Tarantulas shoot silk from feet

Tarantula spider
Tarantula spider. Credit: International Society of Arachnology

Climbing is possibly one of the riskiest things an adult tarantula can do. Weighing in at anything up to 50gm, the dry attachment systems that keep daintier spiders firmly anchored are on the verge of failure in these colossal arachnids. 'The animals are very delicate. They wouldn't survive a fall from any height,' explains Claire Rind from the University of Newcastle, UK. In 2006, Stanislav Gorb and his colleagues published a paper in Nature suggesting that tarantulas may save themselves from falling by releasing silk threads from their feet. However, this was quickly refuted by another group that could find no evidence of the silk. Fascinated by spiders and intrigued by the scientific controversy, Rind decided this was too good a challenge to pass up and discovered that tarantulas shoot silk from their feet when they lose their footing. She publishes her results in The Journal of Experimental Biology.

Teaming up with undergraduate Luke Birkett, Rind tested how well three ground-dwelling Chilean rose tarantulas kept their footing on a vertical surface. Gently placing one of the animals in a very clean aquarium with microscope slides on the floor, the duo cautiously upended the aquarium to see if the could hang on. 'Given that people said tarantulas couldn't stay on a vertical surface, we didn't want to find that they were right,' remembers Rind. But the spider didn't fall, so the duo gave the aquarium a gentle shake. The tarantula slipped slightly, but soon regained its footing. So the spider had held on against the odds, but would Rind find silk on the microscope slides?

Looking at the glass by eye, Rind couldn't see anything, but when she and Birkett looked closely under a microscope, they found minute threads of silk attached to the microscope slide where the spider had stood before slipping.

Next, Rind had to prove that the silk had come from the spiders' feet and not their web-spinning spinnerets. Filming the Chilean rose tarantulas as they were rotated vertically, Rind, Benjamin-James Duncan and Alexander Ranken disregarded any tests where other parts of the spiders' bodies contacted the glass and confirmed that the feet were the source of the silk. Also, the only produced their safety threads when they slipped.

But where on the spiders' feet was the silk coming from? Having collected all of the moulted exoskeletons from her Mexican flame knee tarantula, Fluffy, when she was young, Rind looked at them with a microscope and could see minute threads of silk protruding from microscopic hairs on Fluffy's feet. Next, the team took a closer look at moults from Fluffy, the Chilean rose tarantulas and Indian ornamental tarantulas with scanning electron microscopy and saw minute reinforced silk-producing spigots, which extended beyond the microscopic attachment hairs on the spiders' feet, widely distributed across the foot's surface. Rind also looked at the tarantula family tree, and found that all three species were only distantly related, so probably all tarantula produce the life-saving silk threads.

Finally, having noticed the distribution of the spigots, Rind realised that tarantulas could be the missing link between the first silk-producing and modern web spinners. She explains that the spread of spigots on the tarantula's foot resembled the distribution of the silk spigots on the abdomen of the first silk spinner, the extinct Attercopus spider from 386 million years ago. The modern tarantula's spigots also looked more similar to mechanosensory hairs that are distributed over the spider's entire body, possibly making them an evolutionary intermediate in the development of silk spinning. So, not only has Fluffy settled a heated scientific debate but she also may be a link to the spinners of the past.

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More information: Rind, C., Birkett, C. L., Duncan, B.-J. A. and Ranken, A. J. (2011). Tarantulas cling to smooth vertical surfaces by secreting silk from their feet. J. Exp. Biol. 214, 1874-1879. jeb.biologists.org/content/214/11/1874.abstract
Citation: Tarantulas shoot silk from feet (2011, May 16) retrieved 16 October 2019 from https://phys.org/news/2011-05-tarantulas-silk-feet.html
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May 16, 2011
This article is an excellent demonstration as to why the single ancestor evolutionary theory is a load of sheer speculation.
Firstly, the researcher did excellent work in following up a statement by previous others - doing the specific experiments and observations to determine that the spider does use silk to adhere to a surface to prevent itself from falling. This is real science in the strictest sense of the word - theory followed by repeatable observation.
Then comes the leap of faith - sheer speculation on the part of the same researcher - that this is now the missing link between a 380million year ago spider and modern spinning units. Notice that this cannot be observed, cannot be verified and cannot be repeated. It's simple guess-work of the highest order. It's a story that shows she supports evolution. It will no doubt be repeated as truth in some other report. That's the way it works with evolutionary stories. Note that evolution is ASSUMED 2B true first, then supported after.

