Scientists manipulating genes have created fruit flies with eyes on their wings, legs or even on the tips of their antennae.
The researchers said their demonstration suggests they have found a gene that may be a master control for the entire complex formation of the insect eye.A researcher not involved in the project called the findings "remarkable."
In a report published in Friday's journal Science, researchers Georg Halder, Patrick Callaerts and Walter J. Gehring said the out-of-place eyes contained the entire eye structures, including cornea, pigment and photoreceptors, the cells that respond to light.
Magnified views of the outside of the extra eyes show they have the compound structure and bristles that are found on normal fruit fly eyes.
"The eye structures induced on the legs were on average smaller than the ones on antennae or wings, but nevertheless appeared to have a relatively normal organization," the Swiss scientists report.
Gehring said the misplaced antennae eyes looked "like little crab eyes" on stalks projecting from the fly head.
However, the University of Basel researchers said it was unknown if the eyes were functional or if they sent signals indicating the detection of light to the insect brain.
The insect's eye control gene, called eyeless, has a counterpart in mice and in humans, suggesting that genes that play a key role in formation of eyes may have had a common evolutionary ancestor, the scientists report.
In mice, the gene is called small eye because earlier studies showed that its manipulation would cause mice to grow small eyes or none at all.
In humans, the eye gene is called Aniridia. Mutations of one copy of this gene cause defects in various parts of the eye, including the iris, lens and cornea.
In a report in Science, Gerald Rubin of the University of California, Berkeley, marveled at the Swiss research.
"It is really remarkable that you can take a tissue that would normally make a wing or an antenna and by turning on one gene make that into a complex thing like the eye," he wrote. "This is like someone finding a gene that could turn a kidney into a liver."