Australasian Science Magazine

Scientists have developed the first DNA-based test for estimating the age of humpback whales by examining age-related changes in the DNA of skin samples collected from live whales using biopsy darts.

Dr Simon Jarman of the Australian Antarctic Division said that the new test relied on changes in the methylation of genes involved in the ageing process. “We’ve long known that DNA methylation is involved in processes like sex determination and the development of many cancers, but it has only recently been shown to be involved in the ageing process,” Jarman said. “We used information on age-associated DNA methylation in human and mouse genes to identify similar gene regions in humpback whales. We then developed an assay using three of the most informative methylated genes.”

Estimating age is important for monitoring the recovery of whale populations following commercial whaling. When combined with genetic information about the relatedness of individuals in a population, age data improves methods for estimating the size of whale populations. It is also critical to understanding how the biological characteristics of whales change with age.

Visual ageing of humpback whales is impossible once they are weaned because their size and external features do not change reliably. Age estimates can be made by analysing lipid profiles from blubber samples but these vary depending on the whales’ diet, which depends on their foraging range. Scientists can also identify whales from unique markings on their tail flukes.

“Our new DNA methylation-based test provides a minimally invasive and more reliable test that does not kill the whale, that is less labour intensive than photographic identification, and that can be used on any humpback whale found in any ocean,” Jarman said. “Almost everyone who studies humpback whales collects biopsy sample for population genetic analysis, so this method also fits into established sampling programs.”

The research was published in Molecular Ecology Resources.