Vorticella : Post separation stalk contraction movies

Thomas Ashcraft · Post by **Thomas Ashcraft** » Fri Nov 23, 2007 11:22 am

Hi Microscopists.

Inspired by Charlie's Vorticella stalk and myoneme images I am posting links to a couple of movies of Vorticallas separating from their stalks with the stalks then contracting right after separation.

http://www.heliotown.com/Vorticellas_De ... Stalk.html

Tom in New Mexico

Charles Krebs · Post by **Charles Krebs** » Sat Nov 24, 2007 12:41 pm

Tom,
You really captured that perfectly! Excellent. Looks like a situation where they both wanted to look for a more satisfactory environment.

bernhardinho · Post by **bernhardinho** » Sat Nov 24, 2007 3:11 pm

Nice, Tom

the second video looks like the final stage of a cell division!

Bernhard

Thomas Ashcraft · Post by **Thomas Ashcraft** » Sun Nov 25, 2007 9:19 am

Charlie wrote: "Looks like a situation where they both wanted to look for a more satisfactory environment."

Hi Charlie, Hi Bernhard,

Yeah, maybe they were camera shy.

Tom

rjlittlefield · Post by **rjlittlefield** » Sun Nov 25, 2007 10:03 am

with the stalks then contracting right after separation

Actually the stalks contract right before separation.

I'm often interested in what you can tease out of videos by doing frame-by-frame "instant replays" and "stop actions".

In the second video, at normal speed, final separation seems to occur at exactly the same time as a sudden contraction of the stalk.

Was the contraction caused by the separation, or the separation by the contraction, or were they just too close together to call?

Displaying the .mp4 in QuickTime and using the arrow keys to navigate frame-by-frame gives quite a bit more information.

What turns up is a frame in which the contraction has just started. The blur pattern shows that while both bugs are being jerked back, the bug on the right has been jerked about twice as far. (This is the bug that remains connected to the stalk after the contraction is over.)

From this frame, it seems pretty clear that the bug on the left was still attached at the start of the contraction, and came loose part way through.

I went back to the first movie to take another look, and found the same pattern there. Of course there's only one individual to look at, but there are also two frames in which the first frame shows the stalk still connected to the bug, while the second frame shows it obviously disconnected but the bug has been jerked backward quite a bit.

It's tempting to interpret this in terms of the contraction causing the final separation in these cases.

But for all I know, it could be that all separations look like this, and the contraction is actually triggered by some near-the-end bit of activity in closing off the membrane in preparing to separate. (If they do all look like this, I have no idea how you'd ever tease apart cause and effect, or for that matter, why anyone would care enough to try.)

Neat videos, in any case!

--Rik

Thomas Ashcraft · Post by **Thomas Ashcraft** » Sun Nov 25, 2007 10:16 am

Rik wrote: "Actually the stalks contract right before separation."

Hi Rik,

Very interesting analysis. Neat.

I think my Canon S3 IS will also shoot movies at 60 fps. When I come across action like this in the future maybe I will switch into faster mode to see what's there.

Tom