By Pauline Davies
Michael Metzger and his colleagues have observed the widespread transmission of cancer within a species of bivalve or soft-shell clam. The cancer is spread in sea water and can wipe out whole populations. One cancer detected in a Pacific species was later found in the Atlantic. It raises questions about the prevalence of transmissible cancers in the natural world. The transmissible cancers are not only found in marine species. Other notable examples are the facial tumour disease of the Tasmanian Devil and cancer of dogs.