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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA
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 Posted: Sat Oct 14, 2006 11:57 pm Post subject: Foot of a jumping spider |
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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! 
--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
Posts: 1944
Location: Croatia
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| Posted: Sun Oct 15, 2006 12:15 am Post subject: |
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Wow! Great.  I think Gecko lizards uses van der Waals forces too.
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Noticing of my "a" and "the" and other grammar
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rjlittlefield
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| Posted: Sun Oct 15, 2006 12:37 am Post subject: |
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| MacroLuv wrote: | | I think Gecko lizards uses van der Waals forces too. |
Yep, that's mentioned in one of the articles I linked.
--Rik |
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DaveW
Joined: 04 Aug 2006
Posts: 1593
Location: Nottingham, UK
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| Posted: Sun Oct 15, 2006 12:40 am Post subject: |
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Got a good set of claws too!
DaveW |
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rjlittlefield
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| Posted: Sun Oct 15, 2006 1:26 am Post subject: |
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| 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
Posts: 6372
Location: Western North Carolina
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| Posted: Sun Oct 15, 2006 4:09 am Post subject: |
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Rik said:
| Quote: | | Very clever, the way these critters are put together! |
...but oh so easy to dismantle them! 
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. 
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Rutherford Co., Western North Carolina
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beetleman
Joined: 04 Aug 2006
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Location: Southern New Hampshire USA
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| Posted: Sun Oct 15, 2006 5:24 am Post subject: |
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Wonderful photo Rik. Very nice detail. I have read about the geckos but did not know the spiders did the same thing (I think your stack is better than the SEM picture in the article  )
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rjlittlefield
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| Posted: Sun Oct 15, 2006 10:41 am Post subject: |
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| beetleman wrote: | | Very nice detail. I have read about the geckos but did not know the spiders did the same thing (I think your stack is better than the SEM picture in the article ) |
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...
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
Joined: 27 Jul 2006
Posts: 6372
Location: Western North Carolina
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| Posted: Sun Oct 15, 2006 11:19 am Post subject: |
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Well we all now know that spiders...don't have "toe cheese." An outstanding follow up image there Rik, cool 
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Ken Ramos
Rutherford Co., Western North Carolina
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Cyclops
Joined: 05 Aug 2006
Posts: 2258
Location: North East of England
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| Posted: Mon Oct 16, 2006 9:33 am Post subject: |
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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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Canon 10D | EOS 300 (Rebel-film) | Panasonic FZ-7 EB | Vivitar/Cosina 100mm f3.5 macro lens | EF 75-300 f4.5-5.6 USM III | EF 50 f1.8 II | Vivitar Series 1 19-35 f3.5-4.5 | Slik 88 Tripod. | My macro shots:
http://stumm47.deviantart.com/gallery/#Macro-and-Close-up |
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Cyclops
Joined: 05 Aug 2006
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Location: North East of England
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rjlittlefield
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| Posted: Mon Oct 16, 2006 11:27 am Post subject: |
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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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Location: Invergordon, Scotland
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Cyclops
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DaveW
Joined: 04 Aug 2006
Posts: 1593
Location: Nottingham, UK
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| Posted: Mon Oct 16, 2006 1:05 pm Post subject: |
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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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