Euglena cells look like plant and animal cells at the same time

Its name means “true eye” and derives from the Greek terms eu , meaning “true”, and glene , meaning “eye”. They were named after the German zoologist and botanist Christian Gottfried Ehrenberg in 1830, who dedicated his life to the study of these organisms.

Characteristics

Euglena are approximately 45-65 microns long and 14-20 microns wide. They have a light-sensitive receptor and an eyespot. The eye spot is a structure formed by a membrane that includes granules composed of pigments that capture light. Next to the eyespot is an organelle known as a photoreceptor or photosensor. This receives the light that filters the eye spot and activates cell function.

Also, the single cell of many euglena contains bright green chloroplasts. When these microorganisms remain in the dark for some time, they lose their chloroplasts and feed heterotrophically, that is, engulfing particles or other organisms. If they are exposed to light radiation again, they can re-develop chloroplasts and thus carry out photosynthesis again.

cell anatomy

Euglena photosynthetic cell anatomy also includes:

• The plasma membrane, which surrounds the cell’s cytoplasm and protects its contents. This membrane has, in turn, a thinner membrane that surrounds it.
• The cytoplasm: it is a watery substance similar to a gel.
• A nucleus: it is the structure that contains the DNA.
• A nucleolus: it is inside the nucleus, contains RNA and allows the synthesis of ribosomes, which in turn, synthesize proteins.
• Chloroplasts: are organelles that contain chlorophyll and are responsible for absorbing light energy to carry out photosynthesis.
• The eyespot: This structure is usually red in color and has pigment granules that detect light.
• A photosensor: it is a structure that is very sensitive to light and detects it. It is located near the flagellum and participates in the movement of the cell both toward and away from light.
• Flagella: consist of two microtubules that allow cell movement.
• Mitochondria: are structures that generate energy for the functioning of the cell.
• Golgi apparatus: It is responsible for manufacturing, storing and moving certain molecules in the cell.
• Lysosomes: are sacs of enzymes that synthesize cellular macromolecules and detoxify the cell.
• Contractile vacuole: it is a structure that regulates the amount of water in the cell.

Habitat and feeding

The euglena genus lives in aquatic environments, both saltwater and freshwater. It is common to find these organisms in ponds, lakes, streams, and marshes. Also, they inhabit tiny spaces between grains of sand and other sediments at the bottom of the sea.

The type of feeding depends on the presence of light energy. If they are exposed to sunlight, their nutrition occurs through photosynthesis. From this process it obtains the necessary nutrients for its subsistence. In this case, their diet will be characterized by being autotrophic, that is, based on the production of their own food. During the night, or in the absence of sunlight, they may feed on other organisms or organic matter. In this case, the diet will be heterotrophic.

Motion

To move from one place to another, euglena have filaments known as flagella. They are located near the photoreceptor and face forward and backward. As their name implies, they are structures that resemble whips. By shaking them, they propel themselves and can move easily.

Reproduction

The life cycle of most euglena presents a free moving stage and a stationary stage. In the free-moving period, they reproduce rapidly through a method of asexual reproduction known as binary fission .

Through this type of reproduction, the cell reproduces its organelles by mitosis. It then divides to generate several daughter cells. When environmental conditions are unfavorable and too difficult to allow survival, euglena enclose themselves in a protective cyst consisting of a gelatinous substance. The formation of these protective cysts occurs during the immobile stage. When environmental conditions are favourable, the new cells develop flagella and exit the cyst.

Other interesting facts

In addition to their peculiar characteristics, there are other curious facts about euglena:

• They are a potential source of biofuel.
• Some euglena species have plant and animal cell organelles. For example, the species Euglena viridis and Euglena gracilis have chloroplasts just like plants, but they also have flagella and no cell wall, just like animal cells.
• Some euglena species change color from green to deep red, depending on the degree of exposure to sunlight.

Bibliography

• Mikoley, K. The Protists . (2020). Spain. Gareth Stevens Pub.
• Fester Kratz, R.; Siegfried, D. Biology for Dummies . Spain. Planet.
• Freeman, S. Fundamentals of Biology. (2018). Spain. pearson.