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Foot of a jumping spider
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rjlittlefield
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PostPosted: Sat Oct 14, 2006 11:57 pm    Post subject: Foot of a jumping spider Reply with quote



The feet of a jumping spider are covered with lots and lots of hairs, organized as numerous larger hairs each tipped with a tuft of much finer hairs called "setules". The setules are attracted to solid surfaces by very short-range van der Waals forces that can be broken and re-established an indefinite number of times without weakening. Individually, the attractive forces are tiny, but summed over the huge number of them, the aggregate force can be 170 times the weight of the spider! At least, that's what these articles say: "Spiders make best ever Post-it notes" and "Spiders get a grip".

An optical image like I've posted here doesn't have enough resolution to show the individual setules, but I believe the tufts of them can be seen as fuzzy gray blobs at the ends of the black hairs.

Another interesting feature visible in this image is some "beading" visible on many of the long sensory hairs. At first I thought this might be an artifact of the stacking procedure. But the beading is present even in individual frames, so I think it's real. What is its significance, I have no idea.

It's the usual situation -- get close, get questions. Extreme close-ups are seldom boring! Very Happy

--Rik
Canon 300D, 10X NA 0.25 achromat on 180mm extension, stacked by Helicon Focus at 0.00025 inch. Cropped to about one half frame width, shown here at about 200X.
The web page linked above references an article published 19 April 2004 in the Institute of Physics journal Smart Materials and Structures).
More info and additional pictures can be found by visiting http://www.iop.org/ and searching for "setules".
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MacroLuv



Joined: 28 Aug 2006
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PostPosted: Sun Oct 15, 2006 12:15 am    Post subject: Reply with quote

Wow! Great. Shocked I think Gecko lizards uses van der Waals forces too. Very Happy
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Noticing of my "a" and "the" and other grammar
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rjlittlefield
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PostPosted: Sun Oct 15, 2006 12:37 am    Post subject: Reply with quote

MacroLuv wrote:
I think Gecko lizards uses van der Waals forces too. Very Happy

Yep, that's mentioned in one of the articles I linked.

--Rik
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DaveW



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PostPosted: Sun Oct 15, 2006 12:40 am    Post subject: Reply with quote

Got a good set of claws too!

DaveW
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rjlittlefield
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PostPosted: Sun Oct 15, 2006 1:26 am    Post subject: Reply with quote

DaveW wrote:
Got a good set of claws too!

Indeed, and I notice they're kind of retractable. Depending on position of the leg and I don't know what else, the claws can extend way beyond the pad of hairs as shown above, or hide completely behind it.

Come to think of it, I guess that makes a lot of sense. Sometimes the spider needs to use the hairs for adhesion to some surface, and it would not be good if many of the hairs were held away from the surface by the claws. But when the claws are needed, they'll work a lot better if they stick out beyond those really pretty stiff hairs. Very clever, the way these critters are put together!

--Rik
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Ken Ramos



Joined: 27 Jul 2006
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PostPosted: Sun Oct 15, 2006 4:09 am    Post subject: Reply with quote

Rik said:
Quote:
Very clever, the way these critters are put together!


...but oh so easy to dismantle them! Twisted Evil

Quite an interesting post here Rik. It is fascinating though how they are constructed. Excellent photograph even though you could not resolve those van der Waals forces very well and I don't imagine I will be using them as post-it notes anytime soon. I wonder who names these anatomical parts anyway. Think
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beetleman



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PostPosted: Sun Oct 15, 2006 5:24 am    Post subject: Reply with quote

Wonderful photo Rik. Very nice detail. I have read about the geckos but did not know the spiders did the same thing Shocked (I think your stack is better than the SEM picture in the article Wink )
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rjlittlefield
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PostPosted: Sun Oct 15, 2006 10:41 am    Post subject: Reply with quote

beetleman wrote:
Very nice detail. I have read about the geckos but did not know the spiders did the same thing Shocked (I think your stack is better than the SEM picture in the article Wink )

Well, of course I just couldn't resist trying to get even closer.

Canon 300D, 20X NA 0.40 achromat on 150mm extension, cropped and resized to 80% of "actual pixels". Stacked at 0.0002 inch.


I'd be a bit surprised if this is resolving individual setules, which are described as "just hundreds of nanometres in width". Maybe they clump together -- I know that this beast had its feet wet and did not get a chance to clean them before posing. Or maybe this kind of spider has bigger setules. An SEM could tell us... Wink

But at least now we can see that those blobby ends are actually spatulate and that the gray stuff has some interesting texture.

