The motion of the cilia on certain rotifers (especially the bdelloid and limnias) have fascinated me since I observed it for the first time. It was a major impetus to setting up an electronic flash almost as soon as I set up my microscope. I've taken far too many pictures of this subject already, but can't resist trying to get one just a little better than before.
The top image is one of the occasions where many elements happened to work just right. I was using a "high/dry" 63X objective with a correction collar. It's always tough to "set" this correction just right with a subject that is in constant motion, and constantly moving closer and farther from the coverslip. The body position of the subject is critical since the slightest "wrong" angle to the head can throw most of the picture out of focus due to the shallow DOF. Not to mention trying to track, frame and focus a moving subject. So you just keep taking pictures as fast as you can and hope that you get one where it all works out. The lighting for this top image was oblique brightfield. It worked well, giving a pretty "life-like" 3D effect.
The lower image was taken using "regular" brightfield. These rotifers can create quite a current when feeding. On this slide there were a good number of haematococcus (thanks Wim... didn't know what they were until your post!) floating around, and they were continually drawn to the rotifer. Sort of a nuisance for the rotifer, since this is not "food" for her, and the haematococcus just get in the way of feeding. But it made a sort of comical shot, as if it were playing with a beach ball.
