feeding vortices

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Martin Parnham
Posts: 31
Joined: Thu Oct 06, 2022 2:43 pm

feeding vortices

#1 Post by Martin Parnham » Wed Nov 30, 2022 4:37 pm

Hi folks - You often get glimpses of the vortices generated by Ciliates whilst moving / feeding. You need a bit of luck and enough 'small bits' to be swept up to see the motion of the water. I have been experimenting with adding particles that would make observation clearer. I have tried various powders, grinding with pestle and mortar etc. I eventually found a reasonable solution. Homogenized whole milk seems to work well!
Most supermarket milk here in the UK is sold homogenized. The tiny sub-micron fat globules remain in suspension under a cover slip and are readily visible. Whole milk works best (3.7% - local supermarket whole milk). It reduces the amount you need to produce enough fat globules to observe whilst reducing the amount of extra solutes from the milk which may osmotically affect the microbes. A dilution of 40 :1 produces good results, so simply 40 drops specimen water to 1 drop milk (add milk last and use the pipette to stir in). There are enough globules to be easily seen, but not so many to badly hinder the movement you are trying to observe. Looking at the pumping rate of the contractile vacuoles seems to suggest no untoward osmotic effects.
Oblique illumination works very well with this technique, I simply pull / rotate my filter holder containing my usual dark field stop slightly to one side.
All videos filmed real time with no post recording image processing. Brunel SP300 microscope, plan, achro, infinity, oblique lighting and recorded on a Samsung Galaxy A13 phone.

The first video shows Vorticella feeding. The vortices are impressive, they extend many body lengths from the organism with an impressive rate of flow. The globules swept through form what can only be described as a 'jet stream'. Notice also the very rapid contraction of the stalk - the organisms escape response.
This link is to an interesting paper where all this is discussed from a biophysics / engineering point of view.

https://drpepperlab.files.wordpress.com ... icella.pdf

(0:00 to 0:52) x10 Obj, (0:52 to 1:18) x20 Obj, (1:18 to 1:50) x40 Obj, (1:50 to 2:18) x60 Obj (Hard to film!)





The other videos show vortices generated by Paramecium -

(0:00 to 1:00) x10 Obj, (1:00 to 2:14) x20 Obj, (2:14 to 2:24) x40 Obj




Euplotes -

(0:00 to 0:12) x10 Obj, (0:12 to 0:35) x20 Obj, (0:35 to 0:54) x40 Obj





and a small ciliate (?) -

(0:00 to 0:37) x40 Obj, (0:37 to 0:53) x20 Obj



PS - The globules show no birefringence, polarization adds little to the image.It might be interesting to see the technique using phase and also DIC - Hint hint.
Other ciliates and microorganisms are available ! – Another hint.

Martin

Chas
Posts: 422
Joined: Tue Jan 19, 2021 3:11 pm

Re: feeding vortices

#2 Post by Chas » Wed Nov 30, 2022 8:09 pm

This is just brilliant.... thanks.
The concentration of the milk droplets behind the vorticella is really surprising to me.
I have been wondering how vorticella can influence the water flow so far away from itself
..but somehow if the flow at this size/Reynolds number is dominated by viscosity rather than momentum ..in my mind I think of treacle, yet I couldnt get treacle to move ten bodly lengths away from me at such speed.
(Clearly, I misunderstand!!)
I cant wait to try the milk !

Martin Parnham
Posts: 31
Joined: Thu Oct 06, 2022 2:43 pm

Re: feeding vortices

#3 Post by Martin Parnham » Thu Dec 01, 2022 7:48 pm

Hi Chas - thanks for that.

I think you are spot on with the viscosity issue. I think that generating vortices such as many ciliates produce must be a tremendously energetic process. I suspect that a very significant portion of their ATP generation is dedicated to it. Its one of those evolutionary' conundrums' - they have to generate large feeding vortices in order to get enough food to provide the energy to carry on producing the feeding vortices............... They must also use a lot energy for osmoregulation, they have to continually pump water out as it floods in due to osmosis, coupled with maintaining their cellular structure, whole organism locomotion and occasionally reproducing these so called 'simple creatures' are very sophisticated self sustaining systems.

Martin

MichaelG.
Posts: 3976
Joined: Mon Apr 10, 2017 8:24 am
Location: North Wales

Re: feeding vortices

#4 Post by MichaelG. » Fri Dec 02, 2022 12:32 am

.

Superb demonstration, Martin

MichaelG.
Too many 'projects'

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