Leitz Ortholux microscope
4X Leitz projection eyepiece plus 1/3x relay lens
For all images, taken at different times, and of different feet, a live subject is actively employing van der Walls forces, suspended from a glass “ceiling”.
Image 1- Leitz Phaco 40X NPL objective, 25 images at .5 micron increments.
Entire underside of claw tuff. Width of field = 0.27 mm. B & W employed to reduce affects of chromatic aberration.
Image 2- Crop of image one. Width of field = 0.167mm. At the middle right, complete unobscured seta components are seen with measured widths of 10 microns, length 20 microns. Look on their surfaces and any other to see the small dots and edge hairs. Are these the microtrichia or fine cuticular hairs or clumps or groupings of them?
Image 3- Zeiss 25X Plan, Ach. 53 images at 1 micron increments. Underside of claw tuff with portion of tarsal leg segment.
Image 4- Olympus S Plan 10X, 97 images at 2 micron increments. Front foot showing tarsal claws retracted to allow claw tuff hairs to engage the glass surface.
Image 5- Olympus S Plan 10X, 66 images at 2 micron increments. Two center feet still engaged to the glass but on their extreme tips. Seconds later they were removed and redeployed.
Image 6- Leitz 4X Plan Fluorite, 36 images at .005" increments. Portion of metatarsal leg segment, full tarsal segment and claw tuff.
Diffused Fiber Optic illumination
Canon 50D
Zerene PMax and Photoshop processing.
Something special and unique for installment Number 50!
These images, taken while the spider, Clubiona canadensis, was hanging upside down, show all the contact surfaces of the claw tuff. Employing the van der Waals forces, created by the fine cuticular hairs making up the surface of the individual seta, the spider keeps from falling to the floor. Image number 1 shows the entire sole of the foot. It is roughly separated down the center into two equal halves. In the cropped image No. 2 each individual, 100 or so, oval shaped objects is called a seta which in turn have hundreds of yet even smaller microtrichia or fine cuticular hairs on their surfaces.
In reality the actual tips of the fine cuticular hairs are what is in contact with the glass, but my microscope cannot resolve them. A scanning electron microscope (SEM) employing magnifications between 3000X and 10,000X is required. It reveals a disk like feature it the tip of every hair.
It is most curious how the limited resolution of my microscope, at this magnification, shows them as rows of dots and hairs at the edges. This may have something to with the fact that they are actively employing the van der Waals forces. SEM images with much more resolution, show the cuticular hairs laying randomly. However those images were not of a claw tuff engaging a surface. The question I pose in the Image 2 caption is what am I seeing here? Clumps of these microtrichia or what? I should not be able to resolve the individual microtrichia.
These images proved to be very difficult due to the fact that the van der Waal forces do not seem strong enough or stable enough to maintain the spider in place for very long. During the few successful exposures it was maintaining itself, but it soon began to slip. Under magnification (100 to 250X) you can see the foot sliding towards the center of the body almost constantly. This would result in an eventual repositioning of all eight legs. The spider will maintain contact until at least some of the feet are on their tip-toes or the extreme ventral points, as seen in image 5.
The best known “ceiling” walking spiders are the jumpers or the Salticidae. Rik Littlefield produced, sometime back, a superb image of that spiders claw tuffs from the side. Apparently several of the hunting spiders posses this ability and Clubiona canadensis is, in my mind, one of the best. Hope to get a Salticidae to be as cooperative in the future.
Enjoy Walt
