Scientists have sequenced the genome of the blind mole rat, a mammal that digs with its teeth, has skin over its eyes and lives for more than 20 years. It is also resistant to cancer, like its distant cousin the naked mole rat.
Among the results were what the researchers believe are the genetic signatures of the mole rat's complete loss of vision and its impressive tolerance of low oxygen (or "hypoxia"). They also discovered how its special cancer-fighting mechanism might have evolved.
One of the study's lead authors, Prof Eviatar Nevo from the University of Haifa in Israel, has studied blind mole rats for more than 50 years. In all of that time, a spontaneous tumour has never been discovered.
Even when treated with carcinogenic chemicals, these remarkable rodents were incredibly resistant to cancer.
Most animals rely on cells detecting a cancerous malfunction and shutting themselves down (programmed cell death or "apoptosis"), but the blind mole rat's immune system attacks tumours and causes "necrosis" instead. The new study reports that genes involved in this immune defence have been favoured by evolution, and some have been expanded or duplicated.
All this may have happened because one of the key mediators of the normal cell-shutdown defence, a protein called p53, is mutated in the mole rats as part of their adaptation to low oxygen.
The mole rat spends its entire life under the ground, where oxygen is scarce. In other animals this would send p53 into overdrive. "When there is low oxygen, in other species, normal p53 would mean that some cells would die from apoptosis - but not in blind mole rats, because that would be a disaster," said Dr Denis Larkin from the Royal Veterinary College in London, one of the study's authors.
So the mole rats have evolved a unique trade-off, weakening p53 and boosting the immune system's necrotic defence, which "the cancer doesn't know how to deal with," Dr Larkin.
The blind mole rat (the newly sequenced species is Spalax galili) is only distantly related to the naked mole rat (Heterocephalus glaber), another unusual, subterranean critter with remarkable cancer resistance.
Their evolutionary histories diverged over 70 million years ago, according to calculations in the new study, and the two mole rats adapted completely separately to life underground.
The new work, published in the journal Nature Communications, will help unpick those secrets and the wider adaptation of animals to difficult environments.