Natures wonders: spider silk 10X stronger than Kevlar (Introduction)

by David Turell , Friday, July 26, 2019, 01:12 (1946 days ago) @ David Turell

The spider spins huge webs over rivers in Madagascar:

https://cosmosmagazine.com/biology/madagascar-spider-silk-10-times-stronger-than-kevlar...

"Darwin’s bark spider (Caerostris darwini), native to Madagascar, produces the largest orb-shaped webs in the world, with diameters up to 2.8 metres.

"The species exploits insect prey that fly above rivers, positioning webs midway between the banks, suspended from silk “bridge-lines” that can be as long as 25 metres. (my bold)

Gram for gram, spider silk is an extremely tough and flexible material,

***

"Darwin’s bark spider, however, takes tensile strength an entirely new level. Its dragline silk – the type that forms the energy-absorbing primary spokes of the orb-web – is twice as strong as that of any other silk thus far tested, and an astonishing 10 times stronger than Kevlar.

"... scientists led by Jessica Garb from the University of Massachusetts Lowell in the US might have found the answer. In a paper published in the journal Communications Biology, they report that the silk is the result of “a suite of novel traits from the level of genes to spinning physiology to silk biomechanics”.

"When Garb and colleagues analysed the structure of bark spider dragline silk they made an unexpected discovery. All orb spiders produce silk containing two distinct sets of repetitive proteins, called spindroins, known as MaSp1 and MaSp2. The number of repeats, and the ratio between the two types, govern the properties of the various types of silk each spider produces.

"The dragline silk of Darwin’s bark spider, however, contains a third spindroin, which the researchers dubbed MaSp4a. This protein set lacks some of the components of the other two, but is unusually rich in a type of amino acid called proline, which is associated with elasticity.

"This, the researchers suggest, “may in part explain the greater extensibility and toughness” of the fibre.

"Dragline silk is produced in all spiders from glands known as major ampullae. The researchers found that these glands in the Darwin’s bark spider are “unusually long” – an evolutionary adaptation, they suggest, that may influence the structure and tensile strength of the silk, although exactly how, they add, “remains an important open question'”.

Comment: It is impossible to imagine this silk developed by trail and error. Note my bold to see the size of the construction these spiders had to learn how to do across small rivers. Only design fits.