For talking about migration, here’s a short video showing one day’s worth of air traffic around the world from the Zurich School of Applied Sciences. It’s pretty amazing.
Depth of Field Demonstration: On a Simulated Microscope
At higher magnifications, microscope lenses will only be able to focus on layers within your specimen. You could take a series of images with different focal planes and stack them together, but without a camera mounted on the microscope, getting images to line up right for focus stacking is quite the challenge. The alternative is focusing in and out until you get a feeling for the three dimensional shape of the specimen.
Since I don’t have a camera mount I’ve created an html5/javascript page that simulates focusing in and out of a sample. It’s embedded above, but a direct link is here.
You can use the knobs to the right of the image to adjust the focal plane. You should be able to see hairs on the top and bottom of the transparent wing.
Insect Appendages: Practicing Mounting Specimens
I’m really beginning to like the idea of giving students the option of putting together their own, individual, slide collections. So, to practice mounting slides with nail polish, I tried to make a start on my own permanent slide collection. It was partially successful.
Procedure
To start, I found a dead fly near the window. It had been dead for a while and so I assumed it was pretty well dried. Carefully, under the stereoscope, I pulled off the appendages — antenna, wings, legs — for mounting. The fly itself was too big to mount, as were the major body parts, but as I was dismembering it the head, thorax, and abdomen came apart. In fact, the head broke into a few pieces as well, including one of the compound eyes, which I thought would be worth trying to mount even though it was somewhat thicker than the other parts.
I started with the antenna. The procedure I tried to follow is simple. Place a small drop of nail polish on the slide and then put the sample on the nail polish drop. Next place a drop of nail polish on the coverslip, flip it upside down and put the two drops together. The weight of the coverslip will flatten nail polish out into a thin layer. You then put small drops of nail polish at each corner of the coverslip. The polish will seep in between the slide an coverslip by capillary action until the entire underside of the slip is saturated.
Since the antenna was so small, I actually broke a cover slip into quarters to make them, I hoped, easier to manage. The slides were then left to dry overnight.
The initial results were, as I have mentioned, mixed. Bubbles encroached on a number of the specimens, particularly the thicker ones, like the rear legs, but for the most part, the specimens were clearly visible, with a minimum of obstructions to the view.
Antenna
Antenna at 40x magnification:
Antenna at 100x magnification:
Antenna tip at 400x:
Legs
Of the four leg slides I made, three had serious problems with bubbles, and the one that did not was missing the end segment of the leg. Part of the problem with the bubbles may have been that it took me a while to get the legs onto the nail polish drops, which allowed the drops time to evaporate. This could have resulted in a more viscous drop by the time I added the coverslips, which would not have lain down quite as flat, leaving space for the bubbles to come in. Another possibility is that the thickness of the legs made the glass coverslip tip up toward one side.
Fly front leg:
Middle leg:
The tip of the middle leg is inside the nail polish.
Rear leg:
Rear Wing
The last appendages I mounted were the two small, rear wings. They were very thin and I placed them both under the same full sized slide. It worked quite well.
Rear wing at 40x:
Rear wing at 100x:
Rear wing at 400x (focus stacked):
Fly Eye
The eye came out remarkably well.
Pond Microbe Identification
Mic-UK has an excellent reference for microscopic life. It’s where I learned about Gastrotrichs.
Making Slides: Mounting in Nail Polish
Now that I have a few new microscopes, I’d like students to be able to make their own, permanent, slide collections. Walter Dioni has some superbly detailed pages on how to mount samples for microscopy. I could not find a good, up-front, index, so for the record, here are his pages on mounting slides:
- Intro. to mounting with liquid media
- Solid media: Sucrose, glucose, fructose (Karo syrup) mounts
- More complex mixed mounting media (here and here)
- Gum arabic media
- Glycerin Jellies Mounting
- Nail Polish mount
Most of these methods use chemicals that are safe to work with (all are non-toxic), but using nail polish appears to be the easiest — it’s a mount and a sealant in one — so that’s the one I tried first, using a bottle of Strengthener, Nail Hardener. The Karo syrup, and glycerin methods also seem reasonably easy, and it may preserve some of the organic colors better so I may try those later when I have the time.
P.S.: Dioni also has a good page on pollen microscopy.
Your Fonts can Affect Your Grades
Inside Chris Gayomali’s interesting article on, “How typeface influences the way we read and think” is a bit about an undergraduate student who found that the font he used affected the grades he got on his papers. Turns out that some fonts, Georgia for example, are better than others.
P.S. As the article points out: don’t use Comic Sans.
Ticks in the Woods
While walking through the woods to recover the skeleton the other day, I picked up, or rather was boarded by, a few ticks. So when I got back to school I plopped them under the stereoscopes to try to identify them.
They were both lone star ticks (Amblyomma americanum): one adult and one juvenile.
Under the microscope, they were quite pretty with their very interesting red and black patterns.
Note:
Purdue’s extension service has an excellent reference page on basic tick anatomy and ecology for a lay audience, and Colonial Pest Control has a very readable overview of The Biology of Ticks (↬ Jay O.) that goes into their life cycles and how to deal with them.
Much greater detail can be found in the Tick Gross Anatomy Ontology, but the best reference I’ve found so far is the USDA’s Handbook (485): Ticks of Veterinary Importance (pdf). There you can find great anatomy diagrams and interesting biological and ecological information. One curious piece of information is that ticks can survive a long time (three years in one case) without a blood meal. It also includes some excellent diagrams:
A Skeleton in the Woods
Just out of the blue, I got a text from Maggie (Eisneberger) yesterday saying, “Wanna see something awesome. Bring the kids.” Well I didn’t have the kids with me, but I went over anyway. She and her niece had found an almost complete skeleton in the woods.
Since I’ll be teaching biology next year, I’ve been on the lookout for a good skeleton. The last time I had one was when my middle school class found a raccoon skeleton on an immersion trip. They brought it back to school, cleaned it up, and reassembled it on a poster board. It was an awesome learning experience.
This skeleton is even more complete. Even some of the cartilage between the vertebrae was dried out and preserved. It was a bit puzzling that the whole skeleton seemed to be there, and had not been too disturbed by scavengers even though, based on the state of decay, it had been there for quite a while.
We collected as much as we could, although some of the smaller bones in the hands and feet are quite tiny.
Maggie lent me her book on the animals of Missouri so I could try to identify it based on the teeth. However, later yesterday evening I got an email from her. She’d been talking to her brother, who’d, back in March, shot a raccoon that was going after his chickens. He’d left the body out in the woods.
Well now someone/s will have a nice little project in the fall.