Paramecium Cell Definition, Characteristics, Classification, Movement, Diagram.

Paramecium is a single-celled, microscopic, free-living, and eukaryotic organism.

Written by SouravBio · 9 minutes read >

In this article, we will discuss paramecium definition, kingdom, characters, movement, classes, shape, size, habitat, etc.

Paramecium Scientific classification

Paramecium is divided into this following phylum and subphylum;

Domain:Eukaryota
Clade: SAR
Infrakingdom: Alveolata
Phylum: Ciliophora
Class:Oligohymenophorea
Order:Peniculida
Family: Parameciidae
Genus: Paramecium
Paramecium Classification

Paramecium Definition

Paramecium is a single-celled, microscopic, free-living, and eukaryotic organism. Paramecium cells are considered as the representative of the ciliate group and come under phylum Ciliophora. 

In the late 17th century, Antonie van Leeuwenhoek first described Paramecium. In 1752, English microscopist John Hill first coined the term “Paramecium”.

There are different paramecium species such as Paramecium aurelia, Paramecium polycarum, Paramecium woodruffi.

Paramecium Habitat

Paramecium is a free-living organism. They are usually found in stagnant water of pools, lakes, ditches, ponds, freshwater, and slow-flowing water which contains decaying organic matter.

Paramecium Size

The size of paramecium is varies from species to species;

  • Paramecium aurelia is 120-180 um long.
  • Paramecium bursaria is 180-300 um long.
  • Paramecium calkinsi is100-150 by 50 um long.
  • Paramecium caudatum is 180-300 um long.
  • Paramecium jenningsi is 115-218 um long.
  • Paramecium multimicronucleatum is  200-330 um long. It is considered as the largest species.
  • Paramecium polycaryum is 70-110 um long.
  • Paramecium putrinum is 80-150 um long.
  • Paramecium trichium is 50-105 (80-90) um long.
  • Paramecium woodruffi is 150-210 um long.

Paramecium Species

Paramecium biaureliaParamecium biaurelia
Paramecium primaureliaParamecium tetraurelia
Paramecium sonneborniParamecium quadecaurelia
Paramecium tredecaureliaParamecium dodecaurelia
Paramecium undecaureliaParamecium decaurelia
Paramecium novaureliaParamecium pentaurelia
Paramecium sexaureliaParamecium septaurelia
Paramecium octaureliaParamecium triaurelia
Paramecium bursariaParamecium buetschlii
Paramecium multimicronucleatumParamecium woodruffi
Paramecium schewiakoffiParamecium putrinum
Paramecium polycaryumParamecium nephridiatum
Paramecium jenningsiParamecium grohmannae
Paramecium duboscquiParamecium chlorelligerum
Paramecium caudatumParamecium calkinsi
Paramecium Species

Paramecium Characteristics

  • Paramecium is an unicellular organism.
  • Paramecium is a eukaryotic cell.
  • Paramecium kingdom is Protista and the genus is ciliate protozoa.
  • The phylum of Paramecium is Ciliophora.
  • The paramecium size ranges from 50 to 300um.
  • They contain cilia (hair-like filaments) all over the body surface which help them in locomotion.
  • The oral groove Paramecium cell contains oral cilia which drag the food to its oral cavity.
  • The shape of Paramecium resembles the sole of a shoe or slipper, that’s why it is also known as slipper animalcule.
  • Paramecium cells contain different complex organelles. Each of them performs a specific function which makes its survival possible.
  • They contain a complex reproductive activity.
  • P. bursaria and P. chlorelligerum show symbiotic relationship with green alage.

Paramecium Structure With Labeled Diagram

(i) Paramecium Shape and Size

  • The size ranges from 170 to 290um or up to 300 to 350um.
  • They are visible with the naked eye and it contains an elongated slipper-like shape, that’s why they are also known as the slipper animalcule.
  • The posterior end of the Paramecium cell is pointed, thick whereas the anterior part is broad and blunt.
  • The middle part is considered the widest part of the body.
  • It has an asymmetrical body.
  • It contains a convex aboral or dorsal body surface. 

(ii) Pellicle

  • Paramecium contains a flexible, thin and firm membrane known as Pellicle. The whole body is surrounded by this Pellicle.
  • The Pellicle is elastic in nature and supports the cell membrane.
  • The Pellicle is composed of a gelatinous substance.

(iii)  Cilia

  • Cilia are small hair-like projections which cover the whole body.
  • They are arranged in columns of uniform length throughout the animal’s body.
  • The diameter of cilia is about  0.2um.
  • At the posterior end, it contains a few longer cilia which form a caudal tuft of cilia, that is why they are called caudate.
  • The structure is similar to the flagella, it has a sheath which is made of protoplast or plasma membrane with longitudinal nine fibrils in the form of a ring.
  • The outer fibrils are thicker as compared to inner ones.
  • Cilia help in locomotion and intake of food through the oral cavity.

