The biological world of living organisms is full of wonders. There is no doubt that you can see and enjoy the beauty of nature as is, but the true beauty of nature can be seen when you start observing the characteristics and fascinating features of microorganisms under a microscope. That is when you will be simply spellbound with the splendor of nature. Paramecium is a group of unicellular ciliate protozoa. They belong to the kingdom protista, class ciliatea and family parameciidae. Several species of genus paramecium are known and studied, for instance, aurelia, bursaria, caudatum, trichium, etc.
Though characteristics of paramecium are different from the characteristics of normal animals, it belongs to the group of living organisms and is a part of the living world. Paramecia have no eyes, no ears, no brain and no heart; but still, they undergo all life and growth processes like locomotion, digestion and reproduction and you can observe all these processes under a microscope.
Paramecium size ranges from about 50 to 350 μm in length. The cell is covered by cilia (short, hairlike projections of the cell), which allow the cell to move with a synchronous motion (like a caterpillar). It is one of the well-studied unicellular organisms, that is found in almost all types of aquatic environment. It widely spreads in freshwater environment and is especially present in scums. Recently, some new species of Paramecia have been discovered in the oceans.
One of the interesting paramecium facts is that it has a deep oral groove from where food is drawn inside. Paramecia generally feed on bacteria, other small cells, yeast or small algae. The cilia help catch the food which is then forced down a little tube called a gullet, that leads to the protoplasm or stuffing of the cell. The food is held in little vacuoles.
A pair of contractile vacuoles pumps excess water out of the cell. Water is absorbed by osmosis from the cell's surroundings and the pair of vacuoles is responsible for the process of osmoregulation (regulation of the osmotic pressure of the fluids in an organism). Oxygen and carbon dioxide pass through the cell membrane of the paramecium cell.
The stiff outer covering of the paramecium gives it a permanent 'slipper' like shape. The exterior membrane of the cell is known as 'pellicle'. It is stiff as well as flexible. Some flexing of the surface is possible because of this membrane. The cilia help paramecia to move. They can move at speeds of approximately 2,700 μm/second (12 body lengths per second). One of the amazing paramecium facts is that although it normally moves forward in a corkscrew manner, it is capable of reversing its direction when it encounters an adverse condition! To observe this trial-and-error behavior (backing up and then continuing forward in a slightly different direction until the correct path is found) through a microscope is a breathtaking site.
Besides having an oral groove, paramecia have an anal pore, two contractile vacuoles that regulate the water content of the cell and two nuclei. The larger nucleus called macro-nucleus plays an important role in regulating most cell functions, while the smaller nucleus, known as micro-nucleus, is responsible for paramecium reproduction.
Paramecium reproduction usually takes place asexually, by cell division; but the unicellular organism can even interchange the genetic information through a process called conjugation. Just like amoeba, the paramecium cell splits in half (fission). Initially, the smaller nucleus divides itself into two halves and each half goes to either end of the paramecium. Then the bigger nucleus divides and the whole paramecium splits.
During the process of conjugation, two paramecia join at the oral grooves and interchange micro-nuclei that are in fact nothing but little packages of DNA. After the union, the cells divide, producing daughter cells with DNA from each of the parents.
Paramecium facts inform us that though paramecium is an unicellular organism, the cell contains everything needed for survival. Most paramecia are microscopic and over 80,000 different species of paramecia have been so far identified. Though they can be seen with naked eyes, microscope is required to study the structure and behavior of paramecia. I hope you found the above facts interesting.