Paramecium

Structure of Paramecium:-
Kingdom :- Animalia
Phylum :- Protozoa
class :- Ciliata
Genus :- Paramecium
Species :- caudatum

Habit and Habitat
Paramecium is an unicellular, miscroscopic Eukaryotic protozoan.Mostly found in stagnant fresh water like ponds, ditches, well etc rich in organic food material because bacteria is the chief food of paramecium. In paramecium, the nutrition is holozoic.Digestion is intracellular. Respiration and Excretion occurs through general body surface. It reproduces asexually by transverse binary fission and sexually by conjugation.
Structure of Paramecium
Paramecium majorly is divided into three main parts which of them are as follows:-
1. External Structure
2. Internal Structure
3. Feeding Structure

1. External Structure
a:) Pellicle
Pellicle is a thin elastic, porous, limiting membrane of the paramecium made up of gelatin protein. It provides definite shape to the paramecium as well as protects the internal organelles from mechanical energy.
b:) Tricocyst
Tricocyst is a spindle sac like structure abundantly found in Ectoplasm. It lies perpendicular to pellicle and alternating with cilium. The sac contain toxin that helps in offence and defence.Tricocyst helps in Anchoring during conjugation.When the organism is excited or disturbed, it immediately ejects out it’s needle to release toxic chemicals that prevents it from enemy as well as helps in trapping the food.
c:) Cilia
Cilia origins from basal granules that lies in Ectoplasm. Cilia are uniformly distributed throught the body except towards posterior and where it is larger and longer.This group of cilia is called caudal tuft. Caudal tuft helps in Anchoring to substratum as well as regulate direction of movement. Cilia are main locomatory organ as well as it helps in tranporting food materials from different parts of the Ectoplasm of the body to the oral group.
2. Internal Structure
a:) Nucleus
In paramecium, Nucleus shows Nuclear dimorphism i.e. Macro Nucleus and Micro Nucleus is large kidney or bean shaped and it is mainly responsible for metabolic activities of paramecium whereas the Micro Nucleus is small spherical shaped which lies near the concavity of Macro Nucleus and is responsible for regulating sexual reproduction i.e. conjugation
b:) Contractile Vacoule
It is two in number each in anterior and posterior end. Indivisual contractile vacoule are provided with radiating or feeder canal that collect excess salt and water from different part of the cytoplasm. The main vacoule expells excess salts and water outside the body through pellicular pores. The contractile vacoules work in systolic and diastolic pattern. It’s main function is to regulate osmoregulation and partial excretion.
3. Feeding Structure of Paramecium
A shallow depression on the ventral surface through which ingestion occurs is called as oral groove. Oral groove leads to small ‘V’ shaped vestibule which further opens to small cytosome or cell mouth. These structures forms oral cavity.
i.e. Oral Cavity = Oral Groove + Vestibule
Cytosome further opens to long tubular ‘S’ shaped cytopharyx. On the posteriour end of cytopharynx, the food vacoules are formed. A the school vacoules separates from cytopharynx, the food vacoules moves in clockwise direction by streaming movement of cytoplasm i.e. cyclosis. Cyclosis helps in Digestion, Assimilation, and Egestion. The undigested food material are thrown out of paramecium body by temporory opening on ventral surface i.e. Cytopyge or Cell Anus