Paramecium. Sub-Order Peniculina. Genus Paramecium

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Carmel Stephens
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1 Paramecium Kingdom Animalia Phylum Protozoa Sub-Phylum Ciliophora Class Ciliata or Infusoria Sub-Class Holotricha Order Hymenostomatida Sub-Order Peniculina Family Paramecidae Genus Paramecium Introduction: - Paramecia are minute organisms just visible to the naked eyes as elongated whitish or grayish spots. It differes from Amoeba in having a permanent body shape. History: - The name Chausson given to Paramecium Caudatum by Joblot means slipper shaped animal. The generic name Paramecium (Gr. Paramekos Oblong) given by John Hill in Habit & Habitat: - Paramecium is perhaps the commonest ciliate found everywhere in freshwater i.e. ponds, pools, ditches, river, lakes etc. It is specially

2 abundant in organic infusions i.e. in stagnant water containing decaying organic matter feeding upon the bacteria & tiny protozoa that swam in such water. It is free living & found float on the water surface. External Feature: - Shape & Size: - Under microscope it looks rather elongated and cigar shaped or slipper shaped & hence called slipper animalcule. It is 180 "&m 300 "&mm long & "&m wide [Largest species P.Caudatum "&m] The anterior end is broad & rounded while the posterior end is more or less pointed.

3 The upper dorsal or aboral surface is convey while the ventral or oral surface is concave & thicker. It has greatest diameter just behind the centre of the body. The ventral surface shows a large shallow oblique depression, the oral groove which posteriorly leads to a deeper conical vestibule which in turn communicates with a buccal cavity having a basal mouth or hypostome. The ectoplasm secretes or colorless, thin, firm, elastic & cuticular membrane which covered the body is called pellicle or, periplast which is responsible for a definite & constant shape of the paramecium. The surface of pelliclee has a great number of polygonal or hexagonal areas bearing the opening of trichocyst. Each hexagonal areas has a central depression or circum ciliary space from which a cilium comes out. All cilia are equal in size except those of the posterior end which are longer and called caudal tuft. The cilia originate from the basal granules or kinetesomes. [cilia "& in length and 0.27 "& in diameter, 10,000 14,000 in number] Internal Structure: - The cytoplasm beneath the pellicle is clearly differentiated into two regions i.e. outer ectoplasm or cortex & inner endoplasm or medulla.

4 Ectoplasm: - It surrounds the inner mass of the endoplasm forms a clear, dense, thin peripheral layer which is tough, elastic, supporting & protective. It contains basal bodies of cilia or kinetosome, kinetodesmata and trichocyst. Kinetosome: - The cilium is joint to a solid body below the pellicle is called kinetesome or basal granules or basal body. It is self reproducing unit and progenitors of new cilia. It is either centriole or its derivatives.

5 Kinetodesmata: - In paramecium a single ciliary rootlet or fibril called kinetodesmos or km fibrils arises from each kinetosome and runs for some distance tapering anteriorly. Trichocyst: - Numerous peculiar, tiny spindle shaped or cigar shaped organelles present beneath the pellicle. Each trichocyst is a minute organelle measuring 4 "& by 2 "&. It opens to the exterior through a minute pore present on the ridge of hexagonal areas of pellicle.

6 The trichocysts contain a shaft with a terminal pointed tip called the spike or barb covered by a cap. When the animal is irritated, the protoplasm surrounding the trichocysts suddenly contracts, the caps of trichocysts lifted and water fills in. The swelling substance expands and is discharged as long sticky threads which serve as organs of defense. Endoplasm: - Below the ectoplasm is a semi fluid granular endoplasm which shows a streaming movement called cyclosis. It contains nucleus, contractile vacuole, food vacuole, reserve food granules of starch, glycogen & fat, mitochondria. Golgi bodies, ribosomes & other cytoplasmic inclusions of varying size, shape & character.

7 Nuclear apparatus: - The nuclear apparatus of paramecium shows dimorphic nature. It has two types of nuclei i.e. heterokaryotic. A. Large macro or mega nucleus: - It is granular and roughly kidney shaped or bean shaped & without a nuclear membrane. It contains many nucleoli. It controls all the vital activities of the body except reproduction, hence it is called trophic or vegetative nucleus. It is derived from the micronucleus during reproductive processes and always divides amitotically. B. A smaller micronucleus: - It is lodged in a depression on the surface of the meganucleus. It is usually spherical and with a definite nuclear membrane. It controls the reproductive activities of the organism and undergoes mitosis or meiosis. Contractive Vacuole: - Between the ectoplasm & endoplasm near each end, towards the dorsal surface is a large C.V.. The position of C.V. is definite but they are temporary structure. Around each C.V. are 6 10 radiating or feeder canals in the endoplasm. The vacuoles are excretory, they remove ammonium compound & CO 2 but their primary function is hydrostatic or osmoregulatory in function.

9 Food Vacuole: - Recently termed gastrioles by valvosky. They differ in shape and size according to the nature of the ingested food particles, but mostly they are rounded in forms can be seen moving with cyclosis. It is non-contractile in nature.

Unit 4 Protists and Fungi

Unit 4 Protists and Fungi Objectives Topic 1: Protists Protists are eukaryotes that are not members of the kingdoms, Plantae, Animalia, or Fungi Identify the defining characteristics of animal-like, plant-like