Spider Silk Admired, Not Duplicated
Spiders still maintain the edge in a technology humans want: a material that absorbs huge amounts of energy without breaking. The dragline silk spun by spiders is extremely robust – ounce for ounce stronger than steel, yet more flexible than Kevlar. If a web the size of a football field could be erected in the air with strands one centimeter thick arranged in concentric circles 4 cm apart, it could stop a jumbo jet in flight. (We won’t try to envision a passenger’s view of the spider sneaking up on the captured plane. Whoops, too late.)
Fascinating facts about spider silk made the cover story of Science News (171:15, p. 231, 04/14/2007). Aimee Cunningham told about teams like that of Nikola Kojic (MIT) that are trying to replicate this ideal material but have not yet succeeded in matching its strength. Human versions require high temperatures, high pressures and toxic substances to make. Your humble garden spider has no such limitations:
In contrast, natural spider silk is produced at room temperature with water as a solvent, says Chris Holland, a zoologist at the University of Oxford in England. “It’s made in the spider, and with the spider eating flies. That produces a fiber that we can’t even come close to.”
The formula for synthetic dragline silk is a prize humans eagerly seek. Such a tough and flexible material would find many applications, from bulletproof vests to suspension cables for bridges. Maybe even Spiderman toys will come from it. “The spider hasn’t given us all the secrets,” said one researcher.
Somehow, the spider extrudes a silk dope through ducts in its abdomen, and this goop solidifies into a strand that is stretchy and very tough. “A silk thread contains hundreds of thousands of protein chains, each of which folds on its own and also arranges itself among other chains in the fiber.” One researcher found that repeating units are able to snap together like Lego blocks.
Even more amazing, spiders spin seven kinds of silk from the same machinery. Dragline silk, forming the spokes of the web, absorbs the brunt of the energy. Capture-spiral silk is stretchy and sticky. Other forms are used to wrap the prey, coat the egg sacs and perform other functions. One team found that the prey-wrapping silk is up to three times tougher than dragline silk. This adds drama to that scene of Shelob’s lair in The Return of the King.
At this point, the R&D of spider technology is still in the R stage. Spiderman wannabees will probably not find webshooters under the tree this year. But even though the researchers interviewed for the article stand in awe of spider silk, they did not shy away from speculating about how evolution gave the spider a technology our brightest minds cannot emulate. “Spiders and silkworms evolved the capacity to spin silk independently of each other,” said one:
The dopes contain different proteins, and the resulting fibers have distinct properties. Yet “what we see is that the flow properties are very similar,” [Chris] Holland [Oxford] says. Despite their differences, the spider and silkworm “use similar tricks,” he continues. “This gives fantastic insight into how silk production has evolved and how the production of an energy-efficient, high-performance fiber is made by nature.”
Not only that, it happened a long, long, time ago: “Spiders have been spinning these silks for almost 400 million years.” No questions asked.
The evolution-talk ruined an otherwise great article. Notice that the Darwin storytelling was absolutely useless. Evolution was assumed without evidence and contributed nothing to helping the scientists on their quest to reverse-engineer the technology.
Most people detest spiders and find them creepy or scary. Let’s teach our kids to admire them and respect them, along with ants, honeybees and the many other critters around us. Some of our fellow denizens we need to admire at a distance, and yes, it’s OK to keep them out of the house. Spiders don’t mean to invade your space; they just wander and get disoriented sometimes and need a little help. Maybe instead of stepping on every spider you see, you should teach kids to scoop them up and let them play in their own space outside. Your reporter once watched a four-inch-wide hairy mygalomorph come strutting into the bedroom just before lights out. Mutually startled, the human jumped up and the spider ran under the bed. The spider needed a little help for about half an hour getting rediscovered and assisted into a more suitable habitat. All lived happily ever after.
Help children observe the wonderful ways spiders weave their webs. Have you ever witnessed the whole web construction process? The material is amazing enough, but watching how the spider creates the pattern is a lot of fun. When they wrap their prey, it shouldn’t seem that different from what we do with our food. Think how repulsed a hen in a Far Side Horror Movie would be watching humans cut up a rotisserie chicken, shrink-wrap the pieces and put them in the refrigerator. It’s all in the point of view. What do you want, a yard full of flies? Spiders do us a service. By capturing, stunning and wrapping their food, spiders keep their meat fresh and help maintain the balance in nature. Their ability to turn fly guts into techno-silk should not be minimized. Don’t feel slighted. You can take barbecue chicken and transform it into cerebral cortex.