The genetic sequence of the late giant tortoise, Lonesome George, has shed light on the extraordinary characteristics of his species.
Using their findings, researchers from around the world have put together a list of genes to examine, to figure out their connection to cancer and longevity.
In a collaborative project involving Yale University, University of Oviedo, Galapagos National Park Service, Flinders University and another nine institutions, scientists analysed the genomes of Lonesome George, the last member of Chelonoidis abingdonii, and the Aldabra giant tortoise (Aldabrachelys gigantea), comparing them to other species, including humans.
“The reason why we picked the giant tortoise is because they are some of the longest-lived animals, and therefore they have probably evolved some genetic mechanisms for reducing their risk of developing cancer,” said co-author and Professor of Biodiversity Genetics at Flinders University Luciano Beheregaray.
The researchers identified several variants in the tortoise genomes that potentially affect six of the nine hallmarks of ageing.
They also found some genes which could be important for cancer in humans were found duplicated in the giant tortoise.
Giant tortoises and humans share more than 90 per cent of their DNA, but Professor Beheregaray said it was the differences that made the comparison interesting.
“Several of those genes are found as a single-copy gene in humans, but in giant tortoises, some of those have duplicated, so you have two copies of the genes, and some of those have three copies,” he said.
“And we know that gene duplication impacts on the function of the genes.”
The hope is that researchers are able to replicate these genes in the lab.
“So, it might be – and that is work that is needed in the future – that those duplications are indeed impacting on the ability of giant tortoises to live very long lives,” Professor Beheregaray said.
Giant tortoises are not cancer-free, but along with several reptiles, they have very low rates of the disease.
“At the end of the day, cancer relates to problems during cell division,” Professor Beheregaray said.
When the cell divides, the DNA eventually make errors in the division.
“Therefore [giant tortoises] could have evolved mechanisms to prevent that.
“And we have now a very good list of potential genes that people can investigate further to try to establish those associations.”
While it is hoped the research will increase understanding about ageing and cancer in humans, the work is also of benefit in the conservation of giant tortoises.
The International Union for Conservation of Nature (IUCN) lists six species of giant tortoise as critically endangered, three as endangered, three as vulnerable, and one, possibly two, more as extinct.
It is hoped the knowledge gained about the species’ characteristics and evolution will aid efforts to rebuild populations where it is still possible.