim) upon. Back in 1689, naturalist Johann Weikhard von Valvasor noted that following intense downpours, olms were forced to the surface, prompting natives to think that they’d seen baby cave dragons. [More] [Video]
Bonus: Star-Nosed Mole (Condylura cristata)
The star-nosed mole (Condylura cristata) is mostly found in eastern Canada and in the northeastern part of the United States, where it lives underground. As a species, Condylura cristata is simple to identify thanks to 22 appendages that protrude from around its nose. Within those tentacles are 25,000 tiny sensory organs called Eimer’s organs, and these are so sensitive that they can detect energy waves that move through our planet’s layers. The star-nosed mole can reach 7.9 inches in length and feeds on small invertebrates, amphibians and fish. This amazing animal is also a great swimmer and can even detect smells underwater by blowing bubbles and then breathing them back in so that it can process the scents.
Research by neuroscientist and star-nosed mole expert Kenneth Catania showed that the mole’s nose would make very rapid movements similar in speed to super-quick “saccadic” eye movements whenever it found food. Catania described the moles as “a gold mine for discoveries about brains and behaviour in general - and an unending source of surprises." Not bad for a blind animal. [Videos]
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