(iii) Cytostome

Cytostome has different components such as;

(a) Oral groove

  • The ventrio-lateral part of the body contains a large oblique shallow depression known as peristome or an oral groove.
  • It provides an asymmetrical appearance to the Paramecium cell.
  • The Oral groove is extended and formed a vestibule which looks like a short conical funnel. Then the vestibule is extended  into the cytostome through the cytopharynx and then the esophagus leads to the food vacuole.

(b) Cytopyge

  • It is also known as cytoproct which is located at the ventral surface, just behind the cytostome.
  • It eliminates undigested foods.

(c) Cytoplasm

  • It is made of jelly-like substance.
  • It is differentiated into the ectoplasm, which is a narrow peripheral layer.

(d) Ectoplasm

  • It develops a  thin, dense, and clear outer layer.
  • This layer contains cilia, trichocysts, and fibrillar structures.

(e) Endoplasm

  • The Endoplasm contains different granules, inclusions, and structures such as vacuoles, mitochondria, nuclei, food vacuole, contractile vacuole etc.

(f) Trichocysts

  • Trichocysts are small spindle-like bodies which remain Embedded within the cytoplasm.
  • It contains a dense refractive fluid with swelled substances.
  • They are perpendicular to the ectoplasm.

(iv) Nucleus

The Nucleus is made of two important components such as macronucleus and a micronucleus.

(a) Macro Nucleus

  • It has a kidney or ellipsoidal shape which is densely packed within the DNA (chromatin granules).
  • Macro Nucleus is also called a vegetative nucleus because it controls all the vegetative functions.

(b) Micro Nucleus

  • These are small in size and spherical in shape; located close to the macronucleus.
  • The number of Micro Nucleus varies based on the species.
  • Caudatum Lacks nucleus.

(v) Vacuole

It is made of two vacuoles such as contractile vacuole and food vacuole.

(a) Contractile vacuole

  • The Paramecium cell contains two Contractile vacuoles that are located close to the dorsal side; filled with fluids.
  • They are also known as temporary organs because they can disappear periodically.
  • They are connected with more than 5 radical canals, which are made of a long ampulla, a terminal part, and a short injector canal. This short injector canal is directly opened within the contractile vacuole.
  • These canals transfer the liquid from the whole body to the contractile vacuole, as a result, the size of the contractile vacuole is increased. Then the liquid is released from the body through a permanent pore.
  • contractile vacuole also helps in osmoregulation, excretion, and respiration.

(b) Food vacuole

  • They are non-contractile vacuoles.
  • They are roughly spherical in shape.
  • The size, digest food particles, enzymes, fluid, and bacterial content of food vacuole varies based on the species.
  • They remain associated with digestive granules.

Paramecium Labeled Diagram

Paramecium Cell Definition, Characteristics, Classification, Movement, Diagram.
Paramecium Cell labeled Diagram | Image Source: Wiki | Image Author: Deuterostome

Paramecium Movement

The most asked question is “how paramecium move?” Basically, they use cilia for their movement.

  • The cilia is located at the surface area of the cell. They are arranged in tightly spaced rows.
  • The constant motion of cilia helps them in movement. The speed of the movement is 4 times of its body’s length per second.
  • They rotate the cilia around its own axis to move forward, it also helps them to push the food into the gullet.
  • Paramecium can move in reverse by rotating the cilia in reverse direction.

Paramecium Feeding

Paramecium mainly eats bacteria, algae, and yeasts. Now the question is “how paramecium eat?” basically Paramecium follow these following steps to eat their food;

  • To obtain their food, they first trap the prey organisms with the movements of cilia and then take it through their oral groove, and then into the cell. 
  • Then the foods come to the buccal cavity or gullet from the cilia-lined oral groove.
  • Then the food particles move through the cytostome, or cell mouth, into the interior part of the cell. 
  • After that the foods are stored into the food vacuoles, which are periodically closed off and released into the cytoplasm. After that they started to circulate through the cell body.
  • The cyclosis or cytoplasmic streaming helps in the circulation of food vacuoles within the cell.
  • As the food enters into the food vacuoles different digestive enzymes and hydrochloric acids are released within the food vacuoles. As a result the vacuoles become  more acidic, the pH drops from 7 to 3.
  • After that the vacuole starts to shrink and the digestive nutrients enter into the cell cytoplasm.
  • When the vacluoles comes to the anal pore they ruptures and release the waste at the outside of the cell.

