Chemical weapon in spider silk repels ant attack: study

November 23, 2011
Nephila antipodiana
Nephila antipodiana. Image credit: (by Joseph K H Koh)

Researchers have shown for the first time how Golden orb web spiders (Nephila antipodiana) add a chemical to their web silk to repel invading ants.

The finding adds a chemical defense to the impressive properties of spider , already known to be very strong, elastic and adhesive, and may provide new opportunities for pesticide design.

The study was led by researchers from the National University of Singapore (NUS) and the University of Melbourne, and is published in the journal today [Wednesday, 23 November 2011].

Associate Professor Daiqin Li, who led the team at the National University of Singapore, said that ants rarely occur on the web of spiders, despite their abundance, so his team set out to discover why.

"We found that large Golden orb web spiders add a defensive alkaloid chemical onto the silk, which stops the ants from walking onto the web when they come into contact with it," said Assoc Prof Li from the Department of Biological Sciences, NUS.

Professor Mark Elgar from the University of Melbourne's Department of Zoology said the team was impressed by the strength of the ant repellent in the web silk.

"The type of chemical deterrent found in the is known as a pyrrolidine alkaloid, which acts as a predator deterrent in many species of ants, and ," Prof Elgar said.

The team found that only large Golden orb web spiders produce the defensive compound, suggesting that the younger, smaller spiders could rely on their thinner web silk to physically prevent ants being able to climb into their webs.

They made the discovery by allowing the Golden orb web spider to spin webs in the lab and then analyzing the compounds in the silk. Once the defensive alkaloid compound was identified, the researchers observed the behaviour of ants in its presence.

"The orb spider is potentially vulnerable to attack from groups of ants while sitting in its web waiting for prey, so the chemical defense in web silk may have evolved to not only protect the spider, but to reduce the time and energy that would otherwise be required to chase away invading ," said Prof Elgar.

The Golden orb web spider is typically found in the forests of Australia, Asia, Africa and America.

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5 / 5 (1) Nov 23, 2011
How wonderful for the spider that its ancestors were able to divine what chemical kept ants away!!!

You really don't have any clue how mutation and selection works?

A quick primer:
Mutation in the DNA is (more or less) random. Many things don't work (and the so mutated specimens die). Occasionally a mutation does work and this speciemen survives and reproduces. It's descendants carry the mutation and quickly outbreed the ones that don't have it.

Not all mutations need to be done at the same time. Maybe the first mutation was production of the alkaloid. Millenia later another mutation added the ability to let this stuff stick to webs.

Just like with the eye: having an eye that only distinguishes light from dark is already an advantage over blind competitors. Later incoroprating a very rudimentary lens is an advantage over the ones that merely have the dark/light ability. Stuff adds up over millions of years until you get the wonderfully complex structures we have today.
The Singularity
not rated yet Nov 23, 2011
The image is mildy disturbing & should be labelled as so.
not rated yet Nov 23, 2011
I find this kind of hidden, natural warfare fascinating. I really do. Nature is an amazing source of invention.
not rated yet Nov 23, 2011
Thanks again for proving you don't know how selection works, kevin. The mutation isn't a response to the environmental/predatory/sexual selection pressure. Tard.

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