Spider man at STRI

Dr. Fritz Vollrath studied as graduate student and did post-doctoral work at Barro Colorado Island, but the German scientist, now affiliated with Oxford University, hadn’t been back to Panama in 20 years. He’s back now, and on February 10 he addressed an audience at the Smithsonian Tropical Research Center’s Tupper Auditorium on the subject about which he is one of the world’s top experts, spider webs.

Not all spiders build webs, Vollrath noted, but “they all make silk --- this is what ties spiders together.” Spider silk, he said, “is very strong and very flexible.” When compared to steel cables on the basis of strength for weight, spider silk is six times stronger. When one compares the material with kevlar --- the stuff of which modern bulletproof vests are made --- spider silk is eight times more extensible. Spider silk is also stronger than the silk with which butterflies and moths make their cocoons.

Spider silk “is tougher than anything man can make,” Vollrath pointed out, and thus a subject of interest not only to biologists but also to industry. Thus at Oxford he and his colleagues are trying to copy spider silk production and develop a robot that can make a web like a spider’s.

It’s a complicated multidisciplinary problem. There is the biochemistry involved in the production of spider silk’s prions --- organic molecules in the class of those that cause mad cow disease and Alzheimer’s. There are the physics and architectural aspects of web building. There are the behavioral aspects of how spider makes and maintains his or her web. To further complicate matters, one individual spider can produce several different types of silk from several different glands, and one class of spider silks acts as neural transmitters.

Thus a web not only expands gives a spider the ability to reach and grab prey beyond itself, but it may also allow the arachnid’s nervous system to extent its sensory perceptions. “Spiders have found a way to extend their body morphology by orders of magnitude,” Vollrath concluded.

Webs are of interest not only for their material, but also as models of behavior that are “frozen in time.” Any spider web will have involved such decisions as choice of site, the way it is used for hunting, when it should be mended and when it should be abandoned, at what point the web should be taken down on a windy day and how it should be designed.

Spider webs can also be used to study the horrors of drug abuse. Vollrath showed the audience photos of the work of drugged spiders --- the one produced under the influence of LSD was a neat geometrical spiral apt to catch a delicious fly for dinner, while the web made by the spider who was doped up on caffeine was chaotic and probably of little use for hunting.

Finally, there are the potential industrial applications. Spider silk is extruded rather than spun, with flexible expansion joints created within the arachnids’ bodies. “If you look at spider silk as an energy absorption system,” Vollrath pointed out, “you will have found a general model that applies to all polymers.” At this point, he added, more is known about spider silk than about polymers --- the long molecular chains of critical importance in the production of advanced plastics --- that chemists create in laboratories. Thus the basic scientific research that spider men like Vollrath are doing holds the possibilities of lighter, stronger, more flexible and cheaper materials for a wide range of manufacturing uses.

Also in this section:
Spider man talks to STRI about silk
Embera herbalists want to show their skills
Drought resistance and plant distribution
Making pregnancy safer

science

Spider man back at STRI after 20 years