Thursday, 17 November 2011

The Colouration Of Ancient Moths

The colouration of the ancient lepidopterans, according to Dr McNamara
In recent years, new fossils and powerful new analysis techniques have allowed palaeontologists to reconstruct the colours and patterning of prehistoric beasts. Creatures such as Anchiornis, with its beautiful white and black bands of feathers and resplendent orange crest or smaller organisms such as ancient beetles, complete with iridescent green and blue carapaces.

Some of the most famous fossils which still display colouration come from the 47 million year old Messel Pits, in Germany, whose oil shale deposits produce specimens of the highest quality.

Over 90% of the organism is present, including soft tissues and subtle chemical traces. It is the chemical traces in particular which aid preservation. The Messel Pits' ancient, alluvial sediment also yields other arthropods, and moths. These are a relatively common find, as the anoxic, oil rich waters preserve the delicate wings in great detail.

Now palaeontologists have revealed the colouration of these ancient creatures. A study conducted by Dr Maria McNamara, famous for her work on the colours of ancient arthropods, has revealed a new method of hue preservation within the moths. Instead of ancient pigment organelles remaining within the shells, the moths possessed a series of patterned scales which bent and reflected light, producing a vivid display of colour. The brightest hues in nature are created in this way.

McNamara found that the moths' body was a light brown colour, while the largest areas of the wing were green, with deep, azure-blue edges. These would have provided camouflage amongst the leaves that made up the Messel lake jungle. The colours also helped protect the moth in another way: the closest relatives of the prehistoric lepidopterans today are Forester moths which feed on nectar. If the ancient examples also fed on flowers, then their coloured wings would have made them stand out.

Forester moths produce cyanide in glands under their skin, making them repellent to taste and toxic to small creatures. The bright colouration in its ancient relative, therefore, may have served as a warning that it was not a viable meal. 'Reconstructing the original colours of ancient animals gives us really good insights into their behaviour' said McNamara. 'These moth fossils hint that we can even do this for fossils that don't have obvious colour.'