A genome study has proven that all specimen of Marmorkrebs, or marbled crayfish, originate from a single female. About 30 years ago, the original clone evolved in an aquarium. Ever since, the female animals have been able to spread successfully without any help from males, scientists from the German Cancer Research Center (DKFZ) report in a current publication. The clonal genome evolution of the crayfish may also help explain processes in tumors.