Paramecium Reproduction

  • They contain dual nuclear apparatus as like other ciliates. Their nucleus is made of one or more diploid micronuclei and a polyploid macronucleus.
  • The micronucleus helps in genetic stability and also confirms that the desirable genes are passed from one generation to the next. The micronucleus is also known as the generative, or germline nucleus
  • The macronucleus helps in non-reproductive cell functions such as helps in expression of genes which are needed for daily functioning of the cell.
  • They reproduce asexually by using binary fission, it may occur spontaneously. During the reproduction, micronuclei undergo mitosis whereas the macronuclei divide by amitosis.
  • After the end of transverse division of the cell, each new cell will contain two copies of macronuclei and micronuclei.
  • They may also follow the autogamy or self-fertilization under certain conditions or it may follow conjugation.
  • In Paramecium conjugation, a Paramecium cell temporarily fuses with mating types and then exchanges their genetic materials. It is a sexual phenomenon.
  • The meiotic division takes place in micronuclei during the conjugation as a result of this meiotic division haploid gametes are produced and they pass on from cell to cell.
  • After that the newly formed gametes are fused and develop a new diploid micronuclei while the old macronuclei are destroyed.
  • Under unfavorable conditions or shortage of food, the paramecium follows the conjugation or Autogamy for reproduction.

Paramecium binary fission

Video Author: Deuterostome

Paramecium in conjugation

Video Author: Antonio Guillén

Paramecium Under Microscope

To observe Paramecium Under Microscope, take a jar with mud, grass and pond water. Then seal the lid and keep where it can get a lot of sunlight.

After a few days, place a drop of water from the jar on a slide and cover it with a cover slip. Then observe it under the microscope, starting at 40x.  

Paramecium Cell Under Microscope
Paramecium Cell Under Microscope | Image Source: www.mcgill.ca | Image Author: AdaMcVean

Paramecium Aging

During the mitotic cell division in the asexual reproduction of paramecium the clonal aging occurs which leads to the gradual loss of energy.

In some paramecium species such as a well-studied specie Paramecium tetraurelia has been known that the cell expires right after 200 fissions if the cell relies only on the asexual line of cloning instead of conjugation and autogamy.

During the clonal aging, the DNA damage occurs within the macronucleus which results in aging in P. tetraurelia. According to the DNA damage theory of aging the aging process in single-celled protists is the same as that of the multicellular eukaryotes.

Paramecium Genome

The sequencing of P. tetraurelia provides strong evidence for the three whole-genome duplications.

The UAA and UAG codon in Stylonychia and Paramecium are reassigned as sense codons whereas UGA as a stop codon.

Paramecium Example

(i) Paramecium Caudatum

  • It is an unicellular protist of phylum Ciliophora.
  • Their size can be 0.33 mm in length.
  • They contain small hair-like structures all over the surface area known as cilia which help them in locomotion and feeding.
  • They are spindle-shaped, the front portion is rounded and tapering at the posterior to a blunt point.
  • They contain 2 contractile vacuoles.

Paramecium Caudatum Reproduction

Paramecium Caudatum reproduces through the binary fission which is an asexual method. Under unfavorable conditions they reproduce by self-fertilization (autogamy) or conjugation.

Paramecium Caudatum Under Microscope

Here is the picture of Paramecium Caudatum Under Microscope

Image Sourec: Wiki | Author: Deuterostome

Paramecium Caudatum Under Microscope video:

Author: Alexander Klepnev

(ii) Paramecium aurelia

  • They can be found in freshwater environments, and are especially in scums.
  • Acidic conditions attract them.
  • They feed on bacteria and dead organic matter.
  • They contain hair-like cilia all over the surface.
  • They can reproduce by sexually, asexually, or by the process of endomixis.

Other examples of Paramecium are Paramecium tetraurelia, Paramecium bursaria.

Video: Paramecium bursaria | Author: Deuterostome

Paramecium putrinum | Author: Deuterostome

Paramecium Cell Examples
Paramecium Cell Examples

FAQ on Paramecium

1. Are paramecium autotrophic or heterotrophic?

Paramecium are heterotrophic, they feed on other microorganisms such as bacteria, algae, and yeasts.

2. Are paramecium unicellular or multicellular?

Paramecium are single celled or unicellular protists.

3. How paramecium move?

Paramecium moves by using their cilia. During their movement they rotate their cilia.

Further Reading

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Writer and Founder of Microbiologynote.com. I am from India and my main purpose is to provide you a strong understanding of Microbiology. Microbiologynote.com shares notes related to different branches of microbiology.

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