In the freshwater borderlands between Vermont and Quebec, a discovery has quietly rewritten what science thought it knew about cancer's reach: brown bullhead catfish in Lake Memphremagog are passing malignant melanoma between one another, not through genes inherited at birth, but through living tumor cells that leap from body to body like a parasite wearing cancer's face. This is only the fourth transmissible cancer ever documented in nature, and the first found in any fish, suggesting that one of biology's strangest phenomena may be far older and more widespread than the handful of known case
Scientists discover first transmissible cancer in fish species
Lake Memphremagog supplies drinking water for over 175,000 people; long-term ecological impacts on fish populations remain unclear.