Euglena Under The Microscope
Structure, Morphology and Classification
Euglena are single celled organisms that belong
to the genus protist. As such, they are not plants, animal or fungi. In
particular, they share some characteristics of both plants and animals.
While they can manufacture their own food, a characteristic seen in plants,
they are also capable of movement and also consume food, which are characteristics
* Euglena also has been described as having an
eyespot at their anterior end that serves to detect light.
Euglena are single celled organisms and thus
cannot be seen with the naked eye. For this reason, a compound microscope has
to be used to observe and study them. They can be found in algae or pond weed
in pond water.
The organism can be found in water (ponds,
shallow water surface etc) that contains organic material. They can therefore
be easily collected and prepared for viewing.
If collected from pond water, Euglena can be
viewed directly under a compound microscope. However, if collected with pond
weed, then students can carry out a simple culture experiment to grow and
increase their numbers.
This involves the following simple steps:
- Collect some pond weed near
any pond (Preferably Ceratophyllum)
- Place a few pond weeds in a
jar or petri-dish and add water (cover the pond weed with water)
- Place the jar in a dark
room for a few days until a brown scum forms on the surface of the water
Requirements for Microscopy
Using a dropper, obtain some pond water or the
brown scum from the culture and place a drop of the sample on a microscope
Place the cover slip gently on the sample and
place the slide on the microscope stage for observation.
When viewed under the microscope, the slide will
show both amoeba and Euglena as they are common in pond water and
pond weed. Although students can also see amoeba in the sample, it is possible
to differentiate them from Euglena. Here, students will observe them (Euglena)
as elongated organisms with a whip like tail on one end.
At 40X, Euglena appear
like tiny particles making small movements in the water. As
magnification increases to 100x and 400x, students will notice that they appear
green/light green in color with dark spots inside as well as a whip like tail.
Higher power will also show colored granules, which are referred to as the
* The whip-like tail at the front end of the
organism is small and colorless (transparent). Students have to look carefully
to see them.
Euglena Structure and Morphology
Shape and Flagella
When viewed under the light microscope, Euglena
appear as elongated unicellular organisms that are rapidly moving across the
field surface. One thing that students will notice as soon as they begin to
observe the organism is that it has a blunt (rounded) end portion and a pointed
end (this gives them a tear-drop shape). Although this is not the case with all, it is the most common appearance.
The blunt, more rounded end is often
the "head" part from which the whip-like tail (flagella)
is attached. because of the presence of a flagellum, Euglena are also known as
Although one flagellum is often seen, they have two flagella,
one of which is often hidden in a part of the Euglena referred to as reservoir.
*The longer, visible flagellum located at the
anterior end of the organism twirls rapidly making it possible for these organisms to
move across water surface
Unlike most plant cells, this species do not
have a cell wall. The organelles of the organism and its cytoplasm are
therefore bound by a plasma membrane that allows for easier movement.
Observation of Euglena under more powerful electron microscopes have revealed
the presence of an ornamented pellicle under the plasma membrane. The presence
of this thin protein layer protects the their cell membrane and also
helps in maintaining their shape. Moreover, because of their flexible nature,
they also facilitate movement.
* The pellicle under the membrane is composed of
a protein layer that is supported by microtubule structures. These tubules are
arranged in strips spiraling around the cell. As they slide over each other,
these strips enhance flexibility and contractility of the membrane making it
possible for the organism to squeeze and pass through tiny spaces.
Chlorophyll and Eyespot
A closer observation of the organism will reveal
a reddish spot at the anterior part of the Euglena. This is an important
organelle that contains carotenoid granules that allows the organism to sense
and move towards sunlight.
The eyespot also helps filter the wavelength of
light that reaches the paraflagellar body, which is the light detecting
structure that lies at the base of the flagellum. In response to this, Euglena
moves towards the source for photosynthesis. This bodily movement of the
organism is commonly known as positive phototaxis.
In addition to the red eyespot, students will
also notice dark (greenish) spots throughout the body of the organism. Some of
these spots are chloroplasts that contain chlorophyll that produces the green
hue and responsible for photosynthesis. This is typically referred to as
chlorophyll A. Some organisms have both chlorophyll A and B. For such,
chlorophyll B produces a bluish green color and enhance the absorption of light
required for photosynthesis.
Chloroplast in the organism trap light
(sunlight) that is used to manufacture food through photosynthesis.
process can be summarized as follows:
Carbon dioxide + Water (in the presence of sunlight)
glucose and oxygen
This makes them autotrophic organisms given
that they are capable of making their own food when there is sunlight.
Although they are capable of making their own
food, they are also heterotrophic, which means that they also consume food.
Food consumption by heterotrophs takes place through phagocytosis.
organism engulfs the food particle in a vacuole to be digested. In the vacuole,
enzymes are released to digest the food particle. Euglena also has a
contractile vacuole that helps collect and remove excess fluids from the cell.
This prevents the cell from taking in too much water that can cause the cell to
Euglena are neither plants nor animals despite
the fact that they have characteristics of both. Given that they cannot be
groups under either the plant or the animal kingdom, Euglena, like many other
similar single celled organisms are classified under the Kingdom Protista.
Classification is as follows:
- Order - Euglenales
- Family - Euglenaceae
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G.F. Leedale (1964) Pellicle structure in
Euglena , British Phycological Bulletin,