Spirostomum - largest of all ciliates

Bruce Williams · Post by **Bruce Williams** » Sat Dec 02, 2006 6:47 am

Hi folks,

Some photos of Spirostomum (largest of all the ciliates).

This individual frequently contracted down to about a third of its length when I accidentally knocked the fine focus knob. I have since read that Spirostomum contracts faster than any other known living creature. It's quite a slow swimmer (revolving along its axis) and really the main problem I had photographing it was picking the moments when all of it's long body was in focus.

Pic1 - This pic shows the whole animal facing right. You can just make out the short cilia that cover its body. The large, light area near the tail is the single contractile vacuole which is transparent enough to show the spiraling lines of cilia (lower inset).

Pic2 - The top half of the photo shows the head and what I believe is the peristome leadin to the mouth situated near the middle of the animal's body (slightly nearer the head). The bottom part of the photo shows some of the long nucleus which looks like a string of sausages. The nucleus was much more visible through the eyepiece.

Bruce

rjlittlefield · Post by **rjlittlefield** » Sat Dec 02, 2006 7:25 am

Bruce,

Nice pictures! How big is this creature anyway?

BTW, I was curious about that "contracts faster" claim.

Tracking it down, I see that at Wim van Egmond's site, it says

One of the remarkable things of Spirostomum is the way it can contract. The organism can contract it's body to 1/4 of it's length in 6-8 millisec which is the fastest contraction known in any living cell.

This number and its significance is repeated at many other sites, for example at Nikon's MicroscopyU.

But many other sources, for example this one, quote the wing beat frequency of a midge as over 1000 flaps per second. That's a cycle time of under 1 millisecond, and I suppose the muscle contraction phase is only about half that long.

Presumably all these facts are accurate. The question is, what's being compared to what? I can only speculate that Spirostomum has the fastest whole-body contraction of any single-celled creature, while midges have much faster contractions of the cells in flight muscles.

--Rik

PS. An interesting sidelight is that it's possible that all of the midge quotes actually trace back to a single publication from over 50 years ago. See this article for discussion.

Ken Ramos · Post by **Ken Ramos** » Sat Dec 02, 2006 10:15 am

Some nice photographs there Bruce

, I haven't seen any of these in a long time but then again I have not been using my Axiostar and looking at pond critters much. Defining the myonemes can be a real challange.

Bruce Williams · Post by **Bruce Williams** » Sat Dec 02, 2006 2:03 pm

Thanks for your comments Ken. "Myonemes" - so you've given me another new word to research on the web

Rik,

Your speculations re. fastest muscle contraction sent me on a very interesting half hour browse of the net. I must confess until I read your posting I had not thought about looking for a candidate outside of the protozoa.

Am posting another pic of Spirostomum with an inset showing Coleps for the purposes of scale.

Bruce

Cyclops · Post by **Cyclops** » Sat Dec 02, 2006 2:18 pm

Great photos of a cool beastie!

rjlittlefield · Post by **rjlittlefield** » Sat Dec 02, 2006 3:07 pm

Bruce Williams wrote:Am posting another pic of Spirostomum with an inset showing Coleps for the purposes of scale.

I'm sorry, I don't know Coleps either.

I noticed that one of the web pages said that Spirostomum got up to 4mm long, so I was wondering how big this one was.

Do you know how wide the picture is?

--Rik

Bruce Williams · Post by **Bruce Williams** » Sat Dec 02, 2006 3:28 pm

Hi Rik,

Coleps is typically about 70µm long so I would estimate that this individual is no more than 2mm fully extended.

Bruce