Friday, 5 July 2013

Self-cleaning eggs of Guillemot

According to new research, guillemot eggs have special structures on their shells which makes them self-cleaning. The study began after scientists noticed the liquid-repelling properties of a batch of eggs which had water spilled onto them. Further analysis revealed tiny cone-shaped structures on the eggs' shells were responsible for this property. Dr Steven Portugal from the Royal Veterinary College in London who conducted the research said that the project started with a "minor spillage" in the lab. "I accidentally spilled distilled water over a batch of eggs," Dr Portugal recalled.

"And I noticed that the eggs from the guillemots stood out in terms of how the water droplets reacted on the surface. They formed little droplets,- they didn't run down the egg." The formation of water drops into perfect spheres is typical of hydrophobic or water-hating surfaces. The best-known example of this in nature is a lotus leaf. "It's been copied in engineering, because it's self-cleaning" said Dr Portugal. "These spheres of water fall off when they're knocked and take all the dirt with them."

To find out what was responsible for this property in guillemot eggs, the scientist examined the egg shells using a highly sensitive laser scanning microscope. "We saw these structures, nano-scale cones," the scientist explained. "With the microscope, the egg surface looked like the Himalayas." When Dr Portugal went on to examine the eggs of other species of seabird that nested in similar habitats, he discovered that the structures were absent. This suggests that guillemot eggs have evolved these specialised surfaces in order help with their perilous cliff-side environment. Guillemots are unusual in that they don't bother with a nest at all, they just dump the eggs on the cliff face," explained Dr Portugal.

"And they're crowded into these dense colonies. So they need to have a mechanism for coping with the salt spray coming off the sea and for dealing with the fact that there's a lot of detritus around [from other birds]. That's what these structures do." These self-cleaning egg shells allow the embryos inside to breathe, letting oxygen and carbon dioxide pass through the shell unimpeded by salt or dirt. Scanning electron microscopy revealed unique cone like structures.

The structures also make the egg shells rougher, and Dr Portugal is currently investigating whether this helps to prevent them from tumbling off the cliffs. Guillemots are members of the auk family and gather in large colonies around the coast of the UK. They do not have nests but lay conical eggs which roll less so they remain safe on cliff edges.

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