Euglena Under The Microscope: Structure, Morphology, And Classification

Belonging to the protist genus, Euglena are single-celled organisms. While they are not considered animals, plants, or fungi, they do share a few characteristics with animals and plants.

Like plants, they can produce their own food, but like animals they are also able to move.

Euglena Under The Microscope: Structure, Morphology, And Classification

Euglena is also known to have an eye-spot at the anterior end that allows them to detect light.

So it’s safe to say already that Euglena is pretty fascinating! But what are its characteristics and morphology, and can Euglena be beneficial to humans? Read on to find out!

Euglena Microscopy

As they are single-celled organisms, Euglena are not visible to the naked eye. To view them, you need a compound microscope in order to observe and study them.

Their natural habitat is algae or pond weed, and as they live in ponds (or any shallow water that contains organic material) they are quite easy to collect and view under a microscope. 

Preparing Euglena To View Under A Microscope

As we’ve already mentioned, it’s pretty easy to view Euglena under a compound microscope if you’ve collected directly from pond water.

However, if you’ve collected Euglena from pond weed, then you can conduct a simple culture experiment in order to increase their numbers. Here are the steps you need to follow in order to do this:

  • Gather some pond weed from any pond (ideally Ceratophyllum).
  • Put a couple of pond weeds in a petri dish or a jar and pour water over the pond weed.
  • Leave the jar in a dark room for a couple of days until a brown scum forms on the water’s surface.

What You Need For Microscopy

  • A compound microscope.
  • Microscope glass slides.
  • Microscope cover slips.
  • A dropper.

Use a dropper to collect some pond water or the brown scum from the culture, and place a drop on the microscope glass slide.

Then carefully place the cover slip on the sample and place the slide on the microscope stage.

Observing Euglena

When viewing Euglena under the microscope, you should be able to see the amoeba and Euglena, as both are very common in pond weed and water.

But this isn’t too much of an issue, as amoeba can be differentiated from Euglena, as Euglena have a tail that looks like a whip on one end. This tail is small and transparent, and you have to look carefully to spot it.

When viewing Euglena at 40X, Euglena looks like tiny particles moving in water.

When you increase the magnification to 100x and 400x, they begin to take on a green to light green shade, and as well as their whip-like tail you can see dark spots. 

A higher power microscope will also reveal colored granules, also known as the eyespot. 

Euglena Structure And Morphology

Shape And Flagella

When you look at Euglena under a light microscope, you’ll see a long, single-celled organism that is moving quickly across the field surface.

You’ll notice at first glance that the Euglena has a rounded end and a teardrop, pointed end. Not all Euglena look like this, but this is their common appearance. 

The rounded end is considered the head of the Euglena, and the tail is known as the flagella. Because they have a flagellum, Euglena are also referred to as flagellates.

You may only notice Euglena has one flagellum, but it actually has two. You don’t see this as it is usually concealed in the reservoir of the Euglena. 

It is the longer flagellum at the anterior end of the Euglena that makes it possible for them to move in the water, as it twirls quickly – like a propeller!


While plant cells have a cell wall, this species does not. Instead, the organelles of Euglena and its cytoplasm are bound by a plasma membrane that lets the Euglena move easily. 

When viewed under a powerful electron microscope, people have found ornamented pellicles under the plasma membrane.

This thin layer keeps the cell membrane safe and helps the Euglena to maintain its shape. Plus, it’s flexible, which further aids Euglena’s movement. 

The pellicle under the membrane is made up of a protein layer, supported by microtubule structures.

These tubules spiral around the cell and when they slide over each other these tubules become more flexible, which allows the Euglena to get into tiny spaces. 

Chlorophyll And Eyespot

If you look closely at Euglena you will notice a red spot on the anterior. This is a significant organelle with carotenoid granules.

These make Euglena sensitive to light and let it move towards sunlight. 

This eyespot also filters the wavelength of light that reaches the paraflagellar body. This is the structure found at the base of the flagellum that detects light.

The Euglena then moves towards the light for photosynthesis, and this movement is known as positive phototaxis. 

As well as the red eyespot, you may also notice dark green spots all over the Euglena. Some spots are chloroplasts. These contain chloroform and are responsible for the green hue and enable photosynthesis.

These are usually known as chlorophyll A. Meanwhile, some Euglena possess both chlorophyll A and B.

