There there is no darkness like being in a cave. I like to turn off my headlamp to experience it. It probably sounds horrifying and disturbing, but caves also have a peaceful quality to them – at least to me. It’s like the earth giving me a hug. I’m strangely calm when I’m in a cave.
As a professor and curator of fish at Louisiana State University, I explore hidden corners of the world and find new species, which means going places few people have been before.
Caves are sometimes home to 20 foot crocodiles, or freshwater eels the thickness of my arm, which can be really aggressive and look like pythons on land. I saw tarantulas the size of my hand jump across the surface.
My focus is cavefish, which evolved to be blind and pale. They look like little ghosts, with their white, flowing fins moving slowly, sometimes towards you because they are not used to predators. They’re often only three inches long, so it’s not that scary. But it is a privilege to see wildlife come to you – it rarely happens.
I am a systematist, which is someone who studies the tree of life and finds out who is related to whom, often with DNA. Sometimes we add new branches to the tree by discovering species new to science. I have described 15 species of fish, several of them cave fish. My favorite is Typhleotris marybe of Madagascar, which means “great disease” in Malagasy. It was my first time going into a cave and it must have put me off my game forever.
That was in 2008, and the sinkhole was called Grotte de Vitane, which is part of a partially uncharted system of waterways in the southwest of the country. The sinkhole is sacred to local people, but apparently they didn’t know about this little fish living inside. They didn’t swim in it either – for good reason, it seems.
At the time I knew very little about caves and was not a good swimmer. I swam around for about half an hour and saw nothing. But my colleague John Sparks from the American Museum of Natural History continued snorkeling for another two hours or so. Finally, he passed on a copy for me to look at – I knew it was new the moment I saw it.
Cavefish are generally white, or depigmented pinkish, with no eyes, but this one was very dark. No one had described or talked about a darkly pigmented cavefish before. I was instantly in love. I thought, “Holy crap, this is really cool. It’s the most amazing thing I’ve ever seen.” It was beautiful – or maybe just I find it beautiful.
I just didn’t expect it – a cave fish with an adaptation to being in the light. Part of this cave system receives light and it is probably beneficial to be dark so that birds and other possible predators cannot see it near the surface. And it works because it was really, really hard to find.
It was three or four inches long, and very thin. We later found that the closest relative of these southern Malagasy cavefish lives over 6,000 km (3,700 miles) away in Australia. How could such a small fish find its way across the Indian ocean? I don’t think it did – it’s more likely that the continents moved and separated more than 100m years ago. As far as we know, these species only live in underground systems in Madagascar and Australia.
Not only did we discover a new fish on this trip, we also discovered a new disease.
Back then we weren’t worried about disease, I was more worried about crocodiles. Then in the days and weeks after this first field site, people developed a viral disease that no one could identify. We called it “sinkhole fever.” Some people got so sick that they had to go home early. It was John’s idea to call this new species “big disease”.
There are about 200 species of cave fish, and this is a very small percentage of the 35,000 species of fish. I think we’ve added about 100 in the last 20 or so years because we’re exploring some very remote caves in places like China. I wouldn’t be surprised if twice as many cave fish are discovered in the next 10 years.
We don’t know how long many of these cavefish species live, or how they reproduce. There are some cave salamanders that don’t eat for years. It is a mystery how many of these species entered these caves, why and when. Some are washed into caves and then find ways to survive and diversify over millions of years. Others arrived more recently and quickly adapted to underground life.
People often think we know every nook and cranny on earth, but the more we look, the more we find – amazing things are out there. Sometimes we become cynical about the loss of organisms and extinction occurring at an incredible rate, but discoveries are also occurring at an incredible rate. We need more people to go out there and look for things, work with the people who live in these areas and learn from them.
There is still a lot of space for people who are driven and curious and want to find new life in scary, dark caves, because there is so much beauty to be found in them.
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As told to Phoebe Weston. Prosanta Chakrabarty is professor of cyctiology, evolution and systematics at Louisiana State University. He studies the evolution and biogeography of freshwater and marine fish
