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Photos by Jelger Herder / Minden
By Alex Viveros
If there is one characteristic feature of daddy’s long legs, it must be their legs. Now scientists have shortened the legs of a species – and turned them into food-handling limbs – by altering the DNA expression of arachnids.
To determine which genes cause the development of long legs in these spider parents, the researchers assembled the first genome project from Phalangium opilio and looked at three genes that serve as a model for different parts of the body. When they traced the activity of two of these genes, they found that they were activated in the legs of embryos under a microscope. Then they used RNA interference – a technique that reduces gene expression – to bring them down in hundreds of P. opilio embryos. When they did, they saw that among the surviving newborns, six of the eight legs were about half their normal size, they report today in the Proceedings of the Royal Society B: Biological Sciences. In addition, they had transformed into short pedipalps, a type of limb for handling food.
When the researchers destroyed a third developmental gene, believed to help build embryonic legs, the limbs didn’t turn into pedipalps, but they did get shorter. They also lost their tarsomers, a set of around 100 knuckle-like joints that can wrap around sticks like a monkey’s tail. Similar transformations have been observed in fruit flies, which may give scientists a clue as to how P. opiliothe legs of may have evolved.
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