There is no darkness like being in a cave. I love turning off my headlamp to experience that. It probably sounds horrifying and disconcerting, but caves also have a peaceful quality to them – at least for me. It’s like Earth giving me a little hug. I’m weirdly calm when I’m in a cave.
As a professor and curator of fishes at Louisiana State University, I explore hidden corners of the world and find new species, which means going to places few people have been before.
Caves are sometimes home to 20ft crocodiles, or freshwater eels the thickness of my arm, which can be really aggressive and look like pythons on land. I’ve seen tarantulas the size of my hand skipping across the surface.
My focus is cavefish, which have evolved to be blind and pale. They look like little ghosts, with their white, flowing fins, moving slowly, sometimes towards you because they’re not used to predators. They’re often only three inches long so it’s not that scary. But it’s a privilege seeing wildlife coming towards you – that rarely happens.
I’m a systematist, which is someone who studies the tree of life, figuring out who is related to who, often with DNA. Sometimes, we add new branches to the tree by discovering species new to science. I’ve described 15 species of fish, several of them cavefish. My favourite is Typhleotris mararybe from Madagascar, which means “big sickness” in Malagasy. It was the first time I’d gone into a cave and it should have put me off caving for ever.
It was in 2008, and the sinkhole was called Grotte de Vitane, which is part of a partially unmapped system of waterways in the south-west of the country. The sinkhole is sacred to local people but they apparently didn’t know about this little fish living inside. They also didn’t swim in it – for good reason, it turns out.
At the time I knew very little about caves and was not a great swimmer. I swam around for about half an hour and didn’t see anything. But my colleague John Sparks from the American Museum of Natural History continued snorkelling for another two hours or so. Finally, he passed up a specimen for me to look at – I knew it was new as soon as 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 absolutely enamoured right away. I thought, “Holy crap, this is really cool. This is the most amazing thing I’ve ever seen.” It was beautiful – or maybe only I find it beautiful.
I just didn’t expect it – a cavefish with an adaptation for being in the light. Part of this cave system receives light and it’s probably beneficial to be dark so birds and other possible predators can’t see it near the surface. And it works, because it was really very 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 live more than 6,000km (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, separating them more than 100m years ago. As far as we know, these species only live in subterranean systems in Madagascar and Australia.
Not only did we discover a new fish on this trip, we also discovered a new sickness.
At the time, 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 sickness that no one could identify. We called it “sinkhole fever”. Some people got so sick they had to go home early. It was John’s idea to call this new species “big sickness”.
There are about 200 species of cavefish, and that’s 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 really remote caves in places such as China. I wouldn’t be surprised if twice as many cavefish 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’s a mystery how many of these species entered these caves, why and when. Some get flushed into caves and then find ways to survive and diversify over millions of years. Others arrived more recently and quickly adapted to subterranean life.
People often think we know every nook and cranny on the Earth, but the more we look, the more we find – wonderful things are out there. Sometimes, we become cynical about loss of organisms, and extinction happening at an unbelievable rate, but discoveries are happening at unbelievable rates, too. We need more people to go out there and look for stuff, working with the people who live in these areas and learning from them.
There is still lots 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 ichthyology, evolution and systematics at Louisiana State University. He studies the evolution and biogeography of freshwater and marine fishes
