Wednesday, July 04, 2007

In the Bay 3 July 2007

Since I wrote about marine cilliates in my previous post, I thought I'd try to find some for this edition of In The Bay.

This is a group of Vorticella or Vorticella-like stalked cillates. As you watch the movie you can see the feeding current they are creating with their cillia. About 21 seconds into the movie (6 seconds from the end) the whole colony retracts. This is a defensive mechanism and occurs extremely fast.


Kevin Z said...

Great Movie, did you film this yourself? I love watching protists under the scope. Do you know what the mechanism for retracting is? Biomechanically I mean. Its not like other tube-dwellers (polycheates for instance) where it is controlled by musclature.

Andrew Staroscik said...

Yes they are my films. I have a leica microscope with phase optics and an adaptor for a digital camera.

I think the mechanism is known. If I recall correctly it is a spring-like mechanism that allows them retraction to occur so quickly.

Here is a science paper describing the retraction structure. A quote:

"The spasmoneme is a bundle of filaments, each 2 nm in diameter (Fig. 1B). Although the structures of a filament and of the bundle are unknown, birefringence measurements (4) show that the extended spasmoneme is composed of roughly aligned but weakly cross-linked filaments. Shrinkage and swelling of the spasmoneme in the absence or presence of calcium (6)...Contraction is amplified by the number and linear arrangement of the subunits in the polymeric network that form the contracting organelle. Because the spasmoneme is helical, it rotates during contraction. This interplay between twisting (or bending) and extension is a recurring theme in all mechanochemical springs."