Euglena sanguinea is a species of the genus "Euglena". Recognizing the polyphyletic nature of the genus "Euglena," Marin et al. Another unicellular form of movement shown in Euglena is known as metaboly. It can be seen in many microorganisms including Euglena. Paramylon is made in the pyrenoids of "Euglena". Euglena gracilis is a freshwater species of single-celled alga in the genus "Euglena". Species of "Euglena" are found in freshwater and salt water. The photoreceptor protein in "Euglena" is likely a flavoprotein. Their shape is often characteristic of the "Euglena" species that produces them. For example, flagellate protozoans of the genus "Euglena" move towards a light source. Species of "Euglena" were among the first protists to be seen under the microscope. "Euglena gracilis" is a motile, freshwater, photosynthetic flagellate. The eyespot apparatus of "Euglena" comprises the paraflagellar body connecting the eyespot to the flagellum. The species "Euglena gracilis" has been used extensively in the laboratory as a model organism. Euglena is a genus of single cell flagellate eukaryotes.