Paramecium is a unicellular organism belonging to genus, Protozoa. Like many other Protozoa, paramecium has ciliated body that aids in locomotion. The habitants of protozoa vary from fresh water bodies, marine water, brackish and stagnant waters in in basins and ponds, (Ladenburger 7). Some species of paramecium can easily be cultivated and induced to conjugate. Due to these characteristics, paramecium has been used in laboratories for research purposes. The body of a paramecium is covered by cytoplasmic structures which are called cilia. Cilia are hair like structures which helps the organism in movement. The flickering movement of cilia propels the organism hence enables it to move. Paramecium has got cellulose cell-wall which enables it to have distinct shape. Unlike amoeba, paramecium has distinct permanent shape. Each and every cell organelle in paramecium cell has a distinct purpose; they occupy specific area of the cytoplasm, (Ladenburger 13).
Osmoregulation is a process by which an organism maintains a homeostatic balance between the body fluid and the surrounding environment or cells. Single-cellular organisms have to maintain homeostatic balance between the cytoplasm and the surrounding habitat. Paramecia are adapted in a way to help them maintain the concentration of the body fluid so that it does not become too dilute or too concentrated. To maintain osmoregulation, paramecium has a contractile vacuole where water absorbed as a result of the osmotic gradient, accumulate, and move towards the cell wall and release the water through the pores (Wassmer 18). The organism ingests the food through cytostome. Paramecium reproduces through binary fusion. This is an asexual reproduction where the mature organism divides to form new organisms. After feeding on single celled algae and fungi, paramecium absorbs the food for energy and cell division. The waste material is produced in form of urea, calcium, potassium, sodium, etc. The figure 1 below shows a diagram of a paramecium.
Figure 1: A diagram of Paramecium: D G Mackean. Biology Teaching Resources. Educational Articles, 2016: http://www.biology-resources.com/paramecium-01.html
The waste materials from paramecium, after digestion, then accumulated in the cytoplasm. Because plasmodium lives in fresh water, there will be high concentration of solute in the body of the plasmodium than the outer environment. This great concentration gradient between the body of the plasmodium and the surrounding causes osmotic potential to the plasmodium cell, (Wassmer 25). Due to osmosis, we expect that water will be drawn from the surrounding into the plasmodium cell making it burst. However, plasmodium is well adapted to the condition which enables it to survive such great osmotic difference.
The contractile vacuoles of ciliates are permanent structures that theoretically squeeze out excess water through a tiny pore. In some paramecium the contractile vacuole have conspicuous feeder arms. But in most ciliates, the canal system is less apparent and the contractile vacuole appears as a simple sphere, (Ladenburger 21). After some time, the concentration of the waste materials reaches a level that has to be eliminated. Water is then drawn into the cell through osmosis. Water mixes with the nitrogenous wastes and is pumped through the feeder arms into the contractile vacuole. The contractile vacuole then starts to move towards the periphery of the cell. Upon reaching the cell membrane, the contractile vacuole squeezes thereby releasing the excess water and mineral salt through the pores available on the walls. Paramecium has two contractile vacuoles, this increases the surface are for excretion of waste materials. This is the mechanism paramecium uses to avoid bursting in fresh water as a result osmotic pressure.
References
Ladenburger, Eva-Maria, et al. "An Ins (1, 4, 5) P3 receptor in Paramecium is associated with the osmoregulatory system." Journal of cell science 119.17 (2006): 3705-3717.
Wassmer, Thomas, et al. "The V-ATPase in Paramecium: functional specialization by multiple gene isoforms." Pflügers Archiv-European Journal of Physiology 457.3 (2009): 599-607.
