For centuries, people have been looking for ways to prolong life. From explorers seeking the legendary Fountain of Youth to the latest diet craze, the search has continued. More recently, scientists began looking at a region at the end of chromosomes, called the telomere, which shortens as animals age. These regions protect the DNA from mutation and degradation, and help to stabilize the chromosome. Unlike humans and other mammals, lizards can prevent their telomeres from shortening. However, while the reptiles are developing in their eggs, the mechanisms by which they prevent this may be overwhelmed – especially if the temperature outside gets too hot for them. Armed with this knowledge, Alexander Hansson and Mats Olsson of the University of Gothenburg, Sweden, with Erik Wapstra and Geoffrey While from the University of Tasmania, Australia, set out to discover what happens to the telomeres of sand lizards (Lacerta agilis) when they develop in warmer temperatures.
Between 2018 and 2020, Hansson and colleagues captured pregnant female lizards on St Keholmen, a small island off the west coast of Sweden, and brought them back to the lab. They then began the difficult task of collecting the eggs laid and raising them at cool (23°C), warm (25°C) or hot (27°C) temperatures. When the baby lizards hatched, they were placed in enclosures that fluctuated between 15°C and 20°C, and the team measured the length of their telomeres by collecting DNA from the reptile's tissues. The temperature that the eggs were raised at didn't seem to affect the telomeres of the newly hatched lizards. But when the scientists compared the lengths of the telomeres between the male and female lizards, they found something remarkable. ‘We did predict that there would be some variation in telomere length between males and females, but we were surprised by the drastic difference already present at hatching, where females had telomeres that were 34% longer than the male's telomeres,’ says Hansson. The researchers suggest that the longer telomeres show that females are investing in their longevity more than males, probably to allow the female lizards to have more offspring over their lifetime.
Following their unexpected finding that eggs incubated at warmer temperatures did not produce lizards with shorter telomeres, the team measured the length of the lizard's telomeres a second time, but after waiting for the lizards to grow a bit older. After just a few weeks, the telomeres of lizards incubated at the hottest temperature had shrunk even though they hadn't experienced the higher temperatures recently. If the lizards can't lengthen their telomeres again, there could be long-term consequences for sand lizards in the future such as a shorter lifespan and having fewer babies. But could these shorter telomeres affect the next generation as well?
Hansson and colleagues measured the length of the telomeres in the mothers they caught in the wild and found that mothers which had longer telomeres had babies whose telomeres were less likely to shorten over time. However, if the temperatures continue to rise and their eggs are subjected to warmer weather, the mothers will continue to pass on shorter and shorter telomeres to their children. This, then, could also lead to lizards that have fewer babies and shorter lives. Climate change is making the world warmer, and, at least for reptiles, could also be taking away the anti-aging secret that humans have been seeking for so long.