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wood lizard
Photo: Karin Jähne / Shotshop / IMAGO
Temperatures are rising due to the climate crisis - and now lizards in France are giving birth to offspring in which heat stress has altered the DNA: their telomeres, protective caps at the ends of chromosomes, also known as the "fuses of death" because they are related to the aging process have are significantly shortened.
The lizards are old, even if they are newborn.
This is indicated by a study published in the »Proceedings of the National Academy of Sciences« by experts led by the biologist Andréaz Dupoué from the Ifremer research institute in France.
They studied ten different colonies of wood lizards in the French Massif Central.
The wood lizard is considered one of the most widespread lizard species in the world, found throughout Eurasia, from Spain to Japan.
blood samples and tail pieces
For more than a decade, experts have been taking blood samples from the lizards' eyes and pinching off tiny pieces of their tails to catalog the genetic material of hundreds of the animals.
Since the reptiles like to be in the grasslands, they are not that difficult to capture.
In the laboratory, they analyzed the telomeres as a parameter for aging processes in the body.
Science assumes the following process: the more often a cell divides, the shorter the telomere becomes.
If the telomere becomes too short at some point, the cell can no longer divide and dies.
Stress can also lead to shortened telomeres, this is already known and has also been observed in humans: trauma caused by bullying, sexual or domestic violence shorten the telomeres in children.
In the present case, the lizards are also under stress: from the heat.
Danger for turtles and crocodiles?
The team found that in declining and heat-affected populations, telomeres are unusually short.
Since females are likely to pass on their shortened telomeres to their offspring, this could shape the animals for generations and possibly lead to their extinction.
With rising temperatures, this could become even more of a problem.
France has been struggling with particularly hot summers for years, this year the rails near Bordeaux reached 53 degrees, in May France experienced a historic heat wave, and July was also hotter than almost ever.
As early as 2019, it was warned that the risk of heat waves had increased fivefold.
Of the ten lizard populations studied, one was completely extinct by the end of the study period.
Nevertheless, the forest lizard is not in existential danger.
It is considered hard-boiled and adapts particularly well to cold, in winter it can freeze and survive.
But if the study results are transferrable to other reptile species, they could face bigger problems.
More than a fifth of all reptiles are already threatened with extinction, including turtles and crocodiles.
Telomeres: cause or indicator?
At the same time, examining telomeres could also be an opportunity: an indicator of how much stress a population or animal species is under - or how much conservation measures reduce the stress on the animals.
Telomeres have not yet been fully investigated in humans either.
It has been proven that they are related to the aging process and that a high number of short telomeres is considered unfavorable.
However, aging is a process influenced by several factors, of which the length of telomeres is only one.
People with shortened telomeres live an average of 3.6 years shorter, according to a study in 2010. So telomeres are not a glimpse into the future - but definitely an indicator of the circumstances in which an organism lives.
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