The Origin Of Orbs - Science News

In the February 25 Issue:

The origin of orbs

Spectacular web designs trace back to a single spider origin

By Nick Bascom

Web edition : Thursday, November 3rd, 2011

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The traditional orb web (shown above with a spider from the family Araneidae) is characterized by radial spokes of spider silk connected by concentric circles of the same sticky thread. This pattern may have been the original design used by prehistoric orb weaving ancestors.Gustavo Hormiga

Spiders responsible for the majestic feats of architecture called orb webs may have evolutionarily diverged from a single weaver. Though modern-day spiders spin silken snares of many different shapes and sizes, arachnids belonging to the Orbiculariae taxon — the orb weavers — can most likely trace their ancestry to a web designer of the prehistoric kind, an international team of researchers reports November 2 in Proceedings of the Royal Society B.

To learn more about the evolution of orb weavers and paint a clearer picture of their web-decorated family tree, the scientists examined molecular differences in six genes across 300 species of spiders. The number of differences in the DNA of related species corresponds with how much time has transpired since they diverged from a common ancestor.

Based on this molecular data, ancestors of orb-weaving spiders first crafted their sticky traps around 200 million years ago, suggest zoologist Dimitar Dimitrov, of the University of Copenhagen and George Washington University in Washington, D.C., and colleagues. Although the orb weavers rapidly evolved new web materials (such as stickier, more viscous silk) and new web designs (such as sheet and cobwebs) to more effectively capture insect prey, the various snares probably derive from a single original design plan.

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Comments 3

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Except that the apparent design isn't "planned" but evolved as a function too, natch.

Torbjörn Larsson, OM

Nov. 4, 2011 at 12:33pm
The concluding sentence could have been better written to say "...the various snares probably derive from a single original pattern." To say that the original pattern was "designed" or "planned" infers something that is beyond the scope of the evidence and is beyond the ability of science to answer.

Robert Woodman

Nov. 7, 2011 at 9:16am
The author's use of the phrase "web designer" was likely a play on words, referencing modern technology. In any case, a spider's web is designed, at least in the very short-term. Natural selection would determine the behavior of the spider designing the web. The web itself is not a direct result of evolution, but rather an indirect result of behavioral evolution. It remains to be seen exactly how much planning goes into making a web, but I would expect spiders at least take into consideration environmental variables before beginning construction.

Adam Flanders

Nov. 14, 2011 at 9:36am

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Citations & References :

D. Dimitrov et al. Tangled in a sparse spider web: single origin of orb weavers and their spinning work unraveled by denser taxonomic sampling. Proceedings of the Royal Society B.doi: 10.1098/rspb.2011.2011. Available online: [Go to]

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