Spider silk starts out in the silk glands as a watery gel of long protein chains, which is funnelled down a gradually tapering tube. As the tube narrows, coatings are applied to the mixture (to provide stickiness and water resistance, for example) before it emerges through tiny spigots (devices that control the flow of liquid) on the spider’s spinnerets.
The gel solidifies only when stretched, so rather than being squeezed out like toothpaste, it is pulled out by a motor-like valve in each spigot.
A battery of silk glands produces a wide array of fibres with different properties used for specific tasks – for instance, a dragline, snare, web support or egg case.
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