The following points highlight the two examples of Ciliated Protozoans. The examples are: 1. Paramecium 2. Balantidium coli.
Example # 1. Paramecium:
The Slipper Organism or Slipper Animalcule. Paramecium is a free-living ciliate which is found in fresh water. Most widely distributed species are Paramecium caudatum and Paramecium aurelia. Nutrition is microphageal. Bacteria are its chief food. Paramecium is a surface feeder. Pellicle maintains the shape.
The cilia of the extreme posterior end are longer and form a bunch called caudal tuft. The discharged trichocysts serve for anchoring or defence or it may be a reaction to injury. Feeding Apparatus consists of peristome (= oral groove), vestibule, buccal cavity, cytostome (= cell mouth) and cytopharynx.
The latter opens into the endoplasm. A temporary opening, called cytopyge (= cytoproct or cell anus), is present a little behind the cytostome. Undigested food is passed out through cytopyge. Paramecium caudatum contains a single large macronucleus and one small micronucleus. Paramecium aurelia has one macronucleus and two micronuclei.
Paramecium contains two contractile vacuoles surrounded by 5 to 12 radial (feeding) canals. The contractile vacuoles and radial canals are for osmoregulation. Several non-con-tractile food vacuoles (= gastrioles) are seen moving along definite course (cyclosis) within the streaming endoplasm. The food vacuoles are meant for intracellular digestion.
Both asexual and sexual reproductions are found in Paramecium. Asexual reproduction occurs through transverse binary fission. Various methods of sexual reproduction in Paramecium are conjugation, autogamy — it corresponds to self-fertilization, endomixis — it corresponds to parthenogenesis, cytogamy — it shows the characters of both conjugation and autogamy, and hemixis – only the macronucleus takes part in hemixis.
In hemixis the macronucleus first breaks into a few irregular pieces; later some pieces reunite to form the macronucleus. Remaining pieces disintegrate in the endoplasm. Thus hemixis is called Purification Act.
Two types of Paramecia are reported:
(a) Killer Paramecia contain Kappa Particles:
The latter have DNA and RNA. Killer Paramecium produces a poisonous substance, called paramecin which kills sensitive Paramecia.
(b) Sensitive Paramecia:
Do not contain Kappa particles and hence do not secrete paramecin.
Paramecium exhibits cytoplasmic inheritance in the occurrence of Kappa particles.
Example # 2. Balantidium Coli:
This ciliate lives as an endoparasite in large intestine of human beings. It causes ciliary dysentery which is characterized by diarrhea and ulceration of large intestine. The transmission of parasite is through cysts in contaminated food or water. Carbarsone, Aureomycin and Terramycin are ideal medicine for curing the ciliary dysentery.