Internal Features of Paramecium

Internal features of Paramecium

It includes cytoplasm and associated organelles. Cytoplasm is differentiated into outer ectoplasm inner endoplasm.

Ectoplasm:

It is the highly viscous cytoplasm of the outer region. It is tough supportive and protective in nature. It contains trichocysts, infra ciliary system, and neuromotor system.

Trichocysts:

These are the small bottle-shaped bodies present in ectoplasm and arranged perpendicularly to the pellicle. Undischarged trichocysts are about 4µ long but after discharged it becomes 10 times longer i.e. 40µ. It consists of terminal cap, pointed spike and oval shaft with swelling substance.The swelling substance contains fibrous trichina protein which gets unfold while coming in contact with water. So, it is responsible to increase the length of trichocyst.

Functions:

These are organelles of defence, offence, and attachment.

Infraciliary system:

It includes the basal portion of cilia present in ectoplasm. It controls the movement of cilia.

Neuromotor system:

It is formed of a group of contractile fibrils distributed throughout the ectoplasm. It controls body contraction and also the ciliary movement.

Endoplasm:

It is transparent, less viscous cytoplasm of the inner region. It is secretive and nutritive in nature. It contains following organelles:

Nucleus:

Paramecium is called heterokaryotic i.e it contains two different types of the nucleus which are present in the middle part of the body. One is larger and kidney shaped called macronucleus or meganucleus. It controls the metabolism, vegetative growth, and development of the body. Another is smaller and spherical called micronucleus. It controls the reproductive activity of the body.

Contractile vacuoles:

There are two contractile vacuoles in paramecium. One is situated at the anterior end whereas another is situated at the posterior and slightly towards the dorsal surface. Each contractile vacuole is rounded water field body surrounded by the 6-10 radial canals which one extended far into the cytoplasm. They collect extra fluid and inject into the contractile vacuole. Because of this, vacuole is expanded. Contraction of vacuole discharged accumulated fluid outside the body through discharge canal that opens to the pellicle of dorsal surface. Posteriorvacuole contract faster than anterior as it is closer to the cytopharynx.

Function:

These are the organelles of osmoregulation and excretion.

Food vacuole:

These are the small rounded non- contractile body. They are found circulating within the cytoplasm. It is formed at the end of cytopharynx. It then separates from cytopharynx and undergoes circulation along with cyclosis. Formation of food vacuole is determined by the rate of feeding. They are the important organelles from intracellular digestion.

Cyclosis:

It is the streaming or cyclic movement of endoplasm. It is of great importance in circulation or distribution of digested food materials.

Feeding mechanism:

In general, paramecium comes t the water surface for feeding. It does not move while feeding. At first cilia of oral groove move very fast that creates water current. Because of this food material from surrounding medium are drawn towards the oral groove and collected in the vestibule. Larger food materials are rejected whereas smaller food materials are selected and ingested through cytostome.Ingested food materials are guided by cytopharynx. At the cytopharynx, food vacuole is formed.

It then separates and undergoes circulation indefinite path along with cyclosis. During circulation, complex food materials are digested into the simpler form. These digested food materials are distributed by means of cyclosis. Undigested food materials are passed outside the body through cytopyge.

Locomotion:

Locomotion is carried out in two ways which are described below:

By ciliary movement:

In Parameciumlocomotion mainly occurs by movement of cilia. It can move forward and backward. While moving forward, cilia strongly move from anterior to posterior. Similarly, for backward movement cilia strongly move from posterior to anterior. All the cilia do not move at a time. Cilia of transverse row move at the same time. It is called synchronous rhythm, whereas cilia of longitudinal row move one after another. It is called metachronous rhythm.

Metaboly:

It is the movement occurs due to the temporary change in body form through the contraction. This method is used while passing through the aperture smaller than its diameter.