If you were to go to Constanta county, a small, barren plain that lies in south-eastern Romania, you would find a completely desolate area over a cave named Movile Cave that holds some pretty bizarre creatures. This cave and the creatures it holds have been isolated from the rest of the world for 5.5 million years. As everything in the world changed, these creatures stayed the same, according to BBC News.
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Even though there is no light and the air is teeming with poison, there is an abundance of life within the cave. There are spiders, scorpions, centipedes, and wood lice - many of which we probably don't even know about. They survive due to a strange floating mat of bacteria.
The cave was found in 1986 when workers in communist Romania were testing locations to see if they were suitable for a power plant. Romanian scientist Cristian Lascu was the first to go into the cave, a 20m journey by rope into the ground.
Since Lascu was in the cave, it was sealed and fewer than 100 people have been allowed inside, partly because the journey into the cave is so dangerous.
In order to enter the cave, you have to lower yourself by rope using only the light from your helmet. You then enter a humid, dark world where you have climb down through limestone tunnels. Eventually, you will find a lake that is surrounded by harmful gases.
A microbiologist, Rich Borden, was the 29th person to visit the cave in 2010.
"It's pretty warm, and very humid so it feels warmer than it is, and of course with a boiler suit and helmet on that doesn't help," says Boden, who works at the University of Plymouth in the UK.
"The pool of warm, sulphidic water stinks of rotting eggs or burnt rubber when you disturb it as hydrogen sulphide is given off."
Anyone who has been in there says that it is terrifying. The air has half of the normal oxygen, resulting in headaches and other problems. Visitors are only able to stay for around 6 hours before their kidneys pack in.
Exploring the rest of the cave requires you to swim in the lake and navigate underwater passageways, some of which require you to slip through tiny gaps in the rock to emerge into air-filled spaces.
As you can imagine, it is very easy to get lost.
Still it is very important for us to get in there, because of the 48 species identified, 33 are found nowhere else in the world. There are questions about how they get their food. Some of them have taken to eating things they normally would because it is all that is there.
The worse the air gets, the more animals you will find.
On the surface, plants will use sunlight to extract carbon dioxide from the air and turn it into an organic compound. From there, they use these chemicals to grow. Animals then feed on the growth.
Many caves don't have sunlight, so animals get their food from water that drips from the surface - the same water that forms stalactites and stalagmites. This doesn't happen in Movile Cave as any and all water comes from a deep underground reservoir.
Even weirder is that the water isn't coming from above into the reservoir either, and has to be coming from below. It appears that the water is coming from spongy sandstones where it has been for 25,000 years.
But how do these animals survive?
There is a frothy foam sitting on top of the water that holds the secret. It contains millions of bacteria called "autotrophs."
"These bacteria get their carbon from carbon dioxide just like plants do," says Boden. "The carbon dioxide level in the cave is about 100 times higher than normal air. But unlike plants, they obviously can't use photosynthesis as there is no light."
Instead of using light to get energy, they use a process called chemosynthesis, which explains why there is so much carbon dioxide in the air.
"They get the energy needed… from chemical reactions: the key ones being the oxidation of sulphide and similar sulphur ions into sulphuric acid, or the oxidation of ammonium found in the groundwaters to nitrate," says Boden.
Movile is likely the only cave that survives this way.
"Sulphuric acid actually erodes the limestone, which is gradually making the cave bigger," says Boden. "The process releases carbon dioxide, which is why levels are so high."
Another group of bacteria, methanotophs, uses the methane gas and carbon that bubbles up through the water.
Boden said that methanotrophs are "messy eaters" that "constantly leak metabolic intermediates like methanol and formate" into the surrounding water.
According to microbiologist J. Colin Murrell of the University of East Anglia in Norwich, UK, the bacteria in Movile Cave are remarkably simple and not at all unusual.
"The bacteria get all of their carbon from just one source, be it methane or carbon dioxide," says Murrell. "That means that all of the components of their cells, be it the DNA in their nucleus, the lipids in their cell membrane and the proteins in their enzymes, are made from the same simple ingredient."
These bacteria are also similar to bacteria that you can find elsewhere, even though they have been trapped for millions of years.
"Methanotrophs are everywhere: the Roman Baths at Bath, the surface of seawater, the mouths of cattle and probably the human mouth and gut," says Boden. "Autotrophic bacteria of the same types we found at Movile are found in almost all soils and on the surface of the skin."
The animals are a different story. Some don't have eyes, others have lost all pigment. Extra long antennae have sprouted for many of them.
No one really knows how these animals ended up in the cave either. One theory is that the animals had to seek refuge when the climate of the northern hemisphere changed.
The problem with this theory is that it is difficult to prove.
"It's very likely that the bacteria have been there a lot longer than five million years, but that the insects became trapped there around that time," says Murrell. "They could have simply fallen in and become trapped when the limestone cast dropped, sealing the cave until it was discovered again in 1986."
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However they got there, it seems that Movile's inhabitants are now trapped for good, which is a shame because we could learn a lot from them - including more about the very first creatures on earth.