The Seychelles warbler is the perfect candidate for studying inbreeding.
Image credit: UAE
The science of aging is a relatively young field, and there are many mysteries yet to uncover.
Certain genetic markers have been identified that correlate with aging, but how they behave in a population and the factors that influence them are not yet fully understood.
In an effort to uncover further detail about the genetic basis of aging, a team of scientists from the University of East Anglia (UAE), United Kingdom, took a look at the genetics of birds called Seychelles warblers.
The team set out to investigate the role, if any, of inbreeding on cellular aging.
The small size of the warbler population in the Seychelles makes them ideal for the study of inbreeding. Because the island is geographically isolated, the birds are confined and can not interact with populations in other regions.
An estimated 5 percent of this bird population mate with first-order relatives (parents, siblings, or offspring).
Aging and telomeres
Telomeres are protectors of the genetic code and consist of repeated sequences that hang from both ends of all chromosomes. They prevent DNA sequences from being eroded over time.
Telomeres also prevent sections of DNA from sticking together and jumbling up the sequence. Cells in most species, including humans, use this system.
Each time a cell divides, the telomere gets shorter, and, over the years, telomeres slowly shrink in size. The older we are, the shorter our protective telomeres. Shorter telomeres are associated with increased risk of disease and a shorter lifespan.
Some refer to telomere length as a biological clock determining the lifespan of a cell or, indeed, an individual.
"Telomeres are a bit like the hard plastic ends of a boot lace. Over time, they get broken down and become shorter because they absorb all the damage experienced during life. The rate at which this happens reflects how much stress the body is under - and, importantly, how long it can continue to function."
Lead author Kat Bebbington
Telomere length is affected by a number of factors, including smoking, obesity, traffic pollution, and stress. With the results of this latest study, researchers now believe that inbreeding could be another factor that reduces telomere size.
Seychelles warblers and their telomeres
The research team, headed up by Prof. David S. Richardson, studied the telomeres of Seychelles warblers (Acrocephalus sechellensis) based on Cousin Island. This particular island has a population of just 320 individuals.
Over the course of 14 years, the team took 1,064 DNA samples from 592 birds. Throughout the duration of the study, conditions on the island - such as weather and food availability - were continually monitored.
The results, published in Molecular Ecology this week, show that the more inbred birds had significantly shorter telomeres; they also noted that this shortening was more pronounced in stressful times, for instance, when food was in short supply.
"Inbred animals are more susceptible to disease or poorly developed because they don't have much variation in the genes they carry, plus whenever life gets difficult, they can't cope as well outbred animals."
Additionally, an interesting cross-generation effect was noted. If the mother was inbred, the offspring also had shortened telomeres. This might be because the mothers were less able to provide their offspring with the best level of care, either during the egg incubation phase, or when feeding the young bird.
It is challenging to understand the impact of inbreeding on any given population. Its effects can be masked by a number of factors, including the quality of their habitat and diet.
This research is particularly important for species that are on the decline. For some animals, captive breeding programs are their only lifeline, and to be able to monitor the effects of inbreeding on premature aging could help protect important populations from declining health.