Euglena is a unicellular, eukaryotic organism. It belongs to the Kingdom Protista, and is the most widely studied member of the phylum Euglenophyta/Euglenozoa. It is found in freshwater sources like a quiet puddle or pond and can even be found in a swimming pool. Several species can produce breathing vesicles that prevent them from drying. It essentially serves as a source of food for marine critters and fish. It can be described as a type of protozoa having mixed characteristics of both plants and animals. It is similar to plants because it can prepare its own food by photosynthesis.
Its resemblance with animals lies in the fact that it can move around from one place to another and can eat food like animals by heterotrophy. It surrounds a food particle and consumes it by phagocytosis when acting as a heterotroph. It is known to have three modes of nutrition. The first is the holozoic mode which involves the intake of solid visible food. The second is the saprozoic mode which involves ingesting food in soluble form. The last is the holophytic form in which, using photosynthesis, a protozoan is able to synthesize complex organic compounds. The Kingdom Protista also consists of other life forms such as amoeba and paramecium.
Interesting Facts about Euglena
This single-celled-organism has a number of organelles to carry out various important bodily functions. Besides this, it has other biological features which make it a distinctive creature.
- Euglena has an oval-shaped body structure with a round anterior and tapered posterior. The outer part of its cell membrane consists of a stiff pellicle which enables it to maintain its shape.
- The bright green body color of this organism is due to the presence of chloroplasts inside its cell. Euglena's chloroplasts are quite unique because they are surrounded by three membranes, while those of plants have only two membranes. Unlike plants, this organism lacks a cell wall made of cellulose. Rather, it has a pellicle which is made up of a protein layer supported by microtubules. It is arranged in strips spiraling the entire cell. In fact, its marvelous flexibility and contractility is attributed to the action of these pellicle strips, sliding over one another.
- The chloroplasts are known to contain pyrenoids which are used in the synthesis of paramylon. This paramylon, a form of starch energy storage, helps the organism to survive long periods of light deprivation. The presence of pyrenoids is the most distinctive feature of this genus.
- All Euglenoids possess two flagella rooted in basal bodies. One flagellum is very short (does not protrude from the cell), while the other is a long, whip-like thing attached on the right side, towards the front of the body. This long flagellum works as a propeller and helps it to move through water.
- The central part of the cell is occupied by the nucleus which is purple in color. It carries the DNA of the cell and is involved in several vital cellular activities. The nucleolus (plural nucleoli) present inside the nucleus can be identified with its pink color. The inner part of the cell is filled up with a light yellow-colored viscous fluid known as cytoplasm.
- A distinguishing characteristic of Euglena is that it is both autotrophic as well as heterotrophic. In other words, it can produce its own food using photosynthesis, but it also consumes food from its environment when enough sunlight is not available. In that case, it moves around in the water and eats other microorganisms like amoeba and paramecium.
- When food is scarce or in low moisture conditions, Euglena forms a safety wall around itself. During this period it lies dormant as a resting cyst till the environmental conditions improve.
- Another interesting physical feature is the red eyespot. This is a pigmented organelle found at the anterior part of the body and is highly sensitive towards light. This adaptation is extremely important as it helps to detect sunlight which is needed for photosynthesis. Once the sunlight is traced by the eyespot, the organism can orient its movements in that direction, a process known as phototaxis.
- At the rear end of the cell, there is a star-shaped structure called the contractile vacuole which is orange in color. It helps in the excretion of excess water and wastes from the body. In the absence of this organelle, it would have sucked up enough water through osmosis causing the cell to explode.
- These organisms reproduce by a process of cell division known as mitosis. During this process, the cell divides into two halves longitudinally, beginning at the front end of the cell. It also leads to the duplication of gullet, stigma, and flagellar processes. Thus, two new Euglenas are formed from one. Favorable conditions for the multiplication process are a warm atmospheric temperature and adequate amount of food.
After reading all these interesting facts, you must be excited to see these creatures for yourself. However, they are so tiny that they cannot be seen with the naked eye. You have to use a microscope in order to see them closely. When millions of them gather in one place on the surface of a pond, they look like a mat. This appears quite similar to algae. They help in maintaining a balance in the environment by taking in carbon dioxide and releasing oxygen. They contain a large amount of carotenoid pigment. So, if you find the water in a marshy area appearing a bit reddish, it is quite possible that it is due to the presence of Euglena.