Paramecium is a unicellular, eukaryotic organism belonging to the kingdom Protista. Its size varies between 50 to 300um, depending on the species. There are a total of 10 species of Paramecium; Aurelia and Caudatum are two of them.
These ciliate protozoa are found mainly in freshwater as well as brackish and marine water. Also, Paramecium reproduction is complex and occurs through several mechanisms. They are studied for several biological processes because of their wide availability.
This article will focus on what is Paramecium and its allied topics
A Detailed Study on Paramecium
In previous articles on biological taxonomic classification, we have learned about the kingdom Protista after the kingdom monera. Like the organisms in kingdom monera, the organisms in Kingdom Protista are also unicellular. The body of such an organism consists of only one cell. These organisms are also eukaryotic in nature. These organisms don't have many cells like other higher developed organisms that we see around us.
Among the different types of unicellular eukaryotic elongate or foot-shaped organisms, they are called Paramecium. It grows up to 50 to 300 micrometers and can be properly observed under a microscope. In fact, in the 17th century microscopists got to know for the first time about ciliates through discovering Paramecium. The body of Paramecium is covered by the pellicle which is a rigid but elastic structure. They contain the cell membrane inside this capsule. With the help of locomotive organs, it propels itself in water. It is heterotrophic in nature and feeds on various microorganisms such as bacteria, algae, and yeast for food. The oral groove is also lined with cilia that help in passing the food into the buccal cavity and then to food vacuoles. The digestion takes place in vacuoles and the nutrients get absorbed into the cytoplasm. The habitat of these protozoans can be any water body containing freshwater, brackish water or even marine water. This organism actively performs osmoregulation for various functions such as balancing the water and fluid balance inside the cells. The organs like contractile vacuoles perform this activity in the Paramecium. Because of their wide availability and easy observation under a microscope, these organisms are widely used for studying single-celled organisms in laboratories. Hence, they are often rightly referred to by some as the white rat of the Ciliophora phylum.
Characteristics of Paramecium
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Paramecia are visible with naked eyes. Also, because of their slipper-like structure, they are known as slipper animalcules. Following are the components of it.
Cilia are the hair-like fiber that covers the whole body. It primarily helps in locomotion and gathering food.
A pellicle is a flexible, firm, and thin membrane that protects the entire body. It is elastic and consists of gelatinous material.
Cytostome consists of several parts, including :
Oral Groove- This large shallow oblique depression is on the ventrolateral side of the Paramecium, giving it an asymmetrical shape.
Cytopyge- This part helps in eliminating all the undigested food.
Cytoplasm- It consists of a jelly-like material that exists within the ectoplasm.
Ectoplasm- A thin, clear, and dense layer is called ectoplasm that includes cilia, fibrillar structures, and trichocysts.
Endoplasm- This particular part includes different granules like mitochondria, food vacuoles, nuclei, etc.
Trichocysts- It is contained within the cytoplasm and filled with refractive fluid.
Nucleus- Paramecium’s nucleus is further classified into two parts, micronucleus, and macronucleus. Paramecium reproduction typically transforms the nucleus. However, Caudatum does not contain any nucleus.
Vacuole- This organism has two types of vacuoles, food and contractile. While food vacuoles aid in food digestion, contractile ones help in excretion, respiration, and osmoregulation.
Paramecium kingdom is Protista, and it is a part of the aquatic ecosystem.
A few Species of Paramecia are
The following chart elucidates the origin of Paramecium and to the classes, it belongs to.
Feeding Mechanism of Paramecia
Apart from paramecium reproduction, its feeding mechanism is equally essential and elaborate. Paramecium consumes several kinds of food, including unicellular plants, bacteria, tiny insects, and plants. It intakes food through cilia.
Cytosome lies at the bottom of the buccal cavity, and food enters the body through it.
Vestibule ciliary tract directs the food towards the buccal cavity.
A smaller particle of food reaches the cytopharynx through Cytosome.
The food particles then take the form of food vacuoles and collect at the lower portion of the cytopharynx.
Every food vacuole consisting of food material undergoes circulation with cyclosis.
Afterward, the enzymes of protoplasm help digestion.
The vacuole content first turns acidic and then alkaline during digestion. The vital part of digestion takes place during the alkaline phase.
In this process, the proteins are transformed into amino acids. Similarly, carbohydrate turns into soluble sugar and glycogen.
The digested food is then absorbed by the cytoplasm and aids in the growth and development of the organism.
In the end, the indigested food leaves the body through a cytoproct or anal spots.
