How baleen whales have adapted over the past 50 million years

The new study, published in the international journal Gene, explores the key genetic adaptations of these diverse whale species around the world's vast oceans -- giving new insights into the risks and opportunities for their survival.

"We actually know very little about the genetic diversity of modern whales, compared to terrestrial animals, so these insights give fresh information about their radiation and changes over the past 50 million years," says PhD candidate Gabrielle Genty, from the College of Science and Engineering, Flinders University.

The study helps to explain the intriguing mammals -- from the gigantism of the largest blue and fin whales, to the diving and migratory abilities of other baleen whales, including humpbacks, minkes and gray whales.

While genes linked to survival, ageing, movement, immunity and reproduction were highlighted, future adaptations will need to respond to climate change and other threats including marine pollution and diseases, researchers say.

"For example, we found genes that improve immunity have been important for the largest species, fin whales and the world's largest animal, the blue whale," says Ms Genty, from the Flinders Cetacean Ecology, Behaviour and Evolution Lab (CEBEL) and Molecular Ecology Lab at Flinders University (MELFU).

"Their additional adaptations related to the immune system may help these species achieve their large size without suffering detrimental health issues like tumours and cancer, which are typically associated with increased body size and rapid cell generation."

The research used a dataset of 10,159 genes, across 15 cetacean species and two terrestrial species -- hippos and cows (Hippopotamus amphibius and Bos taurus) -- which are the considered the closest land relatives of whales.

Baleen whales are highly mobile and pelagic, so studying them is challenging.

Senior coauthor, Flinders University Associate Professor Luciana Möller, says cetaceans (whales, dolphins and porpoises) have diversified into myriad groups since they left land for their aquatic world in history.

This diversification resulted in a minimum of 89 main species, divided into two main suborders: 74 belonging to Odontoceti (toothed whales, dolphins and porpoises) and 15 to Mysticeti (baleen whales), which possess baleen plates for filter-feeding.