Horizontal FOV 1.5mm
Canon 10D
Leitz objective lg, 20X, 0.2 NA, on 170mm extension
Series of 44 images @ .0005 inch increments
Diffuse tent lighting
Combine ZM, Photoshop
Collected 7/7/07, imaged 7/8/07
Sorocarps of a Dictyostelid – A Cellular Slime Mold
The sphere topped stalks in this image are the sorocarps of a dictyostelid of a species I have not identified. Rik and Ken have made reference to the dictyostelids in a previous post, MYXOMYCETES XIII - Emergence to Spore Release. The subjects in these images are only the second dictyostelids that I have seen in 30 years of myxomycete study. They are not myxos but the second of three forms of eumycetozoans of which myxomycetes are the largest. The other is the protostelids, known only in laboratory cultures.
Unfortunately in the past I have only been left with a field of headless stalks but I got lucky and caught them early enough with their spore bearing tops still attached. I do not want to give the impression that these are harder to find than the myxos. It is something you have to prepare to look for with planning and optical equipment.
These sorocarps are very small and cannot be seen with the naked eye. A 10X loupe is the minimum device to pick them up in the field, but 20X to 30X dissecting microscope is my preferred magnifier in scanning collected materials. I came across these when reviewing some tremellales I recently collected. The best way to find these is to scan the surface of a decaying log but they exist on many other decaying materials as well.
The image does look a bit strange in some spots. This the first image with this lens and I do not believe I had small enough moves. This is my first set of images using the Combine ZM “Do Average and Filter” macro. The starfish like plant in the frame is something I have picked up in air sampling experiments and may have been discussed on this forum in the past. There are also 5 very small tremellales, the red jelly in the image.
Walt
Not knowing the subject, I'm not seeing anything that looks like stacking artifacts. With a 20X NA 0.2 objective, you're on the edge with 0.0005" steps, but offhand I'd expect the biggest risk is to lose occasional detail. Where are the areas that you say "look a bit strange"?
I may have ran across these at times, not knowing just exactly what they were and more than likely ignoring them altogther. I must learn to be more observant. As for that star shaped object, I believe someone ID'ed one of those things over in the microscopy forums but it was in our old galleries, if I am not mistaken. If not in our old galleries, I must have ran across it somewhere else but at the moment I cannot remember what or where it was or what was said about it. 
