Closterium is easy to spot and identify under a microscope. Its green chloroplasts and crescent shape are unmistakable identifiers. The poles (ends) of the cell contain granules of gypsum, and with a steady eye and good magnification one can see the granules vibrate.

I got an added bonus on this photo. I had the Closterium positioned nicely at the tip of the pointer when an Amoeba slithered into view and pushed it off-center. I thought it would make a better photo with the two specimens together, so I snapped it anyway.