In a fascinating and somewhat eerie development, a unique form of transmissible cancer has been discovered among catfish in Lake Memphremagog, a body of water shared by Vermont and Quebec. This mysterious cancer, characterized by dark streaks on the fish's skin, has scientists intrigued and searching for answers.
The story begins with an annual fish census conducted by the Vermont Fish & Wildlife Department. In 2013, researchers noticed something unusual about the brown bullhead catfish in the lake. A quarter of these catfish displayed unsettling dark streaks, a phenomenon that had not been observed before.
"It's like black tar on the skin, not a pretty sight," says Peter Emerson, a fish biologist involved in the census. "You can tell it's not helping the fish; they're inside the mouth, on the fins, sometimes even covering their eyes."
A paper published in Nature reveals that these dark blemishes are, in fact, a type of transmissible skin cancer, spreading from catfish to catfish. This discovery is significant as transmissible cancer has only been identified in a few other animals, including Tasmanian devils, dogs, and certain molluscs.
Julie Dragon, a data scientist and co-author of the study, explains, "It's the infectious agent itself. Those cells can escape the host, maybe live in the aquatic environment, and then infect a new host."
The initial assumption was that the melanoma was caused by exposure to UV rays or a chemical pollutant, given the proximity of the Coventry Landfill. However, tests revealed that the catfish had minimal exposure to toxins.
"As we did the studies, it turned out they didn't have much of that at all," Emerson notes.
Genome sequencing then revealed something even more intriguing. Typically, tumors resemble their host genetically, but these catfish tumors were remarkably different from their hosts, suggesting they were clones that had spread between fish.
Vincent Lynch, an evolutionary biologist not involved in the research, describes it as a cancer with "a life of its own." He suggests these catfish could be valuable in studying how cancers metastasize and migrate within our bodies, potentially leading to insights that could stop cancer deaths.
The researchers will continue to study catfish melanomas in other lakes and ponds, including a possible early documentation by Henry David Thoreau. The authors also argue that transmissible cancers might be more common than previously thought.
Personally, I find this story incredibly fascinating. It raises questions about the evolution of cancer and its ability to adapt and survive, almost like a living entity. It's a reminder of the complex and often mysterious ways in which life forms interact and adapt to their environments. This discovery could open up new avenues of research and potentially lead to breakthroughs in cancer treatment. It's a story that highlights the importance of scientific curiosity and the unexpected discoveries that can emerge from it.
