Juniper Times

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Arachnid Alchemy – Golden Orb Spiders

This summer has certainly been a time of plenty, along with the abundant flocks of White Storks we are witnessing this year, there are also a fair number of Golden Orb Spiders. Their vast golden webs span almost every available gap between trees and shrubs. Reaching great vertical heights and stretching across distances of up to 5 m, these strong spider webs form an almost continuous network of yellow silk ready to ensnare any insect, bird or bat that is on the wing. The golden silk is thought to attract pollinators such as bees.

The big brightly coloured spider in the web is the female Nephila. She may measure 15-30 mm in length while the male is only 5 mm and weighs one thousandth of the female’s weight. A web of this magnitude must require constant maintenance. The weaving of a web takes up a lot of the spider resources and orb spiders tend to eat the silk of any damaged section of web to absorb and utilize the protein. The male of this species does not produce silk but what he lacks in size and in the home maintenance department, he more than makes up for with courage and ingenuity. The female will often eat the tiny male after copulation. Where possible he presents a meal to her and while she is feeding he will copulate with his preoccupied mate. In most webs one will find the oversized female, the puny males and tiny dewdrop spiders. These small silver spiders are kleptoparasites, they patrol the web picking off the smaller prey caught therein and avoiding the owners who will eat the house guest if caught.

The webs of the Golden Orb spiders are extremely strong. The female begins a web by sending out a stand of ultra thin sticky silk into the wind. With luck this strand will stick to an upright branch. Then she will release a much thicker line allowing the wind to slide it across the first. Once the line is thick enough to carry her she will cross to the second post and continue spinning the web. The silk of the orb spiders is exceptionally elastic and can stretch up to 40% before snapping. Generally, spider silk also known as gossamer, has a tensile strength comparable to that of high-grade steel, so strong that a strand with a radius of 3 cm can apparently stop a Boeing 747. For years now research has been ongoing on how to manufacture, among other things, bullet proof vests out of spider silk. The stumbling block appears to be finding sufficient filament to weave the material. Silk is a protein, but unlike other proteins it does not decompose. We preserve other useful proteins by cooking, salting, drying etc. Spider silk has 3 ingredients that prevent its decay. Some of the proteins found in sour milk share a number of these properties. Researchers are now using a strategy called Transgenic animals to explore making synthetic spider silk. Transgenic animals are animals that have had genes from other species inserted into their genetic codes. In this case; miniature goats in New Zealand have had a silk producing gene added to their genome. Somehow the scientists anticipate producing spider silk from the goat milk of these Transgenic animals!

While all this research goes on the orb spiders have a busy time producing the golden silk and maintaining their remarkable webs. The genus name Nephila is appropriately derived from Greek, “nen” meaning “to spin” and “philos” meaning “love”- translated into “fond of spinning”.