Reproduction of Paramecium
Like other ciliates, Paramecium contains a dual nuclear system. These are diploid micronuclei and polypoid macronucleus. Micronuclei help in maintaining genetic stability. On the other hand, the macronucleus aids in continuing the daily functioning of the cell.
Paramecium reproduction mainly happens asexually by binary fission. In this process, micronuclei undergo mitosis, and macronucleus divide by amitosis. Finally, each new cell contains a version of micronuclei and macronucleus. Binary fission may happen spontaneously.
It also reproduces sexually through conjugation. During this process, micronuclei undergo a meiotic division. Conjugation in Paramecium leads to haploid gamete formation. It further spreads from cell to cell. The process takes place in the following steps.
After coming in contact with each other, two paramecia unite through the sides of their oral grooves. In this process, they are called conjugants.
The macronucleus of each conjugant then disappears. Likewise, the micronuclei divide twice and create four haploid micronuclei.
Three micronuclei out of the four then disintegrate. The remaining one forms two daughter pronuclei. The smaller one of these is a migratory male pronucleus while the larger one is a stationary female pronucleus.
The male pronucleus travels through the protoplasmic bridge and fuses with the female one to form a zygote.
The zygote nucleus is diploid and called amphinucleus.
Once the zygote is formed, the nucleus divides and creates four daughter paramecia.
Conjugation assists in transferring genetic materials and rejuvenation.
Apart from that, paramecia are also capable of Autogamy. It means they can self-fertilize under certain situations. Autogamy and conjugation usually occur when there is a lack of nutrition, and water temperature is lower than usual.
All the unicellular organisms on earth are categorized into two groups known as Eukaryotic and Prokaryotic. The cell body of Prokaryotic organisms does not have well-defined cell organelles inside it. However, unlike prokaryotic organisms, the cell body of eukaryotic organisms contains well-defined organelles such as mitochondria Golgi apparatus, and others that are bound by a membrane. Eukaryotic unicellular organisms are very limited in number but all the multicellular organisms are Eukaryotic. These cells can perform both mitosis and meiosis for division.
2. What is cilium?
As the single-celled organisms also carry out all the functions essential for sustaining life such as ingestion, digestion, excretion, reproduction so they need to move or get transported from one place to another. However, multicellular organisms do not have special locomotive organs to do so. Hence, some unicellular organisms have developed a special structure in the cell they process to move in the fluid they live in. These parts of the cell are known as cilia and the organisms that contain such ciliates are known as ciliates.
3. Who coined the term Paramecium?
In the late 17th century, Antonie Van Leeuwenhoek was the scientist who pioneered the study of protozoology. A clear description of the Paramecium can be found in one of the letters of his contemporary Christian Huygens. Although, in 1703, the first illustration of Paramecium was published. Louis Joblot is another French Mathematician and microscopist who contributed significantly to the study of Paramecium. However, the name Paramecium was coined only in the year 1752. John Hill derived this term from the Greek word “parameters” which means oblong.
4. What are the different components of Paramecium?
Three broad divisions of the Paramecium body are Cytostome, Pellicle, and Cilia. The gelatinous membrane is the pellicle which is flexible and protects the organism. The hair-like structures all over it are the cilia as we studied earlier. Cytostome is the actual structure of the body that contains all the essential organs for the functioning of various bodily functions. It contains an oral groove for ingestion of food particles and cytopyge for exhausting the undigested particles. Cytoplasm, endoplasm, and ectoplasm are the remains filled inside the cell in layers. Trichocysts are the refractive fluid inside the cytoplasm.
5. In which book students can get a detailed study on Paramecium?
Paramecium is one of the widely studied unicellular organisms in biology. From the description of the chapters, different classifications of biological life forms on earth mention the Paramecium under the Phylum of protozoa. Though the detailed study with illustration and diagram is available in the Class 8 Science textbook of NCERT, the full description is available in Class 11 Biology chapters. Students can also learn about this interesting creature by themselves from the articles provided on Vedantu websites. To get access to all the study materials, they have to register themselves on the Vedantu website which is free for any student. Once registered, they can also download the articles in PDF format for later reference.
6. How does Paramecium Reproduce?
Paramecium reproduction happens both sexually and asexually. However, asexual reproduction through conjugation is most common.
7. What is the mode of Locomotion in Paramecium?
The mode of locomotion in paramecium is cilia.
8. How does Paramecium get rid of Excess water?
Paramecium absorbs water by osmosis. Then the excess water is stored into a contractile vacuole that swells. Lastly, the water is released by an opening of the cell membrane.