May 16, 2011
Notice that this cannot be observed, cannot be verified and cannot be repeated. It's simple guess-work of the highest order. It's a story

Pot. Kettle. Black.

May 16, 2011
Those who hold onto the belief in Naturalism scoff at the Goddidit explanations that theists apply to remarkable examples of equipment in living things. Yet I feel that as we learn more about the layer upon layer of subtlety in living things, the Goddidit explanation becomes more than a simplistic cop out. It is becoming a unavoidable and compelling explanation for a myriad of amazing and wonderful things. While someone can envision a scenario where some rudimentary webslinging may exist a precursor to this or another example of "adaptation", the fully formed intricacy of everything, wherever we look, shouts creator.

May 16, 2011
the Goddidit explanation becomes more than a simplistic cop out.

No, it just becomes more and more of an indication that some people cannot get a handle on some very simple things:

1) The time involved in evolution
2) biology doesn't work like machinery, where you add one thing and leave everything else the same. in biology EVERYTHING is a subject of mutation and evolution - all at the same time.

the fully formed intricacy of everything, wherever we look, shouts creator.

No. It just shouts: Selection pressure.

If it DID shout creator then you have to ask yourself: Why would god create imperfect specimens 386 million years ago and not just have one, perfect, unchanging specimen? Why would He make entire species that die out?

So either He messed up with 99.9+% of his creation (all the species that have died out to date) or - and this is the simpler explanation: we're just seeing evolution at work and He's just a figment of your imagination.

May 16, 2011
holy smokes. cfge has been spamming all morning... how long till you knock out the account?
Oh and to comment on topic I think it's great that she was able to verify the silk thing. It really makes the group that came out and said no initially sound like morons. Another thought; will this change future descriptions or portrayals of Spider-Man?

May 16, 2011
...the fully formed intricacy of everything, wherever we look, shouts creator.

Certainly a "creator", must be far, far more "intricate" than Its creation. Following your line of reasoning, does this then not shout a Creator of the creator? ...and on and on?

May 16, 2011
I like that logic JamesThomas. I've never heard it put quite that way before. It does make the whole creator thing just sound even sillier.

May 16, 2011
I love how the mere mention of a possible evolutionary link brings out the fundies in droves!

I hope that this finding leads to better artificial silk production. From what I can tell, it's the spindles that shape the silk proteins that we are having trouble reproducing. The web proteins themselves are easy and we have goats that can produce them today.

May 16, 2011
So the creator of fluffy and her elders was Lolth... she's the god queen of spiders...

Going by that god theory thing they keep spinning [har har]

/sarcasm 8-)

May 17, 2011
So the article speculates on an evolutionary possibility. Then "kevinrtrs" comments on the transition from the mode of scientific investigation and reporting to that of speculation on evolutionary theory. Fine. Then we get the whole "creation" vs. "evolution" argument, which has by now degenerated into ad hominem attacks, since neither side can "prove" their position. Has anyone observed this kind of behavior before? Perhaps a true scientist among us could establish how bashing each other over unprovable matters has elevated us as a species through natural selection: those who bash best survive best. How and when did science mutate into such a state? Was it the Copernican revolution? Earlier? The arguments for and against both evolution and creation are well publicized and accessible. Would it be possible to simply acknowledge that well meaning people differ on identifying the origins of certain phenomena - I mean without having to make the other guy seem like an idiot or a villain?

May 18, 2011
Perhaps a true scientist among us could establish how bashing each other over unprovable matters has elevated us as a species through natural selection: those who bash best survive best.

I do not believe this question can be answered any more than evolution/goddidit, but I do believe a turning point in the evolution of idea bashing can be traced to the late 1970s, with the dawn of the BBS, where new dominant species of idea basher was naturally selected by the pressures of this new environment.

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