MicrobeHunter.com Microscopy Forum

Thank you to linuxusr for initiating this subforum. As mentioned in that thread, a couple of my classmates and I did a small undergraduate project years ago on the relationship between morphological symmetry and swimming speed of various unicellular phytoflagellates.

We obtained monospecific cultures of 13 marine flagellate species and quantified their body symmetry and surface area:volume ratio using geometric formulae. We shot videomicrographs of them swimming, and used a computer programme (written from scratch in IDL by my collaborator) to track the microbe as it moved through the water and measure its speed.


Gambierdiscus cf. belizeanus, photographed using a Zeiss inverted laser scanning confocal microscope with fluorescence.

We used cavity slides that we constructed ourselves, by sticking an acrylic slide with a hole in it to a normal glass microscope slide using UV-cured Norland Optical Adhesive (I still have the slides after 20 years!). Here's one of them:




Calibrating the videomicroscope.

Alas, we didn't find any really compelling pattern statistically, but it was fun and we marveled at the intricate geometries of the flagellates - especially the dinoflagellates which had armour plating that looked like some kind of Lord of the Rings/Star Wars thing and their curious helical central groove and swimming motion which probably makes it more efficient, "screwing" through the water which to them at that spatial scale is as viscous as treacle.

We also learnt that there were at least two types of flagellar propulsion - linear propulsion by the flagellum/flagella sticking out the back, and helical propulsion by the transverse flagellum (if present).

Unfortunately we didn't have time to look at ciliates.

Anyone interested in more of the methods, calculations and behavioural ecology discussion can see the full report here, including the source code of the programme for speed measurement.

Great project … Thanks for the link

MichaelG.

My pleasure, I hope someone will find it useful for their studies or have interesting observations and findings to add.

I dug up some old printouts showing snapshots of the video feed and the computer doing the tracking:







Unfortunately in the excitement of the moment we did not think of taking a photo of the microscope. It wasn't a very fancy one but it had the necessary fittings and was calibrated to research-grade accuracy. I just re-read the report and I wrote that we used an "Olympus BH2-UMA bright-field microscope" (whatever that means - it was probably a BH2 and I read the model name on the vertical illuminator and thought that was the name of the microscope) and "Hamamatsu C2847 video camera attached to the microscope through an MTV-3 fixture and fed into a Toshiba V-E27 recorder".

I read a thesis by a woman who tracked the movements of ants like this. I wonder what they would conclude from this.

I don’t think ant body shape would influence speed as much as plankton shape influences speed (and style of swimming which may affect efficiency and predator evasion), if that’s what the woman did. The water is much more viscous to the plankton than the air is to the ant. Or did the woman put the ants in water?! Even then the Reynolds number would be much lower for a flagellate than for the ant.

Ant movement is really interesting in other ways, as they have social self-organization and more linear trails over longer distances etc., so the underlying mechanisms are different from plankton.

But both ants and plankton may have similarities in terms of random movement and diffusion components, which may allow them to explore a larger area with more chances of finding new sources of food.

What were her conclusions?

She concluded that ants move essentially randomly. They suçeed because useful material and food was well distributed and accessible in their environment.

Such an interesting experience! Thanks for sharing.

Hopefully forum member Einman will chime in about ants.