Euglena – Overview
A length of 40-60 microns and about 14-20 microns wide (at its thickest body part), Euglena Viridis is a microbe depicting both animal and plant features. These single-celled flagellates are seen across the globe and are found inhabiting brackish and freshwater richly supplied with organic matter and can also be seen in moist soil. These photosynthetic protists are usually categorised in the phylum Euglenophyta or phylum Euglenozoa.
Appearing spindle-shaped and elongated, their anterior end is blunt while the mid-section is wider in comparison, tapering down towards the posterior terminal. The body is covered by a flexible, fine, strong and tough pellicle or cuticular periplast that is seen under the plasma membrane.
The pellicle comprises fibrous elastic proteins and preserves the definite structure of the body. Still, it shows flexibility to allow provisional changes in the shape of the body. Such changes are referred to as the euglenoid movements.
A funnel-shaped cytostome is present at the anterior end, slightly to one side of the centre. The cytostome or the cell mouth directs to a small tubular cytopharynx that in turn unites with a large spherical vesicle – the flagellar sac. The cytopharynx or cytostome are not deployed in ingestion of food but as a canal from where fluid escapes from the reservoir.
The whip-like, long and single flagellum projects from the cytostome through the cytopharynx. The length of the flagellum varies in different species of Euglena; however, in Euglena Viridis, these structures are as long as the length of the body.
These emerge by two roots from the reservoir’s base from the side opposite to that of the contractile vacuole. Each of the roots emerges from the blepharoplast or the basal granule that is planted in the anterior section of the cytoplasm.
The flagella comprise an inner axial filament and an outer contractile protoplasmic sheath. The distal part of the flagella has many small fibres – mastigonemes that emerge from one side of the sheath. As a result, the flagellum is a stichonematic type.
Euglena Viridis – Locomotion
Locomotion in Euglena viridis involves two modes:
- Euglenoid movement
- Flagellar movement
At times, Euglena exhibits an unusual and slow-paced movement. This peristaltic pattern of contraction and expansion moves over the complete body from the anterior to the posterior terminal, and hence the animal inches forward. First, at the anterior terminal, the body becomes wider and shorter, then in the middle and later on at the posterior terminal. The movement is referred to as euglenoid movement, by which restricted and slow movement takes place.
The euglenoid movements are enforced by the contractions of the myonemes seen in the cytoplasm or contraction of the cytoplasm.
Scientists have observed that the flagellum experiences a sequence of lateral movements, and in this process, pressure is exerted on the water perpendicular to its surface. The pressure generates two forces – one that acts perpendicular to the main body axis and one that acts parallelly. The parallel force drives the animal in the forward direction while the force that acts perpendicular rotates the animal on its own axis.
A series of spiral waves pass along the flagellum, causing its body to rotate one time in one second. As a result, in its movement, it forms a spiral path through a straight line and advances forward. The pace of movement is 3 mm every minute.
This was a brief on the Euglenoid movement. The next suggested topic that would interest you is the Krebs cycle. Subscribe to BYJU’S YouTube Channel to learn in detail about it and for related content.