India, July 28 -- A newly discovered catfish skin cancer joins Tasmanian devils, dogs and shellfish as one of the few species with naturally transmissible tumours.

In these animals, cancer cells themselves spread between individuals and survive as independent lineages.

In humans, strong immune rejection, high genetic variation and cell vulnerability prevent such cancers, though studying them reveals how tumours evolve and evade defenses.

Scientists in Vermont have just discovered something that shouldn't really be possible: a skin cancer that's spreading from catfish to catfish. It's only the fourth transmissible cancer ever found in nature.

Catfish now join Tasmanian devils, dogs and shellfish as the only animals known to carry natur...