Why are euglenas green? Is euglena a green algae?

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Why are euglenas green? Why do euglenas look green?

It is to be noted that not all Euglenas are green in appearance. Amongst the 800 different species in 54 genera, most of the euglena species like Euglena viridis, Euglena gracilis, etc. appear green in color while others like Euglena sanguine, etc. appear red in color.

Those Euglena species that appear green in color have photosynthesizing chloroplasts with chlorophyll pigments within their cell body that gives them plant-like characteristics.

In fact, the chloroplast organelle help the Euglena consume (absorb) the sunlight to produce food autotrophically via. the process of photosynthesis.

Euglenas can also eat green algae, amoebas, parameciums, and rotifer through a method called phagocytosis.

And so, their green color not only comes from the green chloroplasts they have but also comes from the green algae they eat.

They are called Autotrophs because they can produce their own food. The chloroplasts in Euglena gives it the ability to provide nutrients for itself through the process of photosynthesis.

Chloroplasts due to the chlorophyll pigments cause the green-colored appearance to the Euglena.

Chlorophyll is green leading to the green appearance in Euglena as chlorophyll does not allow the absorption of the green wavelengths of white light. So the green wavelength is reflected from the plant, and so Euglena appears green.

In Euglena, the chlorophyll pigment absorbs energy from the sunlight. Then, with the help of sunlight energy the Water (H2O) reacts with Carbon dioxide (CO2) in a series of steps forming a Hexose Sugar.

This Hexose Sugar is then transformed into a type of polysaccharide, called paramylum or paramylon.

Paramylum (a form of starch) is a polymer made by Euglena to store energy. They use energy from sunlight to make a simple sugar called glucose.

Euglena gracilis

This is an image of several Euglena gracilis cells taken using light microscopy.
Ellis O’Neill / CC BY-SA

Is euglena a green algae?

No, euglena is not a green algae. In fact, euglena is believed to have been originated from green algae as per the morphological pieces of evidence are concerned.

People often consider Euglena and green algae the same. It’s because they both dwell on the surface of stagnant water and gives a green-colored appearance to the water surface.

One of the notable differences between Euglena and Green algae is that Euglena can be both heterotroph and autotrophs, but algae can only be autotroph.

Euglena can act like heterotrophs when sunlight is not available. They get their food from the products of decaying organic substances that are dissolved in the surrounding water and absorb those through its general body surface that is, mainly through the pellicle.

Both euglena and algae are two different plant-like protists amongst the at least 100,000 kinds of protists that are known so far.

The green algae are autotrophic protists that can be either unicellular or multicellular. Whereas, all Euglenas are unicellular organisms classified under the Kingdom Protista.

Euglena lacks a cell wall, having a pellicle layer supported by a substructure of microtubules, arranged in strips spiraling around the cell. Whereas, green algae have cell walls containing polymers similar to that of the land plants.

Euglenas are single-celled organisms and thus cannot be seen with the naked eye. Green algae can be seen with naked eyes.


What is the purpose of euglena? What is it’s advantage of being green?

What is the purpose of euglena?

The photosynthesis performing ability of Euglena at the micro-level makes it beneficial for the environment as it can utilize the sunlight and take in carbon dioxide and release the oxygen into the atmosphere so that other organisms can survive.

Euglena if taken as medicine can reduce body fats and cholesterol, improve the body’s immune system, and also can reduce the level of uric acid in the blood.

The different species of Euglena also function at several levels of the ecological food web either as producers, or consumers, or decomposers.

Euglena can be both a friend and a foe. Euglena is not only good, but also bad for the environment.

What is its advantage of being green?

The advantage of Euglena being green is that it can absorb energy from the sun to undergo the process of photosynthesis in order to prepare its own food.

Euglena can make their own food and so are called producers. They pass the energy to the next trophic level that is to the primary consumers, then to the secondary consumers, then to the tertiary consumers, and then to the decomposers.

Due to having chloroplast, Euglena is green in color and so it can grow by converting CO2 into biomass through photosynthesis, thus reducing CO2 emittance in the environment.


Is euglena a plant or an animal?

Euglena includes those microorganisms that feature both plant and animal characteristics. Euglena falls in the group of both plant-like or animal-like protists.

Euglena is both plant and animal-like because like plants Euglena can perform photosynthesis using chlorophyll. And like animals, they can also move around and eat saprophytically.

So, that’s why it is said that Euglena lies in the fact that it behaves like a plant in the presence of sunlight, but in the dark it behaves like an animal.

It’s true that Euglena is both animal-like and plant-like but it cannot be considered a true plant or a true animal because it does lack a cell wall which is a defining feature of plant cells, instead having a pellicle made of protein bands to protect itself.

When in light, Euglena will use its chloroplasts to help produce food from sunlight, water, carbon dioxide, or other chemicals using the process of photosynthesis.

When in the absence of light, it becomes distinctly animal-like. It will use its pellicle layer to get the food from dead and decaying matter using the process of phagocytosis.

Euglena cells have flagellum on cells which allow the cells to move and are the characteristics of animal cells. It also has a contractile vacuole like in Amoeba.


Do euglenas eat green algae?

Yes, Euglenas can eat green algae by the process of phagocytosis due to being heterotrophic.

Biologists also refer that the green coloration of Euglena is because they eat green algae and keep it inside their bodies.

Although they have their own chloroplast organelle inside their cell, they can also utilize the chloroplast of the eaten green algae to perform photosynthesis and appear green.

At the 40x lens microscope, Euglena appears like tiny (minute) particles making small movements in the water.

As magnification increases to 100x and 400x, you will notice that they appear green to light green in color with dark spots inside the cell.

Along with algae and other protists, Euglena remains on the water surface in the form of algal bloom.

So, the next time, you see a polluted pond, lake, or still body of water with a green or red film-layer over the water surface, then it’s most probably due to the presence of euglena along with algae.

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