Life in the moss: rotifers

I spent Easter of 2011 at my brother's house in Wayland, Massachusetts. The weather was damp and cool the first day and Tina and I took a short walk on the country roads in the area, by pastures and stone walls of the gentleman farms. The area has a sandy soil and pine oak forests. Along the way I collected a discarded water bottle and a couple pieces of moss. I added a little water and allowed the moss to soak over night.

Easter Day was a bit more sunny. The Moss sample had soaked over night in a small dish of water made by cutting the bottom off of the plastic water bottle, about 1 cm deep and 3-4 cm in diameter. This is one technique for looking for Tardigrades or water bears. I was slightly hopeful that I might locate some, but that was not to be. One resource that I read mentioned that the Tardigrades require a source of calcium, but these sandy soils may be a little short on that resource.

I prepared a sample by swirling the pin cushion of moss in the water then drawing out the water and placing about 10 drops on the glass stage of the Bancks 1825 microscope. I set up the scope in the kitchen, thanks Cathleen, and used the ambient light of the room to illuminate the sample. Many took a look, including my mother. :) I used the number 2 lens, the highest magnification lens in the set (the #1 lens was lost before I acquired the microscope).
The moss did contain a large population of rotifers, small multi cellular animals with a remarkable complexity. They were very mobile, inching along grasping the substrate with their posterior "toe" and anterior end with Ciliary Corona retracted inside the body.

They will settle down once in a while, anchored by the toe, and unfurl their Ciliary Corona and commence beating the cilia generating a current about the mouth end, drawing in food. I found one large rotifer that was settled in and feeding. I used my camcorder set on "Tele-macro" and managed to film some video through the number 2 lens.

I have included two of the videos here.





This video shows the beating cilia and food particles being drawn in and ingested. The food travels down to the mastax where it is chewed and passed to the stomach. This video does not show the full field of view seen through the microscope, it is less than half of the full field, and the image quality is poorer than that seen by the naked eye. The quality of the video was challenged by lens glare and movement of the hand held camcorder. At the end of the video the footsteps of a passer by startled the rotifer causing it to retract its ciliary corona and then redeploy it. I think that this video shows the anus of the rotifer in an open state, closing, and the contents of the intestine moving.