David Beeson, March 2022
I’m about to sell my microscope, as a new one is on its way to me. So, I thought I would give the old one an outing – a sample of pond water. Oh, what wonders! If you have access to a microscope and have never looked at pond water do it.
The first thing you’ll spot, once the microscope slide has its drop of water and a coverslip has been added, will be big circular organisms. Clear in the middle with a distinct dark line around the edge. What can it be? Answer: an air bubble, because you, in haste, didn’t lower the slip one side first, but just dumped it down directly. Woops. Then you find the image is unclear, so you start again and clean the eye and objective lenses with lens tissue or optical glasses cloth. Double woops.
So, with the substage condenser as high up as it will go, then down half a turn, you adjust the iris diaphragm to be as small as possible (gives more detail, as in a camera) but with enough light reaching the slide.
Always start with the least powerful objective lens and carefully lower it until it is close to the slide and coverslip, and adjust the slide to the best position. Now, at last, you are allowed to look through the eye lens and slowly move the focus to raise the objective lens to focus. Wonderful things become visible, especially after you employed the fine focus. Minute creatures dart across your field of view, others twirl and gyrate. Yet more you spot attached to debris.
Now, using the fine focus move it slightly up and down to spot the three-dimensional aspects of the miracle before your eyes, before moving the slide to seek out the best possible location of the ‘soap opera’ before you.
I spent most of the time using a x10 eye lens and x10 objective – low power, x100 total magnification. High power is x10 x40, or x400 total magnification. But, if you have a x4 objective that can be useful for larger objects such as aquatic leaves. It is possible that your machine has an ‘oil emersion lens’ – don’t use it unless you’ve been trained in microscopy, as you need to use a special oil between the lens and slide and it can get very messy.
What did I spot? Lots of single-celled round algae, the base of the food chain. The twirlers are euglenoids, cute algae that think they are animals in that they can both photosynthesize and engulf minute food, all the while hurtling around using a spiral flagellum. Wonderful!
Then I mounted some weed on a slide and studied it. The individual cells were clear and lots of filamentous algal strands were attached. Here the cell wall and cell contents with its green pigments came clear. Later in the year I can be voyeuristic as algal sex occurs before my very eyes with conjugation tubes and moving cytoplasm beating any human ‘blue movie’. Perhaps!
And, what is that? Ah, vorticella. It’s a stalked single-celled animal (protozoan) with a fringe of minute cilia beating to draw in aquatic bacteria to its gut-like structure.
Now do I go for bigger things? Like, capture a tadpole in a small dish, with minuscule amounts of water, so I can look at its tail and see the blood capillaries and even the red blood cells passing through it? No, I’ll save that for another day.
Does anyone want to buy my microscope before it goes on eBay?
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