Sixty million years of information about Penguins

Contrary to popular belief, penguins did not originate in the Antarctic. They originated in microcontinent called Zealand (around present-day New Zealand) and from that starting point, some 60 million years ago, they began to disperse, to evolve, to transform. Pablo Borboroglu is a CONICET researcher at the Center for the Study of Marine Systems (CESIMAR, CONICET) and co-author of a recently published international study that analyzes, over time, the adaptations that allowed these animals to live in environments with the most extreme conditions on the planet. For this study, genetic samples of current penguins and fossil species were analyzed to learn in detail their origin and evolution. The results were published in Nature Communications.

“The geneticists identified the DNA segments that determine the evolutionary characteristics related to vision, taste of prey, in the ability to oxygenate, to remain in apnea under water, the ability to generate fat, to resist cold. This type of fossil analysis included all penguin species, not just the eighteen that currently exist. Throughout history, penguins of many shapes and sizes have inhabited the planet, including one that is one of the oldest ones of New Zealand, which they called the Monster Penguin, an animal that weighed more than 80 kilos and is estimated to have reached 1.8 meters. Seventy-five percent of the species that existed are already extinct. Three quarters of the history of penguins no longer exists. Many species collapsed because of climate change but they can still give us a lot of information,” Borboroglu explains.

Although there are previous studies that focused on the adaptive changes of penguins, this study includes a large number of genes from extinct species that will provide information on their adaptations over time. “Sampling of fossil penguins is crucial for understanding the environmental context, improving phylogenetic resolution and dating accuracy, and reconstructing biogeographical events,” says Borboroglu.

Currently, penguins spend more that eighty percent of their lives in the water. The bodily adaptations that explain this ability come from the past. Penguins had already lost their ability to fly 60 million years ago, before the information of the polar ice caps. Since then, their life characteristics have been shaped by rising and falling temperatures, and their bodies are highly specialized for some of the most extreme conditions on Earth.

“Some of the genes that were analyzed are related to vision and how it was adapted to look accurately underwater and facilitate the capture of prey. They can observe a wide range of ultraviolet colors that we do not see, and they have, on the other hand, a more limited possibility of seeing other colors such as red, the first color that stops being seen in the ocean. Another of the modifications is linked to taste. They can detect salty and bitter tastes, but not sweet or sour ones. This is related to the diet they eat. All these characteristics tend to improve the efficiency of these animals under the sea. An emperor penguin, for example, can stay underwater for up to twenty-three minutes and dive up to five hundred meters deep”, describes the researcher.

Despite all the changes that these animals have been adopted and that have made them, possibly, the most uniquely specialized birds of all the existing ones, studies indicate that their possibilities of adaptation have diminished. “60 million years ago the rate of penguin evolution was very high but it slowed down. This is related to the sea surface temperature. At times when it was warmer, the rate dropped and vice versa. Larger penguins also had a higher rate because they generally live or have lived in more extreme environments. Penguins currently have the lowest rate of evolution of all birds. At the rate of environmental change taking place, this could present a conservation problem for penguins. That is why this type of study is of vital importance to know more and more precisely the adaptive capacities that these animals were acquiring and to think about them in the context of the challenges of the present.