Paramecium

Paramecium is a genus of single-celled protozoans with cilia, in the class Ciliophora. Found free living in fresh water, paramecia are easily recognized under the microscope by their distinctive slipper shape. The body surface is covered with numerous cilia used for the organism’s spiraling locomotion. The water currents thus produced help funnel bacteria, the paramecium’s usual food, into the mouth, which is situated at the end of the oral groove, a ciliated channel. A food vacuole forms around the food and travels in a cyclic manner in the cytoplasm. The vacuole’s contents are subjected to digestive enzymes, and the products of digestion are diffused into the cytoplasm. Undigested material is released at the posterior end of through several permanently located contractile vacuoles, which produce star-shaped tubes in the water collecting process.

Sexual reproduction in Paramecium is achieved through an exchange of chromosome containing nuclei between two temporarily united paramecia. Genetic characters are passed to offspring by nuclear reorganization and duplication followed by a simple pinching into two cells. Paramecia also reproduce asexually through binary fission.

Paramecium Caudatum, only peripheral cilia are shown, for charity. cv, contractile vauole; fv, food vacuole; m, micronucleus; N, macronucleus; OG, oral groove; Ps pristome (vuccal cavity); cs, cytosome; ffv, forming food facuole.