Buzz
When you pause to consider it, you’ll realize there are quite a few animals that don’t possess eyes. Jellyfish, hydras, sea urchins, sea cucumbers, worms, and many other creatures never developed a way to see. Instead, they rely on different methods to explore their surroundings.
In addition to these animals, some evolved eyes at one point but later lost them, while others developed eyes that no longer serve their original purpose. Despite their blindness, these fascinating creatures have adapted in remarkable ways to survive and thrive in their environments.
10. Blind Legless Lizard – Dibamus Dalaiensis
A legless lizard species, discovered in Cambodia in 2011, is entirely blind, as its name suggests. While it shares some features with snakes, it belongs to the Dibamidae family of blind skinks. Unlike snakes, this lizard has external ears and, depending on its gender, may possess small bumps where legs would typically be. This discovery marked the first-ever finding of such an animal in Southeast Asia.
The Blind Legless Lizard of Cambodia has evolved to live without eyes, spending almost its entire life burrowing through the soil. As one researcher put it, 'Those adaptations are simply a waste of energy when you're working your way through underground tunnels.' Legless lizards predate snakes, and many of these creatures, including this newly discovered species, face threats. D. dalaiensis, as far as researchers know, exists only in a small area on a single mountain in Cambodia, which is under threat from logging and other industrial activities.
9. Brazilian Blind Characid – Stygichthys Typhlops
In the caves of Minas Gerais, Brazil, the Brazilian Blind Characid thrives. This species of cave-dwelling fish has evolved to live without eyes or pigmentation. These small fish, up to 1.8 inches (4.6 cm), lead solitary lives in their cave ponds. In the wild, they have become increasingly rare, mostly due to the declining local water table, which has caused many of their ponds and streams to dry up. Although their numbers are dwindling in the wild, they are sometimes kept in aquariums, where their distinctive features are highly valued.
Originally discovered in the 1960s, the Brazilian Blind Characid was rediscovered in the early 2000s. Since then, only a limited number of individuals have been studied both in their natural habitat and in laboratories, where researchers have observed their behavior. These fish do not react to light, and no eyes are visible where they would normally appear in other tetra species. Stygichthys typhlops is the last known species of its genus, and there was once a surface variant, but it is likely extinct due to habitat destruction. The Brazilian Blind Characid is confined to a 25 km-long aquifer and is threatened by further habitat loss from a sinking local water table.
8. Kentucky Cave Shrimp – Palaemonias Ganteri
The Kentucky Cave Shrimp is a freshwater species of troglobite shrimp found in the caves of Barren, Edmonson, Hart, and Warren Counties, Kentucky. This unique species has evolved without eyes, and its transparent, pigmentless shell makes it nearly invisible. The shrimp live exclusively in underground streams within caves, primarily within Mammoth Cave National Park. They thrive in this low-energy environment by feeding on sediment that washes into the cave from groundwater movement, which contains protozoans, fungi, algal cells, and other organic materials.
Unlike most shrimp species that have small eyestalks with ocular receptors, the Kentucky Cave Shrimp has no eyes and cannot detect light. This species resembles Ghost Shrimp, a common aquarium inhabitant, but unlike them, the Kentucky Cave Shrimp is endangered due to its limited range. It occupies only a small region in Kentucky, where its habitat is threatened by deteriorating water quality caused by groundwater contamination. Thankfully, conservation efforts are in place to protect this rare and unusual creature.
7. Olm – Proteus Anguinus
The Olm is a unique species of aquatic salamander and the only cave-dwelling chordate in Europe. Fully aquatic, it spends its entire life submerged in the caves of the Dinaric Alps, where it feeds, sleeps, and breeds underwater. Known for its fleshy skin, locals have dubbed it the 'human fish,' and it has a fascinating history dating back to 1689 when the first specimens were discovered after heavy rains. Once thought to be the offspring of a cave dragon, the Olm is simply a salamander and, unfortunately, cannot breathe fire.
Unlike some other species on this list, the Olm has eyes, but they are underdeveloped and incapable of perceiving light. It relies on its keen sense of smell and hearing to navigate the pitch-black environment of the caves. The eyes are mere slits covered by transparent skin, lacking both eyelids and visible sight functions. The Olm has small limbs, with three toes on its forelimbs and two on its hind feet, and its lack of pigmentation gives it a pale, earthworm-like appearance.
6. Kaua’i Cave Wolf Spider – Adelocosa Anops
The Kaua’i Cave Wolf Spider is a blind species native to a handful of caves in the Koloa–Po’ipu region on the Hawaiian island of Kaua’i, with only six known populations. It is relatively small for a wolf spider, measuring around 0.8″ (20 mm) in body length. Unlike its above-ground relatives, which have large eyes, the Kaua’i Cave Wolf Spider has lost its need for vision and has no eyes at all. This harmless spider preys mainly on a small amphipod, which is found only in this region and shares its limited habitat.
