Fossilized melanosomes might just be my new favorite subject. Melanosomes are organelles–cell parts–responsible for producing the pigment melanin. These tiny bits of biology can be preserved in fossils, which has led to some fascinating papers. Scientists have now recovered melanosomes from dinosaur fossils, for instance; the pigment allowed researchers to determine–rather than just guess–how certain dinosaurs were colored.
A new study, published online today by Science, reveals another neat use for fossilized melanosomes–tracing the evolutionary history of the penguin. The birds have remarkable feathers, perfectly designed not only to allow the penguins to glide through the water at high speeds but also to insulate them from the breathtaking cold. For these reasons, and others, penguins’ feathers are radically different than those of other birds.
The new research begins to reveal how these multitasking feathers evolved. The scientists studied the 36 million year old fossilized feathers of Inkayacu paracasensis, a newly discovered species of giant penguin that stood five feet tall. From the outside the feathers looked just like those of modern penguins, with the same streamlined shape and dense packing.
But the melanosomes told a different story, revealing that the ancient penguin would have displayed gray and reddish-brown patterning. Today’s penguins, on the other hand, have melanosomes that make them look black.
The findings suggest that the exterior of penguin’s feathers evolved first and that only later did the interior of the feathers, with their melanosomes, change.
Among the most interesting sections of the brief paper is the very end, when the researchers speculate about what could have driven the color change. Previous studies have suggested that melanin can protect feathers from breakage and damage. Penguins swim underwater at incredible speeds (in what’s known as “aquatic flight”) and their feathers must withstand enormous pressures and forces. Birds with more melanin–and, therefore, darker feathers–may have had a survival advantage. That cute black suit that makes us flock to the theaters to see movies about penguins? Perhaps that’s just an unintended–if handsome–side effect.
Reference: Julia A. Clarke, Daniel T. Ksepka, Rodolfo Salas-Gismondi, Ali J. Altamirano, Matthew D. Shawkey, Liliana D’Alba, Jakob Vinther, Thomas J. DeVries, Patrice Baby (2010). Fossil Evidence for Evolution of the Shape and Color of Penguin Feathers. Science : 10.1126/science.1193604
Images: 1. Image courtesy of Science/AAAS 2. Illustration by Katie Browne, U.T. Austin