In other words, the cancer that has killed so many clams all trace to one incidence of disease. The cancer originated in some unfortunate clam somewhere and has persisted ever since as those cancerous cells divide, break free, and make their way to other clams.
Stephen Goff, of the Howard Hughes Medical Institute and Columbia University, said: "The evidence indicates that the tumour cells themselves are contagious - that the cells can spread from one animal to another in the ocean.
"We know this must be true because the genotypes of the tumor cells do not match those of the host animals that acquire the disease, but instead all derive from a single lineage of tumor cells."
There was bad news for Chile's national fisheries this week after a study of the health of its fish stocks found eight are in a state of collapse and some others of being over-exploited.
The report 'Current Status of Major Chilean Fisheries' reported that eight fisheries are depleted, eight in a state of over-exploitation and 22 in a state of full exploitation.
The important hake fishery between the regions of Coquimbo and Los Lagos was found to be in a delicate condition, being classified as in a state of exhaustion or collapse.
A new project from Australia's Queensland Department of Agriculture and Fisheries has found that culturing prawns and worms in the same integrated system can lead to improved productivity and waste management.
The two-year study is testing the concept of fully recirculating pond water from intensive prawn culture ponds through polychaete-assisted sand filters (PASF), to create sustainable supplies of prawns and marine worms.