Chlorophyll B makes the Euglena bluish green and helps the Euglena produce more light for photosynthesis.

As Euglena is able to make their own food with sunlight and photosynthesis, this means that they are autotrophic organisms.

But while Euglena can make their own food, they also consume food, which makes them heterotrophic. Heterotrophs consume food via phagocytosis. 

Euglena sometimes engulf the food particle in a vacuole so they can digest it. Enzymes are released in the vacuole so the food particles can be digested.

They also have a contractile vacuole which helps them to collect and get rid of excess fluids from the cell. This makes sure the cell doesn’t absorb too much water, as too much water can break the cell.

Euglena Characteristics

Euglena Characteristics

While they share their characteristics, Euglena are neither animals or plants.

Since they cannot be grouped as an animal or a plant, they are instead classified under the Kingdom Protista, like other single-celled organisms.

Euglena are of the order Euglenales, and they belong to the family Euglenaceae.

What Can Euglena Be Used For?

Microalgae are fascinating because of the antioxidants, minerals, proteins, vitamins and polyunsaturated fatty acids that give them high nutritional value. 

Euglena gracilis is also an exciting alternative supplement as it’s a source of lipids, pro-vitamins, dietary protein and the β-1,3-glucan paramylon.

Studies have even shown that microalgae biomass may be a possible substitute for fish meal and soybean.

The characteristics of Euglena and how it is able to create unique and diverse bioproducts mean there is now a big push to develop Euglena gracilis bioproducts, and new companies are sprouting up all the time that specialize in Euglena cultures.

The cultivation method of Euglena has had a significant effect on the total protein content.

The most popular method of cultivating Euglena is the photoautotrophic method, as it is cost-effective and simple to manage, with a maximum yield of 0.5 g/g DW.

Meanwhile, heterotrophic cultivation is a lot more costly, but it is able to provide higher biomass and paramylon yield closer to 0.7 g/g DW, so their industrial potential could be realized sooner than we think! 

Biofuel production is not quite there yet, but the development of carbohydrate and lipid yields of Euglena gracilis may lead to it becoming a cost-effective alternative to traditional fossil fuels.

However, these are not the only advantages of using Euglena bioproducts! Euglena gracilis can also make animal feed more nutritious, and boost the osmosis of CO2 emissions in the atmosphere, thanks to carbon dioxide fixation.

Why is this so important? Because it can alleviate the impact of greenhouse gases and be a critical, important step in fighting climate change.

Scientists have already looked into what effect Euglena has on CH4 emissions by mixing varying concentrations of Euglena in animal feed.

The results found a drop in methane emission by 9-48% with concentrations of 100 g/k6 DM (or dry matter).

Euglena gracilis in this concentration was also found to have made dry and organic feed easier for animals to digest.

If research continues in this way, it could pave the way for many crucial developments, such as increasing the nutritional value of the food we eat as well as livestock.

It could also lead to the potential creation of mechanisms and biofuels to alleviate the effects of climate change, which would be game-changing as CH4 emissions decrease.

Another surprising fact about Euglena is that they might be immortal… yes you read that correctly!

What this means is that they don’t age, and scientists have carried out numerous experiments to prove this. 

For example, cell-population growth rates remained the same in cultures of Euglena gracilis that were not subject to senescence (the termination of cell division), and DNA patterns did not change during the continual growth of these cultures.

This is noteworthy because the defense mechanisms used by the algae to protect against stress could be beneficial for anti-aging technology.

Final Thoughts

In conclusion, Euglena is made up of microscopic eukaryotic organisms that are shaped like an oval, with chloroplasts that help the Euglena create their food, and two flagella that let them live in freshwater, saltwater, and even moist soil.

Euglena are able to create their own energy using photosynthesis, but if the light conditions they live in demand it, they can also eat other microorganisms.

The Euglena genus has some fascinating species, such as the Euglena gracilis which has been heavily studied because of the potential improvements it could make to the nutritional value of food for livestock – and humans!

In the not so distant future it may also be used as biofuel and reduce greenhouse emissions. Meanwhile, other species of Euglena are impressive too, and are able to survive severe conditions. 

One species of Euglena is also able to produce a toxic alkaloid known as euglenophycin that when exposed to fish and other algae can kill them.

But it might also have properties that can fight against cancer. 

People may be quick to write off Euglena as pond scum, but this single-celled organism clearly has a lot to offer!

Jennifer Dawkins