Study of European shag shows parental age may affect how long offspring live

Britt J. Heidinger, assistant professor of biological sciences at NDSU, Fargo, has joined colleagues in Scotland to address this question through the study of a long-lived seabird, the European shag. The results appear in "Parental age influences offspring telomere loss," published in Functional Ecology.

According to Heidinger, research in many organisms has shown that offspring produced by older parents often do not live as long, but little is known about why that occurs.

The answer may lie in the offspring's DNA. Or more precisely, in the length of telomeres, which are protective caps at the ends of chromosomes.

"Telomeres function a bit like the plastic caps at the ends of shoelaces and protect the coding DNA from loss during cell division. Telomere loss reduces the lifespan of cells and is thought to be involved in the aging process," Heidinger explained.

Individuals with longer telomeres or slower rates of telomere loss have been shown to have greater longevity in a wide range of species. There also is evidence the offspring of older parents have shorter telomeres, but it is not clear whether this is due to the offspring inheriting shorter telomeres or if their telomere loss during pre- or post-natal growth is higher.

The researchers examined the relationship between the age of the parents and the telomere length of their offspring. They found that when chicks first hatched, there was no effect of parental age on offspring telomere length, suggesting there were no pre-natal effects of parental age. However, chicks produced by older parents had greater telomere loss during nestling growth than chicks produced by younger parents.

The results are consistent with the hypothesis that the age of the parents influences offspring longevity, in part, through its effects on offspring telomere loss during post-natal growth.

"We have previously found that shag chicks that experience higher levels of stress during development have greater telomere loss. These results could have occurred because older parents do not provide as much parental care as younger parents, or because parents that put less effort into raising their chicks live to be older," Heidinger said. "

The study was conducted on a free-living population of European shags (Phalacrocorax aristotelis) that breed on the Isle of May National Nature Reserve in the Firth of Forth, Scotland. The socially monogamous seabirds are long lived, sometimes as much as 22 years. Researchers focused on nests where one of the parent's age was known, as the population of shags in this location has been studied for more than 30 years. In the chicks being studied, researchers collected small blood samples to measure the telomere length of the offspring.

Study results showed that chicks produced by older mothers and fathers had significantly greater telomere loss than chicks produced by younger parents, but the loss appeared to occur during nestling growth, rather than during the pre-natal period. Results also seemed to indicate that the maternal age effect is stronger than the paternal age effect.

Heidinger's fellow researchers include Katherine A. Herborn, Winnie Boner and Pat Monaghan of the University of Glasgow, Scotland; Hanna M.V. Granroth-Wilding of the University of Turku, Finland; and Sarah Burthe, Mark Newell, Sarah Wanless and Francis Daunt of the Centre for Ecology and Hydrology, Edinburgh, Scotland.

Heidinger joined the NDSU faculty in 2013. She earned her bachelor's degree in biology at the University of Minnesota, Duluth, and her doctorate in evolution, ecology and behavior at Indiana University.