Scientists have found the strongest evidence to date that cancer is extremely rare in turtles – which could help prevent and even fight the disease in humans.
The new analysis, published in BioScience, shows that only around 1% of individuals are affected – far less than in mammals or birds.
As part of the study (which was led by Dr Ylenia Chiari from the University of Nottingham alongside Dr Scott Glaberman from the University of Birmingham), the team worked in collaboration with researchers from zoos across the UK, US and Europe to analyse medical records and necropsies (autopsies) from hundreds of zoo turtles.
Not only did the findings show that there low numbers of cancer cases among turtles, but when tumours did appear, they almost never spread.
So why are turtles resistant to developing cancer?
The researchers attributed turtles’ resistance to cancer to their strong defences against cell damage, slow metabolism that reduces cellular stress and unique genes that protect against cancer. Turtles could therefore offer insightful clues for preventing or treating cancer in humans.
Dr Ylenia Chiari said: “Turtles, especially iconic species like Galápagos and Aldabra giant tortoises, are famous for living long lives and growing to tremendous sizes. You’d expect that to mean more cancer, but our study, which combines decades of zoo records with previous research, shows how incredibly rare cancer is in these animals. It highlights turtles as an untapped model for understanding cancer resistance and healthy aging.”
Peto’s paradox
This research comes after a study from the University of Reading, which disputed the decades-long puzzle of Peto’s paradox.
A famous study in 1977, later named Peto’s paradox, suggested that there was no link between an animal’s size and its chances of developing cancer – despite previously accepted ideas that the bigger an animal was, the greater its chances of developing cancer, since more cells meant more opportunities for mutation.
But studies have slowly been challenging this longstanding hypothesis, including the aforementioned one from the University of Reading. It found that larger animals consistently showed a higher prevalence of benign and malignant tumours, and that species which evolved to be larger more rapidly (such as elephants) developed better natural defences against cancer.
Although the study didn't include Testudines reptiles (the genus to which turtles belong), the low cancer rates demonstrated in species such as Galapagos and Aldabra giant tortoises, which can grow to large sizes and live beyond 150 years, are further evidence to the contrary of Peto’s paradox.
Read the full study: Do turtles get cancer?
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Main image credit: Getty