AN international team led by BGI-Research has shed new light on evolutionary pathways that allowed penguins to transition back into aquatic environment, particularly in extreme cold like the seas around Antarctica, Shenzhen Economic Daily reported Thursday.

The article, titled “Genomic insights into the secondary aquatic transition of penguins,” was published in Nature Communications on Tuesday.

Using genomes of all living and recently extinct penguin species, as well as the morphology of long-extinct species, researchers reconstructed over 60 million years of penguins’ evolutionary history, aquatic ecology and population history.

One of the study’s key findings is that global cooling and major ocean currents appear to have been the main drivers of penguin diversification and biogeographic patterns.

In addition, the study provided some unexpected results. Penguins and their sister group Procellariiformes (an order of seabirds comprising albatrosses and petrels), have the lowest evolutionary rates yet detected in birds. This finding may represent the culmination of a gradual slowdown associated with an increasingly aquatic lifestyle.

“Our study indicates that the extreme environment in Antarctica has brought greater pressures to high latitude penguins,” said joint first author Zhou Chengran from BGI-Research. “Climatic fluctuations have further promoted the migration, evolution and diversification of penguins, and to a certain extent, also promoted the adaptation of high latitude species to extreme environments.”

As penguins became increasingly adapted to a flightless diving ecology, they encountered novel selection pressures that required modifications to their locomotory strategy, thermoregulation, sensory perception and diet, according to the study.

Penguins exhibit specializations for vision in dim, blue-green marine environments as they frequently forage in low light.

The highly specialized seabirds also function under hypoxic conditions during deep dives in part via myoglobin concentration and utilizing anaerobic metabolism, which enables them to make more efficient use of oxygen in their blood to prolong diving.  (Zhang Yu)