Rotifers - Some of the smallest animals on earth

Rotifers are some of the smallest animals on the planet. Most measure under 500 microns, but their size can range from only 50 microns to around 2 mm (2000 microns). They are some of the most common microscopic animals, living all over the world in all kind of environments, like freshwater, saltwater, in moss on trees and in the soil underneath your feet. Rotifers are made up of roughly 1000 cells, some of which are specialized to form organ systems. Despite their incredibly small size they have eyes, a small brain and nervous system, and a dedicated digestive system just like us.

A better image for your stereo microscope

In compound microscopes, an illumination parallel to the optical axis is the standard. A lot of hardware is implemented to ensure this axial illumination: Center-adjustable Field and Aperture diaphragm, centerable light rings for Phase contrast and Darkfield for transmitted light, center-adjustable objectives and/or centerable rotatable stages in Polarization microscopes. With all these microscopes we are working on 2-dimensional samples.

In stereo microscopy, a 3D image from a 3-dimensional sample is our ambition. Different viewing angles for both eyes create different images on the retina of the left and the right eye. Our brain is going to process both images. This concept is best comprehensible in the Greenough construction of a traditional stereo microscope: two complete separate beam paths from objective to the eyes, mounted in a relative angle of 11°-16°. But even in the modern, more flexible CMO (Central Main Objective) concept a different viewing angle is realized.

Greenough type                       CMO (Galilean) type 

Cytoplasmic streaming in onion cells

All cells are confined by a cell membrane, and in the case of plant cells this membrane is accompanied by a cell wall. Inside this envelope, each cell contains a lot of different organelles, molecules like proteins, carbohydrates and nutrients along with a cytoskeleton for structural support.

The organelles and macromolecules need to move around to get where they are needed. One way of achieving this is through passive diffusion. However, this process is very slow in the crowded cellular cytoplasm where up to 30% of the volume is taken up by macromolecules. To speed things up the cell utilizes a phenomenon called cytoplasmic streaming, also known as protoplasmic streaming and cyclosis. This kind of molecular movement, in contrast to diffusion, is not a passive but an active process which uses energy in the form of ATP (adenosine triphosphate). The energy is spent on moving specialized transport molecules called myosin, kinesin and dynein, along the cellular cytoskeleton while carrying the macromolecules and organelles.