ParameciumBy: Jillian Bunis

Classification/Diagnostic Characteristics:

The paramecium is a slipper shaped, ciliated cell, belonging to the ciliated class of the phylum Protista. There are several different species of paramecium including caudatum, bursaria, trichium, etc. [1] . The cell is covered by an elaborate pellicle consisting of a double membrane and small, membrane enclosed sacs called alveoli. The alveoli surround the bases of the cilia (these are not the same alveoli found in the pulmonary system.) Also found in the pellicle are defensive organelles, called trichocysts. If the cell is faced with a threat, the trichocysts will explode inside the cell and destroy the threat [2a].

external image paramec.GIF[4]

Relationship to humans:

Paramecium are helpful to humans in many ways. They control algae, bacteria, and other protist populations in nature. They also assist in cleaning up small particles of debris in water, feed small animals, and can live inside the human body (sometimes causing illnesses) [2a]. Paramecium are often used for teaching purposes in classes related to the biological sciences because the organisms are relatively transparent and there are several visible organelles [5,6].
While paramecium do not majorly affect humans directly, they do have a vital role in the food chain. Most Paramecium fall under the category of bacterivorous, and feed on bacteria that accompany dead, decaying matter. These are then consumed by secondary consumers and so forth, until the energy transfer (10% rule) cannot further supply enough energy to sustain life, and so, the food chain fizzes out.

Habitat and niche:

Paramecia live in water bodies such as lakes, puddles, ponds and rivers. They can also live in animal bodies, on plants, or in moist soil; they can survive anywhere with a sufficient amount of water [7]. They form symbiotic relationships with green algae, which live in the cytoplasm. The algae acts as a food source for paramecia.
Niche: Paramecia eat amoeba,green algae, and bacteria. They are eaten by water fleas, mussels, etc. [7].

Predator avoidance:
Paramecia find shelters from their predators by hiding in duckweed, pond lilies, and other water plants. Paramecium are able to rotate 360 degrees to find an escape route when they encounter negative stimuli [9]. Predators include amoeba, water flies, muscles, euglena, scud, nematodes, and flat worms [10].

Nutrient Acquisition:

Paramecia take in solid food via endocytosis. They then form digestive vacuoles within which the food they eat is digested. Later, small vesicles containing the digested food pinch away from the digestive vacuole and move into the cytoplasm. Inside the cytoplasm, the vesicles are absorbed by other organelles in the cell that can utilize the food and turn it into energy [2a].

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Reproduction and Life Cycle:

Paramecia reproduce asexually but can sexually rearrange genetic information. During asexual reproduction, the nuclei are copied before the cell divides. However, the paramecia recombine genetic information sexually; this process is called conjugation. Conjugation occurs when two individuals line up next to each other and fuse together in the oral groove region. Nuclear material is reorganized and exchanged between the two cells (this process takes several hours). After conjugation, each cell ends up with two haploid nuclei (one original and one from the other cell). These two micronuclei then fuse to form a diploid macronucleus [2a].

paramecium-life-cycle.png [11]

Growth and Development:

Because paramecium are such simplistic organisms, they do not undergo major growth stages and do not even experience significant development throughout their life cycles. Once the paramecium reach a certain size, they subdivide into daughter organisms, and the process repeats [12].

images.jpeg [13]

The integument of paramecia includes cilia and pellicles. Pellicles are specialized and flexible membranes. Cilia are small hair like projections out of the cell which allow it to move [14].

Paramecia's cilia are a highly effective form of locomotion. These tiny cells can coordinate the beating of their cilia to propel themselves forwards or backwards [2a].The entire body of the paramecium is covered in tiny hairlike projections called protoplasmic cilia. These cilia are the locomotion organs of the paramecium [2a].


Sensing the Environment:
If the paramecium is disturbed, it will discharge the outer coating of trichocysts. These structures can fire out form the cell in a fraction of a second as the slightest physical or chemical stimulus. When the trichocysts are discharged they may remain attached at their base, until they are finally detached. [2a]

Although the paramecium lacks gustatory, auditory, and visual senses, it can quickly respond to physical sensations, such as those caused by the stimulus of bumping into something. In addition, the paramecium can respond to various chemical concentrations in its environment, such as ones associated with glutamate, a type of salt that functions as an important attractant chemical cue. Glutamate often signals the presence of bacteria, which the paramecium feasts on. The glutamate chemoresponse has several key attributes that allow it to be an effective means of nutrient determination. For instance, there are at least two specific, relatively low affinity glutamate binding sites, regions where the glutamate can weakly bind to the cell surface. Upon attaching to the cell surface, the glutamate hyperpolarizes the cell, meaning that it causes the cell’s membrane potential, the difference in voltage across the cell, to become more negative. This ionic mechanism most likely involves potassium, K+, conductance. The hyperpolarization results in the rapid increase of cAMP, a second messenger involved in activating protein kinase A (PKA), in the cell. Activation of PKA by the rapid spike in cAMP sustains phosphorylation, a process that turns on protein enzymes, and results in activation of the plasma membrane calcium pump. The increase in calcium is thought to be associated with a modification in ciliary movement [16].

Gas Exchange:
Gas exchange in the paramecium is a relatively simple process: oxygen from the surrounding water diffuses in through the cell membrane into the internal environment while carbon dioxide diffuses out through the cell membrane [17].

Waste Removal:
Paramecia excrete waste substances by use of specialized contractile vacuoles that remove excess water that the organisms take in via osmosis. They use their anal pore to dispose of waste [18].

Environmental Physiology (temperature, water, salt regulation):
Paramecia regulate water by way of contractile vacuoles. The contractile vacuoles are where water enters the paramecium body, so if an excess of water enters the vacuole will swell, eventually bursting and releasing water. Water moves from outside to inside of the paramecium because there is a high concentration of water outside as opposed to the low concentration inside because paramecium have salts inside of their vacuoles [19].

Internal Circulation:

Like the Sponge and other organisms with undeveloped internal circulation mechanisms, the Paramecium relies on water movement through the paramecium's pores to serve as a method of internal circulation. The paramecium has no need for a more complex system because of its size, and relying on diffusion of nutrients through water and tidal movement is more energy effective [2a].

Review Questions:
1. Describe how a paramecium achieves movement?
2. Describe the circulation system of the paramecium and the reason for why it is so simple.
3. What is the process in which 2 paramecia come together after meiosis to exchange parts of their genetic material called?
4. Is the surface area to volume ratio the major deciding factor as to when a paramecium undergoes binary fission, or do other biological factors initiate the process?
5. How do paramecia react to stimulus from glutamate?
6. Explain the process in which paramecia obtain their necessary nutrients.


[2a] Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sunderland, MA: Sinauer Associates, 2012. Print.
[2][3][4][5] [GW]