Every four years when I watch the swimming olympics, I am reminded how amazing it is for a human to cover 100m in roughly ~50 sec (butterfly stroke). But the world of swimmers (when you include single celled organisms and small-scale swimmers) is far and varied; and sometimes it’s hard to believe your eyes.

In my recent batch of sea-water – which I left to rot for some time – I found a surprisingly fast and dexterous swimmer. This little thing was like a high-speed race car, which could turn, go back and forth and make amazing turns. From the speed, I immediately knew this was some kind of ciliates (single-cell microorganisms covered with many many many cilia – thousands on a single organism). Most flagellates (with long swimming structures, relatively few per single cell) can swim around 300microns or so per second; but when I clocked the ciliate I was watching – it was going almost 1 to 2mm/sec.

Watch the video for the fascinating and complex behavior.. taken with my Foldscope, 140x setting with an iPhone5.

Methods:
1. Because I wanted the swimming micro-organisms in a condition where they could swim; I took a double sided tape and mounted it on two sides of a glass slide. I covered this area with a drop of water (which possibly carried many micro-organisms) and covered the top with a cover slip. I did not seal this slide; but often I add nail polish on the side to seal it completely not to have any leaks.
2. You can also make an easy wet mount (a slide with water in the same) by just using two sides of tape provided with the foldscope kit. This allows you to trap a drop of water in between the slides, and thus easily create wet mounts without using any sealing (nail polish).
3. That’s it – after observing these ciliates for some time; I decided to collect some data on my iPhone5. I was up for a big surprise..watch the movie above.
4. In some sections, I compared the distance covered by the body length of the ciliate itself. I use an open source program called “imageJ” – which is pretty much the best program to analyze video microscopy data. You can download and install the same here: ImageJ – another similar program is called “Fiji which stands for “fiji is just imagej” – very useful for analysis.
5. In the very end of the video – I wanted to see a rough trajectory that the ciliates took. Thus I use the “z projection->maximum intensity” feature in imageJ to “add” all the images of the movie – to make a trajectory map. This allows me to see the behavior in a single image.

Observations and thoughts:
1. I am amazed how fast these things were swimming. The video is real-time!!!! And you can clearly see the ciliate cross the entire field of view (nearly a mm or more) in less than a second. I tracked the organism more carefully, and I can see it was traveling at nearly ~25 body lengths per second!!! Just think about that.. Michael Phelps fast swimming records of 100m in 50 seconds in butterfly stroke – only implies one body length per second. Although the laws of physics are quiet different at small scales (what constitutes resistance and how you generate thrust is very different for small scale and large swimmers); to see a speed of 25 body lengths per second is so impressive.
2. To me what is even more amazing are the patterns of behavior seen in the swimmer. It turns, it stops, it back tracks – as if trying to sense something and making decisions at milli-second speeds (the transition from one mode, say going forward to going backward is less than 100ms); what molecular machinery allows for such fast decision making processes? What circuits exist that allow a single cell to make such complex behaviors?
3. I also noted a lot of other smaller organisms are moving and swimming around (although at slower speeds). What is also clear in a few frames is one micro-organism is actually pulling and towing a “brown algae” with it. Let’s see if you can find out where that is in the video.

So, go ahead and get some pond water and film these fast swimmers. Let’s see if you can beat my record of 25 body lengths/second.

Next, I will post some videos of beating cilia I collected with my Foldscope; to get to understand how can something so small swim so fast!!!

cheers
manu