Paramecia self defense

About the shape and function of different specimens
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Martin Parnham
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Joined: Thu Oct 06, 2022 2:43 pm

Paramecia self defense

#1 Post by Martin Parnham » Tue Jan 17, 2023 5:33 pm

Hi Folks - My in-house (literally!) Paramecium jar is thriving so I thought I would try some classic experiments / observations on them.

Paramecia like many Ciliates have organelles called Trichocysts. The filamentous ones found in Paramecia are thought to be used largely for self defense mostly against other predatory Ciliates. When stimulated they discharge tipped filaments. Certain chemicals / toxins can also stimulate their release. This video shows such an event. For the first 20 seconds the paramecium is swimming in its normal fashion. I then introduce concentrated white vinegar and this triggers over the next few seconds filament release from the Trichocysts.
The deployment speed and filament density is impressive. This acts as a deterrent and reduces the predation rate.

Here is a more detailed method for those interested in trying this demonstration.

1) Place a small drop of 3% Methyl-cellulose onto a slide. Then place a similar sized drop of sample water next to it and mix, I use a mounted needle. The Cellulose is non toxic and serves to slow them down to enable observation.
2) Place coverslip onto slide. It is best to only have enough mixture such that there is a an air gap around at least some of the perimeter of the slip. This allows the rapid introduction of the 'toxin'. Capillary action draws it very quickly under the slip and into contact with the sample mixture.
3)Find a suitable specimen for observation, I get it set up and in focus on the x40 objective. Then place a drop of 'toxin' in contact with the air gap under the cover slip. It will be drawn in almost instantly and the Paramecium should respond quickly.

I am sure other chemicals will produce a similar effect.
Be careful to avoid contact between your objective and whatever chemical you are using!
It can take a bit of time / practice to get satisfactory results!

There is plenty of further information on trichocysts on the net for example -

https://pubmed.ncbi.nlm.nih.gov/27251227/



Martin

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