Friday, 23 August 2013
Structure and Classification of Paramecium caudatum
Friday, 23 August 2013 by Unknown
Paramecium caudatum
Classification:
·
Phylum: Protozoa
·
Sub
Phylum: Ciliophora
·
Class: Ciliatea
·
Order: Hymenostomatida
·
Genus: Paramecium
·
Species: caudatum
It’s a free living organism having cosmopolitan (world-wide)
distribution. It lives in stagnant water of freshwater, ponds, pools, ditches,
lakes and slow flowing rich in decaying organic matter
2. Structure:
A: Shape & Size:
Paramecium cadatum is a unicellular and
microscopic protozoan. It measures 170 to 290 µm up to 300-350 µm.
It is visible to the naked eye. Its body has a constant elongated, slipper-like
shape, so it’s also called slipper
animalcule. Anterior part of the body is blunt and broad and posterior end
is thick, pointed and cone shaped, widest part is just below the middle. Body
is asymmetrical showing well defined oral
or ventral surface and convex dorsal
or aboral surface.
B:Pellicle:
The whole body is covered by thin, firm, flexible membrane called pellicle. Pellicle is made up of
gelatinous substance. It gives shape of the animal but is elastic to permit
contraction.
C:Cilia:
Body is covered by numerous, small hair-like projections called cilia,
arranged in longitudinal rows. The length of cilia is uniform throughout the
body ( a condition called holotrichous),
but there are a few longer cilia at the posterior end of body. These form caudal tuft of cilia (hence the name caudatum). Cilia have the same
structure as flagella, an outer protoplasmic sheath or plasma membrane with
nine double longitudinal fibrils, in a peripheral ring. Two central fibrils,
which are thinner than the outer fibrils. Each cilium arrives from a basal
granule. At the base the cilia has a diameter of 0.2 µm (2000 A ̊).
3. Cytostome:
3. Cytostome:
A: Oral groove:
On the ventro-lateral side is a large oblique, shallow depression called
oral groove or peristome which gives the animal asymmetrical appearance. The oral
groove lends into a short conical funnel shaped depression called vestibule. Vestibule leads to an oval
shaped opening called cytostome. It
is followed by a long opening called cytopharynx; which leads to the oesophagous - that leads to food vacuole.
B: Cytopyge:
The cytopyge or cytoproct lies on the ventral surface,
almost vertically behind the cytostome.
Undigested food particles are eliminated through the cytopyge.
C:Cytoplasm:
The cytoplasm is differentiated into a narrow peripheral layer of clear
and dense plasmegel, called ectoplasm and an inner large central
mass of granular and semifluid plasmasol
or endoplasm.
D:Ectoplasm:
It forms a firm, clear, thin
and dense outer layer. It contains the trichocysts,
cilia and fibrillar structures and is bound externally by a covering called pellicle.
E:Trichocysts:
Small spindle shape bags are embedded in the ectoplasm filled with a
refractive, dense fluid having swelling substance. At the outer end there is a
conical head on spike. Trichocysts
lie perpendicular to ectoplasm.
F:Endoplasm:
Endoplasm is the voluminous
part of the cytoplasm, contains many granules as well as other structures and
inclusions such as mitochondria,
vacuoles etc. other students includes nuclei, contractile vacuole, food
vacuole etc.
4. Nuclei:
A:Macro Nucleus:
It is a ellipsoidal or kidney like shaped nucleus. Densely packed with
chromatin granules (DNA). It is a vegetative nucleus, controls vegetative functions.
B:Micro Nucleus:
Small compact and spherical,
found close to macro nucleus. Fine chromatin granules and threads
uniformly distributed throughout the structure. It controls reproduction. Number varies with species to species.
Nucleolus is absent in caudatum.
5. Contractile Vacuole:
There are
two fluid filled contractile vacuoles, one each at the ends of the body close
to dorsal surface. Their position is fixed between the ectoplasm and endoplasm.
They are temporary organs disappearing periodically. Five to twelve radical canals
are connected to each contractile
vacuole. Each radial canal consists of a terminal part, a long ampula and a short injector canal which opens into the contractile vacuole. The canal
communicate with large part of the body and takes up liquids and pour into the
vacuole. Thus the vacuole increase in size and the liquid discharged outside
during systole through the permanent opening (pore) in the pelged. The two
vacuoles contract irregulargly, the posterior C.V contract more rapidly because
it is close to the cytopharynx and
more water comes to it. The main function of contracted vacuole is osmoregulation and probably involves respiration and excretion.
6. Food Vacuole:
Roughly spherical, non contractile lies varying in size and lying in the endoplasm. They contain digested food particle especially bacteria and small amount of fluid. The digestive granules are associated with the food vacuoles helps in digestion.
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