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I found a type of fish in a cave that we called ‘big sickness’ – with good justification.


There is no feeling quite like being in a cave without any light. I enjoy shutting off my headlamp to fully embrace it. It may seem scary or unsettling, but caves also have a calming and tranquil atmosphere – at least for me. It feels like the Earth is embracing me. I feel surprisingly relaxed in a cave.

In my role as a professor and fish curator at Louisiana State University, I venture into uncharted areas of the world in search of previously undiscovered species. This often involves visiting remote locations that have been rarely explored by others.

Large crocodiles, as long as 20 feet, and thick freshwater eels can often inhabit caves. These creatures can display aggressive behavior and can resemble pythons when on land. I have also witnessed tarantulas as big as my hand crawling on the surface.

I am interested in studying cavefish, a species that has adapted to living in darkness and have a pale appearance. They have a ghost-like appearance with their white fins gracefully gliding through the water, often moving slowly towards you because they are not used to predators. Despite their eerie appearance, they are typically only three inches in length, so there is no need to be afraid. It is a rare and special experience to have wildlife approach you.

The Ozark cavefish

I am a scientist who specializes in systematically studying the relationships between various organisms, often using DNA. Occasionally, we expand the tree of life by identifying new species that have not been previously documented. I have identified and classified 15 types of fish, including several that live in caves. My preferred species is Typhleotris mararybe, found in Madagascar, which translates to “big sickness” in the Malagasy language. This discovery was my first experience exploring a cave and it should have deterred me from caving forever.

In 2008, a sinkhole named Grotte de Vitane was discovered in the south-west region of the country. It was part of a complex network of waterways that had not been fully mapped. Although the sinkhole was considered sacred by the local community, they were unaware of the existence of a small fish living inside. Due to this and other reasons, they did not swim in it.

During that period, I had limited knowledge about caves and my swimming skills were not strong. I spent approximately thirty minutes swimming around but did not spot anything. Meanwhile, my colleague John Sparks from the American Museum of Natural History kept snorkeling for another two hours. Eventually, he handed me a specimen to examine – I could tell it was a new discovery as soon as I laid eyes on it.

Typhleotris mararybe, a cave-dwelling fish from Madagascar

The typical appearance of cavefish is pale or pinkish due to a lack of pigmentation and absence of eyes, but this particular one was unusually dark. No previous observations or discussions had mentioned a darkly colored cavefish. I was immediately fascinated by it. My initial thought was, “Wow, this is incredibly interesting. I’ve never seen anything like it.” To me, it was stunning, although others may not share my opinion.

I was surprised to discover a cavefish with a physical characteristic that allows it to thrive in light. This particular cave has some areas that are illuminated, so it is advantageous for the fish to have a dark color to avoid being spotted by birds or other potential predators near the surface. This adaptation proved successful, as it was challenging to locate the fish.

The fish was approximately three to four inches in length and had a slim appearance. After further investigation, we discovered that the most similar species to these cavefish in southern Madagascar reside over 6,000km (3,700 miles) away in Australia. One may wonder how such a small fish could make its way across the vast Indian Ocean. However, it is unlikely that the fish traveled itself, as it is more probable that the continents shifted, separating the two locations over 100 million years ago. Currently, these particular species are only found in underground systems in Madagascar and Australia.

During this journey, we not only came across a previously unknown fish, but we also encountered a new illness.

Prosanta Chakrabarty, who specialises in cavefish, in a cave with the light entering from high above him.

During that period, our concern was not focused on illnesses, but on the threat of crocodiles. However, in the following days and weeks at our initial research location, individuals began experiencing an unidentified viral sickness. We gave it the name “sinkhole fever”. The severity of the illness caused some individuals to leave the field site early. John suggested naming this newly discovered species “big sickness”.

There are approximately 200 types of cavefish, which is a relatively small number compared to the total 35,000 fish species. It is estimated that around 100 new species have been identified in the past 20 years, as we continue to explore remote caves in countries like China. It is possible that twice as many cavefish will be discovered in the next decade.

The lifespan and reproductive habits of numerous cavefish species are unknown. Certain cave salamanders have been observed to go without eating for extended periods of time. The reasons and timing behind the entrance of these species into caves remain a mystery. Some were likely carried into caves by strong currents and evolved to thrive over millions of years, while others arrived more recently and swiftly adapted to life underground.

Many believe that we have thorough knowledge of all corners of the world, but the deeper we delve, the more astonishing discoveries we make. While we may become pessimistic about the decline of species and the alarming rate of extinction, we must also recognize that amazing findings are being made at an equally astounding pace. It is crucial to involve more individuals in exploring and collaborating with local communities to learn from their insights.

There is ample opportunity for individuals who are motivated and inquisitive to discover new wonders in the frightening depths of caves, as they hold immense beauty within.

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    Phoebe Weston recently interviewed Prosanta Chakrabarty, a professor at Louisiana State University who specializes in the study of the evolution and biogeography of freshwater and marine fishes.

Source: theguardian.com