We can also see that a bunch of the larger hairs are feathered. I'm not sure whether this explains the "beading" that I mentioned earlier, or whether that's a different structure.

Unfortunately this lens has a pretty small central area where the resolution is really good, so I'd have to pan a bit to put some of the beaded-looking things "front and center", and shoot another stack. Perhaps another time -- I have other things to do today.

Doug, thanks for the kind words about these high resolution stacks versus SEM. I have a zoologist friend who assures me that there are definitely situations where the stacks give more information, for example about colors and transparency. It'll be interesting to see how the biology community incorporates this technology now that it's (relatively) cheap and easy to do.

--Rik
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Ken Ramos



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PostPosted: Sun Oct 15, 2006 11:19 am    Post subject: Reply with quote

Well we all now know that spiders...don't have "toe cheese." Shocked An outstanding follow up image there Rik, cool Cool
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Cyclops



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PostPosted: Mon Oct 16, 2006 9:33 am    Post subject: Reply with quote

Fantastic shot! I tried to get a similar shot of one of my Tarantula's foot but I couldnt get near enough DOF.
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Cyclops



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PostPosted: Mon Oct 16, 2006 9:48 am    Post subject: some SEM images of setules Reply with quote

Rik, I did some googling and found some SEM images of these setules (I'm more familiar with the name setae, are these the smaller scale structures?)

http://images.google.co.uk/images?sourceid=navclient&ie=UTF-8&rls=GGLG,GGLG:2006-23,GGLG:en&q=setules

a SEM imnage of setae:
http://www.lclark.edu/~autumn/climbing/setae.html
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rjlittlefield
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PostPosted: Mon Oct 16, 2006 11:27 am    Post subject: Reply with quote

Cyclops, I'm not sure about the terminology. Based on what I think the sizes are, the "setae" of the gecko are like what I'm calling "hairs" (the black things that are about 100 microns long and have the fuzzy gray spatulate tips). If that's right, then the "setules" of the jumping spider would be equivalent to the "spatulae" of the gecko. See http://www.lclark.edu/~autumn/climbing/seta.html, showing "2 million setae per gecko" and "100-1000 spatulae per seta". Perhaps this is spelled out in the full articles, which I have not tried to track down yet.

The term "setae" (singular "seta") seems to mean different things in different contexts. When I Google "define: setae", I see consistency at the level of "hair", but not much below that. I've always gotten the impression that a seta is anything that looks like a bristle but is smaller than whatever we'd call a bristle on the organism in question.

Thanks for posting a link to those SEM pictures. If you can figure out how to see them at full size, I'd be grateful. Every time I try, I just get beamed back to http://www.iop.org/ , and when I try to work my way down from there, all I can find are the text articles and small versions of the pictures.

--Rik

PS. Excellent gecko pictures, complete with scale bars, can be found here. That url is linked a couple levels down from http://www.lclark.edu/~autumn/, following "Adhesive force of a single gecko seta".
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georgedingwall



Joined: 01 Aug 2006
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PostPosted: Mon Oct 16, 2006 11:47 am    Post subject: Reply with quote

Hi Rik,

Great images and a fascinating subject.

I found this link to a page about jumping spiders feet. It has a couple of SEM images on the page.

http://whyfiles.org/shorties/152sticky_spider/

Bye for now.
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Cyclops



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PostPosted: Mon Oct 16, 2006 11:49 am    Post subject: Reply with quote

I see what you mean Rik, very strange!
The first few pics are all from the same site (http://www.iop.org/ )

but others are located elsewhere and i managed to find a few:

http://www.technovelgy.com/graphics/content/spider-glue-setules.jpg

http://www.technovelgy.com/graphics/content/spider-glue.jpg


"At large magnifications it can be seen that single hairs (setae) are densely covered with numerous setules (image credit: Smart Mater. Struct. 13 512)":
http://nanotechweb.org/objects/news/3/4/13/Kesel.jpg
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DaveW



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PostPosted: Mon Oct 16, 2006 1:05 pm    Post subject: Reply with quote

I am only familiar with the term setose as used in botany. Zoology and other disciplines may use it differently. Here's what our "bible" - "Botanical Latin" by William T. Stearn says:-

Seta. bristle, bristle-like organ, as the fruit stalk of a moss.

Setaceous, Setiformis. setaceous, bristle-like.

Setifer. bristle bearing.

Setose. setose, bristly, i.e. beset with scattered ascending stiff hairs.

Setulosus. minutely setose.

DaveW
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