A new study suggests direct transmission of cancer among some marine animals may be more common than once thought, as research revealed that contagious cancer cells among several species of bivalves, including mussels and clams, spread from animal to animal through sea water.

The study, published in Nature, was conducted by researchers at Columbia University Medical Center (CUMC), and involved the contagious cancer known as disseminated neoplasia, a leukemia-like illness that affects many bivalves, according to a news release.

Dr. Stephen Goff, a Higgins Professor of Biochemistry in the department of biochemistry and molecular biophysics and the department of microbiology and immunology at CUMC, was among a team of researchers who previously observed direct transmission of cancer cells in soft shell clams. They then explored if cancers in other mollusks are also caused by contagious cells.

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Researchers examined the DNA of cancers and normal tissue from mussels, cockles and golden carpet shell clams found in waters off the coast of Canada and Spain, according to the news release. The analysis revealed that the cancers were caused by independent clones of cancer cells that were genetically distinct from their hosts. In the carpet shell clam, the infectious cancer cells came from a related by distinct species, a result of cross-species transmission.

“Now that we have observed the spread of cancer among several marine species, our future research will investigate the mutations that are responsible for these cancer cell transmissions,” Goff said in the news release.