Images of Pond-life from Video

by Mike Samworth

After reading about other people's exploits with video and the microscope I couldn't resist having a play myself. Though I don't have a video or camcorder of my own I am fortunate in having access to a video camera without lens at work. I have borrowed this on a few occasions and attached it to my microscope. Each time I have learnt a little more about what works best. The following still images are from those first sessions.

Amoeba
These two images are both of good old Amoeba proteus. The first is from early in the video sequence when the organism is still suffering the consequences of being thrown onto a slide. the second shows the creature putting out pseudopodia as it moves.

Another shot of Amoeba, this time under higher magnification and using phase contrast.The latter shows up the highly granular nature of the cytoplasm. The video seems to cope well with phase images. I have found however, that most times using the video, all automatic circuitry should be turned off, especially that for colour balance. Not that much colour balance is needed for Amoeba! I have only had phase contrast available on my microscope relatively recently. As in many things in life, once you have something you wonder how you ever survived without it. Phase contrast is no exception and is especially useful for protozoa.

Paramecium
These two images are both of the ciliate Paramecium. They both show the organism rather flattened. This is due to the presence of silk fibres in the water on the slide. I find that this slows down the movement of ciliates quite well. Just tease out fibres from a piece of silk with tweezers under a stereo mic' and put onto the slide. The image on the right illustrates a common error with video, that of having your lamp turned down. At first you do this because of the high sensitivity of the camera, but of course it adds a colour cast. It is better to turn the auto-circuitry off and adjust manually. Turn your lamp up and use neutral density filters if necessary.

Euplotes
These are two very different views of a very different type of ciliate from the last one. They are both views of Euplotes, a common and widespread hypotrich ciliate. Hypotrichs have 'blocks' of cilia in groups or rows called cirri. They often use these cirri to 'walk' over the substrate. On left is a ventral view, the one normally seen when the organism is free-swimming. On the left is the view from the side of the ciliate.
It effectively illustrates how the ventral cirri that characterise hypotrichs are used for movement over a substrate. This is one of the advantages of video, you can take a sequence and then select out the images that show particular behaviour.

Rotifers
One problem with video is that often the magnification is just too high. So for larger multicellular organisms such as rotifers they more than fill the screen.

This can be avoided in two ways. Either you can use a very low power objective, say 2.5x, or set up your camera at such a position that you can dispense with the eyepiece altogether. This is not optically a good idea but nevertheless has been employed here for these two views of the rotifer Philodina. Of course in professional video systems a supplementary lens would be used instead of an eyepiece to compensate. The rotifer on the left is shown under phase contrast.

Please do not hesitate to contact me if you have any comments or questions - Comments to the author sent via our contacts page quoting page url plus : ('msamworth','')">Mike Samworth.

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