The photo of a testate amoeba's shell (Euglypha) was taken using a scanning electron microscope. If the amoeba was alive, it would protrude from the open end. The shell is approximately 0.04 mm long. Testate amoebae are large Cercozoa. Small amoeba-like Cercozoa (https://www.youtube.com/watch?v=gRsEES1e3HQ) can be down to 0.003 mm long. testate amoebae appear to be sensitive to the type of drier climate that we expect in the future.