They have a contractile vacuole. These contractile vacuoles helps in osmoregulation. Eulgenoids have a haploid nucleus and chloroplast. Flagellated Euglenoids locomote with the help of flagella. But non-flagellated Euglenoids are also motile. These non-flagellated euglenoids locomote by wriggling movement which is also called as Euglenoid movement.
Wriggling movement is due to wave motion of the pellicle. Also reproduce by cyst formation during unfavourable conditions. Scientists speculate that the chloroplasts within these cells were acquired as a result of endosymbiotic relationships with green algae. Since other Euglena do not have chloroplasts and the ones that do obtained them through endosymbiosis, some scientists contend that they should be placed taxonomically in the phylum Euglenozoa.
In addition to photosynthetic euglenids, another major group of non-photosynthetic Euglena known as kinetoplastids are included in the Euglenozoa phylum.
These organisms are parasites that can cause serious blood and tissue diseases in humans, such as African sleeping sickness and leishmaniasis disfiguring skin infection. Both of these diseases are transmitted to humans by biting flies. Common features of photosynthetic Euglena cell anatomy include a nucleus, contractile vacuole, mitochondria, Golgi apparatus, endoplasmic reticulum, and typically two flagella one short and one long. Unique characteristics of these cells include a flexible outer membrane called a pellicle that supports the plasma membrane.
Some euglenoids also have an eyespot and a photoreceptor, which aid in the detection of light. Structures found in a typical photosynthetic Euglena cell include:. Some species of Euglena possess organelles that can be found in both plant and animal cells. Euglena viridis and Euglena gracilis are examples of Euglena that contain chloroplasts as do plants. They also have flagella and do not have a cell wall , which are typical characteristics of animal cells.
Most species of Euglena have no chloroplasts and must ingest food by phagocytosis. These organisms engulf and feed on other unicellular organisms in their surroundings such as bacteria and algae. Most Euglena have a life cycle consisting of a free-swimming stage and a non-motile stage.
In the free-swimming stage, Euglena reproduce rapidly by a type of asexual reproduction method known as binary fission. The euglenoid cell reproduces its organelles by mitosis and then splits longitudinally into two daughter cells.
When environmental conditions become unfavorable and too difficult for Euglena to survive, they can enclose themselves within a thick-walled protective cyst. Protective cyst formation is characteristic of the non-motile stage. In unfavorable conditions, some euglenids can also form reproductive cysts in what is known as the palmelloid stage of their life cycle.
In the palmelloid stage, Euglena gather together discarding their flagella and become enveloped in a gelatinous, gummy substance. Individual euglenids form reproductive cysts in which binary fission occurs producing many 32 or more daughter cells. How to cite. Predominately inhabitants of the freshwater environment, these unicellular flagellates are cylindrical, ovoid to fusiform, microscopic plants of eukaryotic organization possessing a true nucleus and other membrane-bound organelles with usually two flagella for locomotion, an undifferentiated cell wall, and chloroplasts; colorless varieties are known Fig.
This is a preview of subscription content, log in to check access. Beutow, D. The Biology of Euglena. New York: Academic Press, p. Google Scholar. Bold, H. The Plant Kingdom. Englewood Cliffs, N.
Chapman, V. The Algae. London: Macmillan, p. Fritsch, F.
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