As with most discoveries, the question is how we can take advantage of
this? Can the structures be duplicated for use in solar cells? Maybe
grown for organic based solar power (non-tree)? I guess I'll just have
to wait 10 or 20 years till the discovery is actually used in
something beyond the lab (if at all).


The Oriental hornet has a unique ability to harvest solar energy,
scientists have discovered.

The large wasp species has a special structure in its abdomen that
traps the sun's rays, and a special pigment that harvests the energy
they contain.

The discovery helps explain why these hornets have a large yellow
stripe across their body and why they become more active as the day
gets hotter.

It also changes our understanding of how insect metabolism can work.



The discovery, reported in the journal Naturwissenschaften, was made
by a team of researchers working in Israel and the UK, led by Dr
Marian Plotkin of Tel-Aviv University.

Wasps are usually most active in the early morning, when they are
around twice as active as at any other point in the day.

Oriental hornets ( Vespa orientalis ), which range from the Near East
to India, are most active in the middle of the day.

Scientists have also long observed that Oriental hornet workers, which
dig out nests underground, correlate their digging activity with the
intensity of sunlight.

However, it was unclear why these Oriental hornets behave in this way.

Warming up

That was until one biologist, the late Professor Jacob S Ishay,
proposed that the insects may somehow be capable of harvesting solar
radiation.

Dr Plotkin's team has now tested this hypothesis, with remarkable results.

Using an atomic force microscope, they examined the fine structure of
the hornet's cuticle, hard layers of which form the insect's outer
body, or exoskeleton.

The part of the cuticle coloured brown is made from an array of
grooves, with a height of just 160 nanometres.

The structure of the yellow part of the hornet's body is different.

This is made from a series of oval-shaped protrusions, each containing
a pinhole-sized depression. Each protrusion is just 50nm tall and
interlocks with another.

Further tests revealed what these structures do.

Essentially, say the researchers, they stop light being reflected off
the hornet's body. Instead the light is trapped, and harvested for
energy.

The brown part of the insect's body has the best anti-reflectance
properties, helping to split any sunlight that falls upon it into
several beams travelling in different directions.

The cuticle also contains a second thin sheet-like structure, with a
series of sheets stacked on top of each other, with decreasing
thickness from top to bottom.

Stacked together in every layer are rod-like structures composed of
chains of a polymer called chitin. These rods are embedded in a
protein matrix.

This intricate structure further serves to trap light within the
cuticle, forcing it to bounce between different layers.

Capturing the sun

But the ability of the hornets to harvest solar energy does not stop there.

Within this cuticle is a pigment that actually captures the energy of
the sun's rays.

"The pigment melanin gives the hornet its dominant brown colour. The
pigment xanthopterin, in the head and abdomen in a form of stripes and
bands, gives the Oriental hornet its bright yellow colour," explains
Dr Plotkin.

"Xanthopterin works as a light harvesting molecule transforming light
into electrical energy."

The hornets' ability to convert sunlight in this way could explain why
they become more active during the middle of the day, when the light
intensity is highest.

"We assume that some of the energy is transformed in a
photo-biochemical process which aids the hornets with their energy
demanding digging activity," Dr Plotkin told the BBC.

The solar-powered hornets have one further unique claim.

Until now, insects were thought to perform metabolism in an organ
known as the fat body, which performs a similar function to the human
liver.

Most of the fat body is in an insect's abdomen surrounding the gut,
where it can quickly take up absorbed nutrients, though some is
scattered elsewhere.

"We have found that the main metabolic activity in the Oriental hornet
is actually in the yellow pigment layer," says Dr Plotkin.


Matt Walker
Editor, Earth News
http://news.bbc.co.uk/earth/hi/earth_news/newsid_9254000/9254445.stm

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