TOPIC-I : TYPE STUDY . PARAMOECIUM

TOPIC-I : TYPE STUDY

. PARAMOECIUM

General characters

Shape, size and colour: Paramecium caudatum is called "animal ". Its anterior end is bluntly rounded while the posterior end is conical and pointed.
Pellicle: It is a thin flexible and living membrane which maintains its shape.
cytoplasm is differentiated into outer ecotoplasm and inner endoplasm.
Cilia: Numerous cilia are distributed over the body surface. The cilia of the extreme posterior end are longer and form a bunch called caudal tuft.

Cilia are for locomotion , food capture and are also tactile in function (respond to touch).
Trichocysts: These are fusiform bodies present  just below the pellicular.

Oral grove: It consists of a shallow and wide peristome and  funnel-like vestibule, buccal cavity which opens through a cytostome

A temporary opening is called cytopyge is present a little behind the cytostome. Undigested food is passed through cytopyge.

Nuclei: Paramecium caudatum contains a two nuclies and according to their size  large macronucleus (= meganucleus) and smaller micronucleus.

Contractile Vacuoles and Radial Canals: Paramecium contains two contractile vacuoles which have fixed position. One contractile vacuole is present near the anterior and while another contractile vacuole is found towards posterior end of the body.

Each contractile vacuole is surrounded by 8 to 10 radial canals

The contractile vacuoles and radial canals are for osmoregulation.
Food Vacuoles : The food vacuoles are meant for intracellular digestion.

i)  External Morphology

                                                   Paramecium caudatum

1.      Paramecium is a free-living ciliate which is found in fresh water ponds, pools, ditches, rice fields and slow streams having decaying matter.

2.      It is abundant in water which has plenty of bacteria.

3.      Nutrition is holozoic.

4.      Bacteria are its chief food. Paramecium is a surface feeder.

5.      It swims actively with the help of cilia.

6.      Both asexual (e.g., transverse binary fission) and sexual reproduction (e.g., conjugation) are found in paramecium.

 

 

ii)   BINNARY FISSION IN PARAMOECIUM 

                                 Transverse Binary Fission in Paramecium

 

1.            Paramecium reproduces asexually by transverse Binary fission

2.            The, cytoplasm, micronucleus and macronucleus undergoes transverse division.

3.            Micronucleus divides mitotically.

4.            Macronucleus divides amitotically get elongated and divides into two.

5.            On pellicle transverse groove or  constriction is developed at the middle which divides the body of paramecium into two halves.

6.            Each half of the cell is having a daughter nucleus and a contractile vacuole.

7.            New oral grove, New contractile are developed

8.            Finally the separation of two daughter cells takes place, thus two individuals are formed, which are called daughter paramecium. 

iii)  CONJUGATION IN PARAMOECIUM 

1. •      Sexual reproduction is takes place by conjugation.
2. •      During unfavorable condition 2 conjugating individual come together by their oral side .
3. •      Pellicle at the point of contact get  degenerate  forming Cytoplasmic  bridge
4. •      Macronucleus  breaks into fragment and get absorbed in to cytoplasm.
5. •      Remaining micronucleus divides two time to produce 4 nuclei.
6. •      Out 4 nuclei 3 get degenerate
7. •      Remaining nucleus divides unequally in to two
8. •      Male pro-nucleus  pass through cytoplasmuic bridge and fuse with Female pro-nucleus of other paramecium
9. •      After zygote formation conjugating individuals get separate and here they are called as Exconjugants
10. •      Remaining nucleus divides 3 times to produce  8 nuclei.
11. •      Out of 8 nuclei 4 become micronucleus and 4 become micronucleus .
12. •      Paramecium and micronucleus divides 2 time to produce 4 daughter paramecia.
13. •      At the end of process of conjugation 8 daughter paramecia are develops

Author 

Dr. Vidhin Kamble

Department of Zoology

Sangola College, Sangola Dist. Solapur(M. S. ) 

India