Phototaxis in Euglena algae. Light microscope differential interference contrast (DIC) footage of Euglena sp. algae demonstrating phototaxis (movement stimulated by light). Euglena is photosynthetic, using the energy of sunlight to synthesise food. The characteristic red eyespot is sensitive to light, allowing it to move towards sunlight. When the field diaphragm of the microscope is narrowed (start of clip), the Euglena cells move into the lighted area in the middle of the field of view. When the diaphragm is opened at the end of the clip, the cells move outwards and re-distribute across the increased field of view. Magnification: x195 at 10 centimetres across.