How Much Do You Know About Spider Silk?

How much do you know about spider silk? If you were given full use of a world-class laboratory, unlimited resources, with all the physical elements at your disposal, would you be able to manufacture some yourself?

Compare these characteristics of the world’s toughest material with the best that technology can offer:

  • A strand of spider silk long enough to circle the Earth would weigh less than a tennis ball.
  • Spiders excel at recycling: they eat their web once it has served its purpose.
  • Scientists have so far been unable to reproduce the silk-producing machines of spiders in a laboratory, due to the complexity of the protein molecules involved and the consistency of the repetitive DNA sequences.
  • For producing its silk web, spiders have up to eight spinneret glands, excreting on-demand different types of silk: sticky, non-sticky, fine, heavy, depending on the spider’s immediate requirements. These spinnerets can operate independently, but somehow the spider skillfully co-ordinates them to produce the required silk.
  • Spiders produce silk for a number of purposes: attachment, dragline, web frame silk, wrapping, sperm web and egg cocoons, and sticky silk for capturing prey. For example, the spider builds an initial line from which the new web is going to hang — this is not sticky; but the subsequent web is made from quite sticky silk, whilst the silk spun to bundle its prey is a different consistency again.

  • Silk threads are about one-millionth of an inch thick. Spiders can use them singly or in combination to thicken them, using muscles and valves in the necks of the spinnerets.
  • Not all spiders build webs, but all males use silk to spin a sperm web before mating, and all females spin a silk cocoon around their eggs.
  • Gram for gram, spider silk is stronger than steel. Some types of silk are tougher than Kevlar (used in bullet-proof vests).
  • The silk can withstand extreme changes in temperature: from -40 C to 200 C.
  • Spider silk is very elastic. The thread of the Orb-Weaver Spider can stretch up to 20 times its original length.
  • Spiders produce an oily secretion on their legs which, combined with tiny barbs on the bristles of their feet, keeps them from slipping when walking on their own silky webs.
Figure of a spider’s silk producing gland
  • Spiders can produce a metre of silk in less than a second, and scientists still do not know exactly how they do it.
  • Some spiders spin webs over three metres wide.
  • The spider uses a gel substance to create the silk, and this is kept in a neutral pH environment which keeps the proteins from binding and clustering. But when forced into the duct where the silk is made, the environment is acidic, and the proteins begin to bind and “unfold” to create the spider silk.
Silk production as seen through an electron microscope

What do you think? Did these complex machines that baffle modern science arrange themselves into this exquisite formation?


References:

http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001921

The Book of Animal Ignorance: Everything You Think You Know Is Wrong (by John Lloyd and John Mitchinson. Publisher: Harmony 2 Sept. 2008).

http://www.smithsonianmag.com/smithsonian-institution/ask-smithsonian-how-do-spiders-make-webs-180957426/

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0062682

http://rsif.royalsocietypublishing.org/content/12/113/20150633

http://eol.org/pages/1194672/overview

https://www.uaf.edu/files/ces/publications-db/catalog/anr/PMC-10075.pdf

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