The organism can vary in shape from short or elongated spindle to cylindrical or band-like. Its outer covering (pellicle) often shows longitudinal or spiral markings, with some species having a flexible pellicle. The stigma, a light-sensitive organelle, is typically positioned at the anterior end. Chromatophores, responsible for photosynthesis, are numerous and can be disc-shaped, band-shaped, or spindle-shaped. Pyrenoids, which aid in starch storage, may or may not be surrounded by a starch envelope. Paramylum bodies, used for energy storage, may appear as two structures located near the nucleus or scattered throughout the cell. A small contractile vacuole is located near a reservoir, assisting in osmoregulation. Asexual reproduction occurs through longitudinal fission, while sexual reproduction has been observed in Euglena sanguinea. These organisms thrive in stagnant water where algae are prevalent. In large numbers, they can form a green film on the water surface, and resting stages or cysts may create conspicuous green spots at the bottom of ponds or pools. They are commonly found in freshwater environments.