As the peristaltic waves start forming and while it passes through the body, it causes the body to become shorter and wider first at the anterior end, and then in the middle, and later at the posterior end.
Due to this, the pellicular strips bend and move against one another. It is like one strip sliding in the groove of the other. The sliding of the pellicle strips in the grooves is lubricated by the secretion of underlying muciferous bodies. This resultedly creates elasticity and this elastic force tends the body to move forward. Thus, causing Euglenoid movement by means of the peristaltic movement activities of the pellicle.
Euglena has a stiff pellicle outside their cell membrane. This helps them keep their shape and structure intake while giving the body its flexibility and elasticity. And, some Euglena can be observed scrunching up and moving in an inchworm type fashion using the pellicle. This pellicle is a very important body part of the Euglena. This flagellum originates from blepharoplast which lies at the base of the reservoir in the anterior end of the body.
It is made up of an axial elastic filament or axoneme, covered by a protoplasmic sheath. This flagellum consists of 2 central fibres enclosed in an inner membranous sheath , and 9 peripheral fibres in the periphery of the flagellum. Each central fibres are single made of one fibre each and the peripheral fibres are paired made of two sub-fibres each. The 9 peripheral fibres bear a double-row arms each, all pointing in the same direction.
In the space between the peripheral and central fibres lie 9 secondary fibres. This whole structure of the flagellum is continuous from the base of the flagellum to the tip while being enveloped by the outer sheath which is continuous with the plasma membrane. The removal of excess of water from the body is known as osmoregulation. The elimination of excess of water is done by the contractile vacuole. The accessory contractile vacuoles collect excess of water from the surrounding cytoplasm and liberate their contents into the main contractile vacuole which gradually increases in size and finally bursts and forces the water into the reservoir.
From the reservoir water, escapes out by cytosome through the cytopharynx. Along with this, water soluble wastes are also thrown out of the body. Recently Chadefaud has pointed out that the contractile vacuole is surrounded by a specialised granular and excretory cytoplasm.
The contractile vacuole periodically attains its maximum size and collapses to discharge its contents into the reservoir i. Simultaneously, several small accessory vacuoles appear in the excretory cytoplasm. These vacuoles then fuse together to form a new large vacuole i. Euglena Viridis responds to a variety of stimuli and is very. It swims towards an ordinary light such as that from a window and avoids strong light.
If a culture of Euglena is examined, most of the animals will be found on the side towards the light. This is of distinct advantage to the animal, because light is necessary for the assimilation of carbon dioxide by means of its chlorophyll. Euglena will swim away from the direct rays of sun. Direct sunlight will kill the organism if allowed to act for a long time.
If a dish containing Euglenae is placed in the direct sunlight and then one half of it is shaded, the animals will avoid the shady part and also the direct sunlight and will remain in a small band between the two in the light best suited for them Fig. A swimming Euglena moves in a spiral manner rotating and gyrating around its own axis but it shows a shock reaction whenever the direction of light is changed. It has been found that the region in front of the eye spot is more sensitive to light than any other part of the body.
Euglena orientates itself parallel to rays of light whenever the paraflagellar body photoreceptor is shaded by the stigma or eyespot. The animal adjusts its position to the direction of light moving either towards or away from it. When the animal rotates, the stigma acts as a screen, the paraflagellar body is alternately exposed or shielded when light falls on it from the side. The animal adjusts itself until the paraflagellar body is continuously exposed, this happens when the source of light is either straight in front or behind.
Euglena gives avoiding reaction to mechanical, thermal and chemical stimuli on a trial and error pattern phabotaxis. When stimulated by a change, Euglena, in majority of cases, stops or moves backward, turns strongly towards the dorsal surface, but continues to revolve on its long axis. The posterior end then acts as a pivot, while the anterior end traces a circle of wide diameter in the water. The animal may swim forward in a new direction from any point in this circle.
This is avoiding reaction. Euglena Viridis reproduces asexually by longitudinal binary fission and multiple fission. Encystment also takes place.
Sexual reproduction does not occur, although a primitive form of it is reported in some species. During active periods, under favourable conditions of water, temperature and food availability, Euglena reproduces by longitudinal binary fission. The fission is always symmetrogenic, i. The nucleus divides by mitosis. The endosome elongates transversely and becomes constricted into two approximately equal parts. Nuclear division takes place within nuclear membrane. The organelles at the anterior end such as stigma, blepharoplasts, reservoir, cytopharynx and chromatophores and paramylum bodies are also duplicated.
The body begins to divide lengthwise, from the anterior end downwards to the posterior end resulting in the formation of two daughter individuals. The old flagellum is retained by one half, whereas a new flagellum is developed by the other, contractile vacuole and paraflagellar body do not divide but they disappear and are made again in the daughter individuals.
Multiple fission usually takes place in encysted condition. Sometimes during resting or inactive periods, encystment occurs in Euglena. The mass of cytoplasm and the nucleus inside the cyst undergo repeated mitotic divisions giving rise to 16 or 32 small daughter individuals.
