Blue-footed booby (Sula nebouxii) performing the species' famous courtship dance.
Credit: Wikimedia
BRISBANE: The first genetic evidence of biological ageing in a population of blue-footed boobies has been identified, disproving the assumption that wild animals die before their DNA suffers from age damage.
The study, published in The Journal of Evolutionary Biology, challenges the idea that the germ line DNA (DNA containing inherited material that is passed on to offspring) of wild animals is protected against damaging agents due to their shorter life expectancies.
"Senescence (or biological ageing) in the germ line can be passed on to the next generation of the animal in the form of DNA damage," said lead author Alberto Velando from the Ecology and Animal Biology Department of the University of Vigo, in Spain.
"It was always thought [to be] something particular to humans and domestic animals, because we have an extended life expectancy," he added, stating that we now know that biological ageing affects the reproductive and living capacity of wild animals as well.
Senior citizens gone wild
Old age in humans and domestic animals can cause genetic difficulties when it comes to reproduction. Studies have shown that human children are more likely to suffer from genetic defects if their father is over 50 years old, due to the DNA damage that occurs in the germ line DNA as the person ages.
Previously, scientists had assumed that wild animals are exempt from this risk as they were likely to succumb to predators or disease before reaching old age.
However, Velando and his colleagues have found that a population of blue-footed boobies (Sula Nebouxii) - a long-living, blue-footed species of seabird from the Pacific coasts of Mexico, the Galapagos Islands and Peru - is showing signs of senescence and DNA damage in the germ line.
"Many biologists thought that animals could not reach senescence in the wild. But we have found that senescence is a very important factor for genetic variation in nature," said Velando.
Germ line not damage-free
Sperm DNA in the germ cells are vulnerable to DNA damage due to the many divisions they undergo. A major type of DNA damage is oxidative stress, where there is a loss of single bases, resulting in lesions known as apurinic/apyrimidinic (AP) sites, which impede further DNA synthesis.
In this study, the researchers used a database containing over 20 years of records relating to a breeding colony on Isla Isabel, Nayarit, Mexico, classifying a selection of males as either middle aged (3-10 years old) or senescent (over 10 years old), and measured the dullness of their foot colour - a visual indication of age - and the amount of AP sites in their sperm DNA.
The results showed for the first time that the booby's germ line is not damage-free. "The DNA of the sperm of older individuals is damaged," said Velando. "This means their offspring have a greater likelihood of suffering from congenital illnesses."
