Paramecium

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An Overview of Paramecium

Paramecium is a unicellular, eukaryotic organism belonging from kingdom Protista. Its size varies between 50 to 300um, depending on the species. There is a total of 10 species of Paramecium; Aurelia and Caudatum are two of them. 

These ciliate protozoans 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. 


Characteristics of Paramecium

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Fig1: Paramecium diagram

Paramecia are visible with naked eyes. Also, because of their slipper-like structure, they are known as slipper animalcule. Following are the components of it.

  • Cilia are the hair-like fibre 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 :

  1. Oral Groove- This large shallow oblique depression is on the ventrolateral side of the Paramecium, giving it an asymmetrical shape.

  2. Cytopyge- This part helps in eliminating all the undigested food.

  3. Cytoplasm- It consists of a jelly-like material that exists within ectoplasm.

  4. Ectoplasm- A thin, clear and dense layer is called ectoplasm that includes cilia, fibrillar structures and trichocysts. 

  5. Endoplasm- This particular part includes different granules like mitochondria, food vacuoles, nuclei, etc. 

  6. 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 Classification

Class

Ciliates 

Phylum

Protozoa 

Subphylum

Ciliophora 

Genus

Paramecium 

Order

Peniculida 

Family 

Parameciidae 

Paramecium kingdom is Protista, and it is a part of the aquatic ecosystem. 

A few Species of Paramecia are 

  • Paramecium Caudatum.

  • Aurelia.

  • Trichium. 

  • Woodruffi. 

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 buccal cavity, and food enter the body through it. 

  • Vestibule ciliary tract directs the food towards buccal cavity. 

  • Smaller particle of food reaches cytopharynx through Cytosome. 

  • The food particles then take form of food vacuoles and collect at the lower portion of cytopharynx. 

  • Every food vacuole consisting of food material undergoes circulation with cyclosis. 

  • Afterwards, 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 then absorbed by cytoplasm and aids in growth and development of the organism.  

  • In the end, the indigested food leaves the body through cytoproct or anal spot. 


 Reproduction of Paramecium

Like other ciliates, Paramecium contains dual nuclear system. These are diploid micronuclei and polypoid macronucleus. Micronuclei help in maintaining genetic stability. On the other hand, macronucleus aids in continuing 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 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 migratory male pronucleus while the larger one is stationary female pronucleus. 

  • The male pronucleus travels through protoplasmic bridge and fuses with the female one to form 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-fertilise under certain situations. Autogamy and conjugation usually occur when there is a lack of nutrition, and water temperature is lower than usual. 

FAQ (Frequently Asked Questions)

1. How does Paramecium Reproduce?

Ans. Paramecium reproduction happens both sexually and asexually. However, asexual reproduction through conjugation is most common. 

2. What is the mode of Locomotion in Paramecium?

Ans. The mode of locomotion in paramecium is cilia. 

3. How does Paramecium get rid of Excess water?

Ans. 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 cell membrane.