'Blind' golden moles found to be world's first iridescent mammal

Last Updated: Wed, Jan 25, 2012 11:50 hrs

Scientists have revealed that golden moles are the first known iridescent mammals.

Iridescence - a lustrous rainbow-like play of colour caused by differential refraction of light waves - has just been detected in the fur of golden moles.

Aside from the "eye shine" of nocturnal mammals, seen when a headlight or flashlight strikes their eyes, the discovery marks the first known instance of iridescence in a mammal.

Another surprising finding of the study is that the golden moles are completely blind, so they cannot even see their gorgeous fur.

"It is densely packed and silky, and has an almost metallic, shiny appearance with subtle hints of colours ranging between species from blue to green," Matthew Shawkey, co-author of the study, told Discovery News.

For the study, the scientists pulled hairs from specimens of four golden mole species. Using high tech equipment, such as scanning electron microscopy and transmission electron microscopy, the researchers analysed the structure of the hairs, down to their smallest elements.

They determined that the hairs are indeed luminescent. They further discovered that each hair has a flattened shape with reduced cuticular scales that provide a broad and smooth surface for light reflection.

The scales form multiple layers of light and dark materials of consistent thickness, very similar to those seen in iridescent beetles.

Optical modelling suggests that the multiple layers act as reflectors that produce colour through interference with light. The sensitivity of this mechanism to slight changes in layer thickness and number explains colour variability.

But why blind animals would have such eye-catching fur remains a mystery.

Ancestors of the moles were sighted, so it's possible that the iridescence is a carryover from those times.

"However, the moles have diverged considerably from these ancestors so there had to be some selection pressure other than communication to keep their colour intact," Shawkey said.

Another possibility is that the fur somehow wards off the mole's sighted predators. But Shawkey said shiny fur "would seem to make them more conspicuous," doing just the opposite.

The moles are not poisonous, so the coloration does not serve as a warning to other animals.

The researchers instead think that iridescence may be a byproduct of the fur's composition, since the structure also streamlines the mole's profile and creates less turbulence underground, permitting the animals to move more easily through dirt and sand.

The study was published in the latest Royal Society Biology Letters. (ANI)