Due to the restricted range of the Kaua’i Cave Wolf Spider in the Koloa–Po’ipu caves, its habitat is under threat, primarily due to human activity. The introduction of chemical and biological pest controls, which eliminate the spider's food source, has resulted in significant declines in the population. With only a few known populations left, the Kaua’i Cave Wolf Spider is classified as endangered. Efforts are currently underway to preserve its habitat and mitigate further threats to ensure the spider's continued existence.
5. Widemouth Blindcat – Satan Eurystomus
The Widemouth Blindcat is a rare species of catfish found only in the artesian wells around San Antonio, Texas. As the sole species in the genus Satan, it was first discovered in a dark well, highlighting its adaptation to a lightless, underground environment. The fish lacks pigmentation, and true to its name, it has no visible eyes. Although its ancestors likely had eyes, the Widemouth Blindcat’s eye remnants are greatly reduced, with no discernible retina or lens. The optic tract remains, but it no longer connects to the brain, further emphasizing its reliance on other sensory adaptations for survival.
The Widemouth Blindcat is a smaller species of catfish, measuring around 5.4″ (13.7 cm) in length. Found with crustacean remains in their stomachs, these fish are clearly apex predators in their environment. However, groundwater contamination has led to their classification as vulnerable, and their population has been on the decline. Conservation efforts are in place, but the species faces significant challenges due to its limited distribution in a small region of central Texas.
4. Blind Albino Cave Crab – Munidopsis Polymorpha
The Blind Albino Cave Crab is a type of squat lobster, native only to the caves of Jameos del Agua in Lanzarote, Canary Islands. These small, pale, and completely blind creatures live exclusively in ancient lava tubes formed by volcanic eruptions thousands of years ago, when seawater flooded the caves. Despite being discovered in 1892, little is known about them, but they are an iconic symbol of Lanzarote.
The Blind Albino Cave Crab inhabits caves that are a popular tourist attraction in Lanzarote, listed on TripAdvisor as a must-see destination. These crabs, resembling tiny lobsters, lack pigmentation and eyestalks, and show no response to light. They navigate through their environment using their senses of smell, taste, and touch. Unlike many species on this list, they are not currently considered at risk by the International Union for Conservation of Nature.
3. Texas Blind Salamander – Eurycea Rathbuni
The Texas Blind Salamander is an extremely rare species of cave-dwelling amphibian, native only to the San Marcos Pool of the Edwards Aquifer in San Marcos, Texas. Reaching up to 5″ (13 cm) in length, this salamander survives by consuming whatever flows into its dark habitat, including blind shrimp, snails, and small fish. The species was first discovered in 1895 when it was found in a well drilled 58 meters below the surface. Since then, they have been studied at seven known locations around San Marcos.
Lacking eyes, the Texas Blind Salamander has only subdermal, sightless black spots where eyes would normally be. It hunts by sensing the slightest movement in the water, using side-to-side movements to detect changes in water pressure. Due to its limited range and groundwater pollution, this salamander has become increasingly rare. The International Union for Conservation of Nature (IUCN) has classified it as vulnerable, and conservation efforts are ongoing to safeguard its habitat.
2. Mexican Tetra – Astyanax Mexicanus
The Mexican Tetra is a species of characin found in the freshwaters of the Rio Grande, Nueces, and Pecos Rivers in Texas, as well as in various waters across central and eastern Mexico. These fish grow up to 4.7″ (12 cm), which is considered large for a tetra, and are characterized by their lack of pigmentation and eyes. Like the Brazilian Blind Cavefish, the Mexican Tetra is a favorite among aquarists, particularly for cave-style tanks that require minimal lighting.
Originally, Mexican Tetras had eyes, as their surface-dwelling relatives still do. However, over time, they lost them, likely due to the energy-saving advantages of being blind. A published study concluded that 'for young, developing fish, the energy cost of sight is 15 percent greater than if they were blind.' This is because of the energy-intensive needs of photoreceptive cells and neurons, which these fish no longer possess. To adapt, they feed on everything they come across, including both dead plants and animals.
1. Southern Cave Crayfish – Orconectes Australis
The Southern Cave Crayfish is an intriguing species, primarily due to its remarkable lifespan. This centenarian creature can live well beyond 100 years, with one recorded specimen reaching an impressive 176 years of age. While it resembles other crayfish, it is distinct for its lack of pigmentation, making it translucent. It also lacks eyes and any reaction to light. This crayfish species is found in the underground waters of caves in Alabama and Tennessee, where it is considered to be of least concern in terms of survival.
Growing to about 1.8″ in length, the Southern Cave Crayfish has evolved to navigate its dark environment without the need for vision. This is particularly advantageous, as the caves it inhabits are completely devoid of light. It feeds on small fish, insects, and any organic material that enters the cave via groundwater, such as sediment. Observations have shown that these crayfish cling to cave walls, banks, and submerged rocks, where they bury themselves beneath stones.
