Paramoecium is an acellular slipper-shaped ciliate or slipper animalcule. It occurs in freshwater. The outermost cuticular membrane of the Paramoecium is cuticular membrane of the Paramoecium is pellicle which secreted by ectoplasm. The ectoplasm contains bottle-shaped organelle called trichocyst.

Trichocyst discharges a fibrous protein trichonin and it acts as an organelle of defence and anchoring. Cilla, the tiny protoplasmic processes, cover the entire body. Each cilium arises from the cytoplasmic granule called basal body or kinetesome.

The kinetesome, kinetodesmata (associated fibril) from infraciliary system in the ectoplasm. The endoplasm contains nucleus, two contractile vacuoles, food vacuoles and other organelles. In Pbursaria the endoplasm is filled with a unicellular symbiotic alga called zoochlorella. Nucleus in heterokaryotic (2 types) – meganucleus and micronucleus.

Meganucleus control metabolic activity and micronucleus reproductive activity. Paramoecium caudatum has one micronucleus caudatum has one micronucleus and P.aurella has 2 micronuclei.


They produce asexually by transverse binary fission and sexually by conjugation(exchange of micronuclear materials between two Paramoecia), autogamy, cytogamy and endomixis.

Systematic Position:

Kingdom – Protista

Phylum – Protozoa


Sub–Phylum – Ciliophora

Class – Ciliata

Genus – Paramecium

Species – Caudatum.