Buzz
Certain species have become so specialized to life in subterranean caverns that they've lost their color and vision, yet gained incredible adaptations to survive in total darkness. These creatures, known as troglobites, are often so rare that much of their behavior remains a mystery to us.
10. Enigmatic Cave Leeches
Exclusively found in Croatia’s Mt. Velebit, Croatobranchus mestrovi is an extraordinary leech species that resides in frigid water pools at the base of deep shafts. These completely white creatures feature unusual leglike appendages along their bodies and five small, finger-like tentacles around their mouths. The purpose of these tentacles is still unclear, and little else is known about this creature's behavior or habitat.
While leeches are most commonly associated with bloodsucking, other species hunt snails, worms, or scavenge decomposing matter. However, the diet of this particular species remains a mystery, as few organisms share its icy habitat.
9. The First 'Official' Cave Insect
Not long ago, the existence of cave life was an enigma. Many scientists believed that no organism could thrive entirely within cave ecosystems and assumed that any creatures found there had simply wandered in from the outside.
This perception shifted when a single beetle, Leptodirus hochenwartii, was officially documented in 1831. The discovery of this pale, sightless, long-necked scavenger, fully adapted to cave life, marked the dawn of speleobiology—the study of cave ecosystems—as a distinct scientific field.
8. The Barbel Fishes
The Latin name Sinocyclocheilus translates to “crossed-fork back,” though this might overlook one of the genus's most striking features—a skull that seems almost “sunken in” or “collapsed.”
This genus contains species ranging from fully sighted surface dwellers to semi-subterranean fish with small, weak eyes, and even true troglobites, completely blind and lacking pigmentation. Their diversity makes them a prime subject for evolutionary studies, showcasing how fish trapped underground can rapidly evolve into troglobitic forms.
7. The Blind Hunting Spider
While many spider species are known to inhabit caves, the discovery of true troglobitic hunting spiders—such as wolf spiders—didn't occur until 2012. That year, the species Sinopodia scurion was found in a cave in Laos.
The pale, transparent scurion stands out as the only completely blind species among over 1,000 known huntsman spiders. Like the barbel fishes, this species has relatives that retain their sight, ranging from a single, weak pair of eyes to the full set of eight, typically found in species closer to cave entrances or in open environments.
6. Lava Tube Crabs
Munidopsis polymorpha isn't truly a 'crab' but a crab-like 'squat lobster' found solely in a lava tube beneath the Canary Islands, which holds the record as the longest lava tube ever discovered. Interestingly, these creatures feed entirely on microscopic, photosynthetic diatoms, which depend on sunlight to thrive.
The diatoms that sustain the crabs are illuminated by sunlight filtering through just two small openings in the cave’s ceiling. The blind crustaceans feed in the dimness near these rare pools of light. Polymorpha was originally discovered as a fossil and was thought to be extinct until it was rediscovered.
5. The Blind Cave ‘Piranha’
Stygichthys typhlops may be one of the most intimidating-looking troglobitic fish, with its large head and menacing underbite filled with sharp teeth. As a type of tetra, it shares some evolutionary history with the notorious piranha.
A single specimen of this fish was discovered in a well in Brazil during the 1960s. After no more individuals were found for over 50 years, it was feared they had gone extinct. However, in 2010, several more specimens were located, although their survival may now be threatened by decreasing water levels in their underground habitat.
4. The Blind Worm Lizard
Amphisbaena caeca is the only animal on our list that doesn’t actually reside in caves. Nevertheless, it spends such a significant portion of its life underground that it has developed similar adaptations to cave-dwelling species.
With no pigmentation, its translucent body gives it a pinkish, earthworm-like appearance. Its small eyes are hidden beneath the skin, capable only of detecting light and dark. These legless reptiles are mainly found in Puerto Rico and feed primarily on termites or the soft eggs and larvae of ants.
3. The Spider-Hunting Labyrinth Bug
Phasmatocoris labyrinthicus is the only creature on our list with relatively good eyesight, which is essential for it to fly and locate new caves in search of a mate. As a true bug from the Hemiptera order, it possesses a beak-like mouthpart, which it uses to inject paralyzing venom into its prey and suck out their liquefied insides.
This secretive insect will consume nearly anything it can capture, though its primary diet consists of spiders. It has special bristles on its front legs designed for manipulating spiders’ webs. Incredibly, adult labyrinth bugs have been seen holding onto old, abandoned webs and stretching them tight, possibly 'reclaiming' the empty webs for their own purposes.
2. Cave-Dwelling Planthoppers
For many years, it was thought that tropical ecosystems typically didn’t support caves with endemic life. In fact, very few troglobites were known in Australia until the 1980s, when Bayliss Cave was discovered to harbor an astounding variety of troglobitic insects, arachnids, millipedes, and other invertebrates.
One of the most unexpected discoveries was the presence of troglobitic planthoppers, insects closely related to cicadas and typically found in grasslands and forests. It’s surprising that such a plant-dependent insect could fully adapt to cave life, yet these tiny creatures thrive on the sap they extract from plants and tree roots that have made their way into the dark, subterranean world.
1. The Texas Blind Salamanders
We’ve previously discussed the olm, a well-known species of troglobitic amphibian. However, other salamander species have also evolved to live in underground habitats, including two species found in Texas.
The eyeless Eurycea rathbuni is the more specialized and more frequently encountered of the two species, though it remains a rare organism, reliant on water from a single primary aquifer. Even rarer is Eurycea waterlooensis, which has minuscule eyes and can only be found in water-filled cavities deep beneath the floor of Barton Springs in Austin.
Similar to the olm, axolotls, and a few other salamanders, these creatures display neoteny, retaining their juvenile gills throughout their adult life.