On the return of favourable conditions, the cyst breaks and the daughter individuals escape out from the cyst. Each daughter individual develops the various organelles and starts the normal life.
Some workers considered the daughter individuals as the spores and this process as sporulation. Sometimes,usually under unfavourable conditions, large number of euglenae come close together, lose their flagella and become rounded.
They secrete gelatinous covering or mucilaginous matrix within which they remain embedded. This condition is called palmella stage which is often seen as green scum on the water surface of ponds. Individuals of palmella stage carry on metabolic activities and reproduce by binary fission. On the arrival of favourable conditions, the gelatinous covering swells by the absoprtion of water and the euglenae are released.
They regenerate their flagella and start normal active life. During unfavourable conditions such as drought, extreme cold or extreme hot, scarcity of food and oxygen Euglena undergoes encystment. First of all Euglena becomes inactive, loses its flagellum and secretes a cyst around it. The cyst is secreted by the muciferous bodies lying below the pellicle. The cyst is thick-walled, rounded and red in colour due to the presence of a pigment called haematochrome.
This cyst is of the protective type. During the encysted condition the periods of unfavourable conditions are successfully passed. During encystment, binary fission may occur one or more times, resulting in 2 to 32 small daughter euglenae within the cyst. On the return of favourable conditions, cyst wall breaks, the animals become active and emerge from the cyst to lead a normal free swimming life.
In fact, encystment occurs only to tide over the unfavourable conditions and during this condition dispersal of Euglena occurs to a wide area. Euglena Viridis shows many characters of plants such as chloroplasts with chlorophyll and holophytic nutrition but it is regarded as an, animal due to the following facts:. It is small, elongated, spindle-shaped measuring about 50 microns in length.
The chloroplasts are large, flat, plate-like and about ten in number. Each chloroplast bears a proteinaceous pyrenoid. Unlike Euglena viridis, its chloroplasts once lost in darkness cannot be regained. Its cytoplasm contains many paramylum bodies in association with the chloroplasts Fig.
It is large-sized measuring about 95 microns in length and 18 microns in width. Its body is elongated, spindle-shaped and posteriorly its body is drawn out as a tail. There are numerous, small, disc-like chloroplasts without pyrenoids. It is characterised by the paramylum bodies in its cytoplasm Fig. It is a typical euglenoid form and generally supposed to be the bleached form of Euglena gracilis.
Chloroplasts, stigma and paraflagellar body are not found. It exhibits nutrition by osmotrophy due to the absence of chloroplasts and its cytoplasm contains many paramylum bodies Fig. It is an euglenoid flagellate having somewhat stumpy body.
It is believed to feed holozoically by phagotrophy upon quite large microorganisms. Of its two flagella, one is locomotory and long, while the other is trailing and found attached to its body surface. The stigma and paraflagellar body are not found. Its cytoplasm contains food vacuoles and many small paramylum bodies. It is characterised by the presence of an accessory rod-like apparatus called trichites in its cytopharynx Fig. Top Menu BiologyDiscussion. Study Notes on Protozoa With Diagram. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes.
Euglena chloroplasts contain pyrenoids , a subcellular compartment inside chloroplasts. The photosynthesis produces paramylon , a starch-like carbohydrate. It serves as food storage and enables euglena to survive when light is not available. Although euglena is able to make its own food by photosynthesis, it can also consume food via phagocytosis , a process to engulf food particles in a vacuole.
A lysosome then fuses with a food vacuole, releasing enzymes to digest food. Euglena also has a contractile vacuole to collect and remove excess fluid from the cell. Without the contractile vacuoles, the euglena may burst. Euglena moves by whipping and turning its flagella in a way like a propeller.
The beating of the flagella created two motions. One is moving euglena forward transitional motion , and the other one is rotating the euglena body rotational motion. You can see how scientists study the euglena movement below. The cell completes one turn of the helix while undergoing a full rotation around the axis of the helix. Movie credit: Rossi M. Euglena is able to alter its shape and then return to its initial shape like an elastic rubber band, a process called euglenoid movement metaboly.
The movement is created by peristaltic waves. When peristaltic waves travel through the body, they trigger the body to become much shorter and wider first at the anterior end, and then in the middle, and finally at the posterior end.
Metaboly movement allows euglena to change its shape and return to its initial shape coupled with movement. Euglena reproduces asexually through binary fission on its longitudinal axis.
When environmental conditions become unfavorable and too difficult for them to survive, such as low moisture or scarce food supply, euglena forms a protective cyst around itself and becomes dormant. The euglena whips its flagella for directional movement, and it also rotates its body. In addition, green chloroplasts and red eyespot are present.
Magnification x. Interestingly, a Tokyo-based Euglena Company marketed Euglena -based food and beverage products in Now they shift their business model to biofuels using euglena.
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