A new study suggests cancer that's killing clams on the East Coast has a unique characteristic—it's contagious. Assuming the research is correct, it would be only the third example of this in nature, the first two involving dogs and Tasmanian devils. But the findings suggest that this kind of thing "is more widespread in nature than previously supposed," the scientists write in the journal Cell. Researchers at Columbia University made the discovery while studying leukemia that has been plaguing the clams for decades. To their surprise, they found that cancer cells in different clams had nearly identical DNA, and the DNA didn't match the genes of the host clams. As National Geographic explains, the tumors "hadn’t arisen in their hosts; they had arrived there."
How? The best guess is that the cancer originated in some long-ago clam, and its cancer cells were then spread through seawater. NPR further explains that clams filter huge amounts of water through their bodies, and "they might simply siphon up these free-floating cancer cells and literally catch cancer." The research is intriguing but not definitive, says a marine biologist at the University of New Hampshire, adding that "it's very clear that something unusual is going on here." Researchers will next try to confirm and to see if something similar is happening in other species. Columbia's Stephen Goff tells the Washington Post that the research could shed light on how cancer spreads in humans. "I think this could teach us about metastasis," he says. "It has the potential to teach us a lot about how cells can colonize in a new site." (Click to read about a dog who can sniff out cancer.)