The olm, a troglobite

To see life on another planet, most would suggest a radio telescope or a NASA explorer vehicle. Yet immediately below the earth’s surface there exists an otherworldly ecosystem populated by creatures that never see the light of day. These animals are the troglobites — crustaceans, amphibians, insects and more — built to survive in the dark, limestone labyrinths that form most of the world’s cave systems.

A pseudoscorpion that doesn’t have a stinging tail and instead injects venom with its claws. A Nelson cave spider with claws on two of its super-long legs that measure just shy of six inches. A whitish, almost transparent cave crayfish that can live over 150 years. These are just some of the troglobites, many of which possess similar evolutionary adaptations: blindness, long limbs and spiky feet to better navigate rocky terrain, and lack of pigmentation as there is no need for camouflage in the dark.

Of all the troglobites, it is perhaps the proteus anguinus, or the olm, that is the star. In Slovenia, a tourism industry exists for those who desire a glimpse of the ghostly salamander that’s beguiled humans for hundreds of years. The first written account of the olm dates back to 1689, in which scholar Janez Vajkard Valvasor disputed the belief that olms were baby dragons. Found in the Dinaric Karst of Europe, it’s easy to see why olms could be fodder for myth. They are blind, yet have barely visible, regressed eyes covered by skin. Their serpentine body can grow over a foot in length, and is covered by whitish, translucent skin that’s artfully highlighted by two frilly pink gills at the back of its head. And, unlike other amphibians that metamorphose into an adult form, the olm retains its larval features, a phenomenon known as neotony. Olms spend their whole lives in water, and so there is no need for them to develop terrestrial characteristics.

In keeping with this fairytale-like appearance, olms are said to be able to live up to 100 years and can go without eating for several. Yes, several years. They, like many troglobites, have exceptionally slow metabolism in large part because of the dearth, or erratic availability, of food. Like other troglobites, the olm compensates for lack of vision by using other, specialized senses. Olms’ ears are capable of receiving sound waves in water and vibrations from the ground, their sense of smell is keener than that of most amphibians, and they possess sensors in their heads called “ampullary organs” that enable them to detect weak electric fields.

Despite such specialized capabilities, troglobites are critically connected to what’s going on above earth’s surface. For a nutritious banquet, some troglobites feast on piles of bat guano found on cave grounds. Tree roots that grow through cracks in a cave’s ceiling and leaves that flow in with water can also provide nutrition. But this water can also bring destruction. Human waste — such as sewer leaks, runoffs, and pesticides — can flow into caves disrupting an ecosystem so sensitive it is said that even human dandruff can upset its balance.

Excavations and the building of roads can also threaten cave life directly. It’s important to note that most of the world’s caves have yet to be fully explored or discovered. The limestone labyrinths beneath us are indeed the earth’s last frontier. It’s a fascinating notion –- some of us may be living above an ecosystem populated by strange species, some millions of years old, and not even know it. In 2007, environmental protection officials in Australia halted a multi-billion dollar iron ore mining proposal when 11 species of troglobite were discovered in the area to be mined. Unfortunately, the ruling was overruled several months later. The battle between moneyed interests and our wildlife continues, unfortunately with greater frequency and scope.

Troglobites are at great risk. This includes the beloved olm which is presently listed by the IUCN as threatened, a circumstance that should be taken very seriously, not only because we should be stewards of our planet (above its surface and below) or because the olm is a fascinating, wonderful species, but also because it is the olm’s very sensitivity to such things as pollution that portends what affects humans as well.

Photo © WNET.ORG/Icon Films

“It’s the most awesome thing I’ve ever seen.” That is how K. Michael Garman, a cave diver and researcher featured on NATURE’s Springs Eternal, describes the Dragon’s Lair, an unusual cavern he is studying in Crystal Beach Spring on Florida’s west coast.

As Springs Eternal shows, the Dragon’s Lair gets its name from a remarkable layer of bacteria that grows suspended in the water, lying like a smoky cloud between a heavier layer of salty water and a lighter layer of fresh water. “Some days it is thin and wispy, other days it’s thick and looks like solid bottom,” says Garman, who has probed the Lair’s depths dozens of times along with his wife Sherry and other divers. But the cloud never ceases to enthrall him, he says. “Every time I turn the corner [into the Lair], I’m afraid it will be gone,” he says.

Exploring in the dark can be perilous.

Getting into the cavern network is no easy task, as Springs Eternal illustrates. Unlike most Florida springs, which exit on land, Crystal Beach Spring emerges from the seafloor of the Gulf of Mexico. To enter, divers must go offshore and swim down to the entrance, a narrow, rubble-filled hole barely big enough to squeeze through. But by shedding their equipment and dragging it through the opening, the divers are able to enter a mystical — and dark — world.

Garman, however, says the lack of light makes things more interesting. “I’ve never been bored in a cave,” he says. “When you are diving on a reef, you are often looking at just another fish. But in a cave you notice a lot more detail because you are focused narrowly on what your light is showing you.”

In Crystal Beach Spring, he’s found plenty to look at. There are blind crayfish, small crustaceans, and snails. And each room in the maze-like cavern has its own feel. Besides the Dragon’s Lair, for instance, there is Thunder Road, the cave’s main passage, and the Bacteria Room, which earned its name from the orange bacterial and fungal mats that line its nooks and crannies. Eventually, Garman, a graduate student at the University of South Florida, hopes to write a thesis on the cavern’s unusual food web, which is based on the bacteria’s ability to live on sulfur extracted from the sea water.

Such research is not for everyone. Cave diving is a dangerous activity that requires extensive training, Garman notes. New technologies — from brighter lights to more dependable breathing gear — have made the sport safer and easier, he says, but are no substitute for experience and good judgement. “We’ve had things go wrong, such as a light going out, where we’ve called a dive and exited the cave,” he says. “Sometimes, you just have to say: ‘The cave’s going to be here next week, and we can come back.’ It’s just the smart thing to do.”