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What Makes Darwin’s Bark Spider Web So Amazing?
Spider’s web has always fascinated us, whether in the corner of your closet or room. But what if you noticed a web hoisted stretching across a river, waiting to trap its prey?Since their discovery in 2010, Darwin’s Bark Spiders, Caerostris darwini, have been showstoppers for their web-spinning skills.
This tiny architect, a resident of the lush rainforests of Madagascar, spins 2D orb webs, which are one of the toughest natural biomaterials.
The web of wonders
The web cast by Darwin Bark spider shimmers over the water body like a fishing net and is considered the largest web of any species of spider, spanning about 25 meters.
The spider fiber’s remarkable strength is due to its unique extensibility, allowing it to stretch significantly more than other silks before breaking— thus enabling it to trap from tiny insects to small birds. These features earned its position in Guinness World Records as the strongest spider web.
The secret behind these megastructures is the spider silk, which is twice as tensile as any other spider silk and, unbelievably, about ten times tougher than Kevlar!
Two factors contribute to the remarkable toughness of the web:
(i) the quality of the spider silk and (ii) the web architecture, which helps the spider to prey on insects and small birds.
What makes Darwin's bark spider web so tough?
The dragline web of Darwin’s Bark Spider’s silk overpowers at 354MJ/m3 compared to other orb webs by Nephila pilipes, which carries a toughness of 100MJ/m3.
Spiders can have seven different types of silk glands that contribute to the quality of silk. The Darwin bark spider spins a dragline web made of spider silk protein, spidorin released by major ampullate (MA) glands. In addition to MaSp1 and MaSp2, the Darwin bark spider expresses another spidroin, MaSp4, with a unique amino acid motif, GPGPQ, which contributes to the silk’s extensibility and toughness.
The web architecture involves a dragline, radial line, frame line, spiral line, and the center called the hub. In this network, sticky material are secreted at equal intervals on the spiral line to trap the prey.
Sexual dimorphism
The Darwin bark spider exhibits sexual dimorphism, where genders of the same species exhibit different morphological features. Here, females are mammoth, weighing almost 14 times more than the males, imitating Goliath and David. The females are black in color and gigantic, with a body length of 18mm, and the males are red midgets of 6mm.
Unique feeding habits of Darwin bark spider
Predators: The web gigantism traps insects and birds to feed on them. Reports suggest the identification of about 32 mayflies trapped in the orb web.
Cannibalism: Female spiders predate male spiders, which provides nutrients to the females for making baby spiders.
Kleptoparasitism: The spider lets some flies feed on its prey before the spider wraps and devours them.
Biomaterials inspired by nature
There is extensive ongoing research for the synthetic production of spidroins, biomimicking the structure and properties of spider silks. In addition, scientists are exploring the production of different morphologies of nanofibrils, capsules, and hydrogels using spidroins. Spidroins’ tensility, biocompatibility, and biodegradability make them the leading biomimetic for drug delivery and other biomedical applications.
Conclusion
Darwin’s Bark Spider is not just another member of the arachnid family. It’s a marvel of natural engineering, an environmental indicator, and a beacon of biological inspiration.
Glossary
Arachnids: A group of joint-legged invertebrate animals that includes spiders, scorpions, ticks, and mites.
Ecosystem: A biological community of interacting organisms and their physical environment.
Kevlar: A strong, synthetic material used in various products, including bulletproof vests.
Silk: A fine, strong, soft, and shiny fiber produced by spiders and some insect larvae, used by spiders for building webs.
References
Matjaž Kuntner, Ingi Agnarsson “Web gigantism in Darwin’s bark spider, a new species from Madagascar (Araneidae: Caerostris),” The Journal of Arachnology, 38(2), 346-356,
https://www.uml.edu/news/news-articles/2019/abc-super-tough-spider-silk.aspx
Garb, J.E., Haney, R.A., Schwager, E.E. et al. The transcriptome of Darwin’s bark spider silk glands predicts proteins contributing to dragline silk toughness. Commun Biol 2, 275 (2019).
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