Difference Between Amoeba and Entamoeba

Main Difference – Amoeba vs Entamoeba

Amoeba and Entamoeba are two types of unicellular microorganisms that belong to the kingdom Protista. Both Amoeba and Entamoeba are two genera of the phylum Amoebazoa. The main difference between Amoeba and Entamoeba is that Amoeba is a freshwater organism whereas Entamoeba lives as an internal parasite inside animals. Amoeba feeds on algae and plankton. The movement of Amoeba occurs by means of pseudopodia (false feet). Pseudopodia is an extension in a region of the cytoplasm. Entamoeba lacks mitochondria. Instead, normal flora lives in symbiotic relationships inside Entamoeba. Entamoeba causes amoebic dysentery in humans and other animals.

Key Areas Covered

1. What is Amoeba
      – Definition, Habitat, Features
2. What is Entamoeba
      – Definition, Habitat, Features
3. What are the Similarities Between Amoeba and Entamoeba
      – Outline of Common Features
4. What is the Difference Between Amoeba and Entamoeba
      – Comparison of Key Differences

Key Terms: Amoeba, Entamoeba, Infective Cyst, Parasites, Protists, Pseudopodia, Trophozoites

What is Amoeba

Amoeba refers to single-celled freshwater protozoa, which possess pseudopodia. It is characterized by the presence of a granular nucleus surrounded by a jelly-like mass of cytoplasm. Though most amoebae are free-living, a few may live as parasites. Due to the presence of pseudopodia, amoeba cell is irregular in shape. The diameter of an amoeba can be 0.1 mm. The cell membrane of the amoeba comprises an outer and an inner endoplasm. Amoeba cell contains food vacuoles and contractile vacuoles in its single-celled body. The propagation of amoeba occurs by forwarding its cytoplasm. The formation of pseudopodium allows amoeba to move slowly. The pseudopodium is also called false foot. This movement is referred to as amoeboid movement. Typically, amoeba eats bacteria, algae, plant cells, and other microscopic organisms. The process of feeding is referred to as phagocytosis in which pseudopodia is formed to engulf the food particle. The engulfed food is digested inside a vacuole in the body and wastes are eliminated by exocytosis. An Amoeba engulfing a diatom is shown in video 1.

Video 1: An Amoeba engulfing a diatom

Amoeba reproduces asexually by binary fission and formation of spores. Under favorable conditions, binary fission produces daughter cells by mitotic cell divisions of a parent cell. Spores are formed in dry conditions and during insufficiency of food and those spores are germinated under favorable conditions. Amoeba is sensitive to external stimuli such as the change in light, temperature, and chemicals. It is also sensitive to touch.

What is Entamoeba

Entamoeba refers to any protozoa of the genus Entamoeba, which is parasitic in vertebrates. It may live as parasites inside some invertebrates and unicellular eukaryotes as well. The life cycle of Entamoeba consists of an infective cyst. A multiplying trophozoite stage can also be identified in their life cycle. The transmission of Entamoeba can occur through the ingestion of food that is contaminated with cysts. Entamoeba histolytica causes amoebic dysentery in humans and other animals. During amoebic dysentery, the intestinal wall is invaded by the trophozoites. Trophozoites also cause ameboic liver abscess and other extraintestinal lesions. The trophozoites of Entamoeba histolytica is shown in figure 2.

Figure 2: Trophozoites of Entamoeba histolytica

An entamoeba cell contains a single nucleus with a single lobose pseudopod. The size of a trophozoite is around 10 – 20 μm in diameter.

Similarities Between Amoeba and Entamoeba

Both Amoeba and Entamoeba belong to the phylum Amoebazoa under the kingdom Protista.
Both Amoeba and Entamoeba move by forming pseudopodia.
Both Amoeba and Entamoeba possess an irregular-shaped body.
Both Amoeba and Entamoeba asexually reproduce through binary fission.

Definition

Amoeba: Amoeba refers to single-celled freshwater protozoa, which possess pseudopodia.

Entamoeba: Entamoeba refers to any protozoa of the genus Entamoeba, which is parasitic in vertebrates.

Class

Amoeba: Amoeba belongs to the class Tubulinea.

Entamoeba: Entamoeba belongs to the class Archamoebae.

Family

Amoeba: Amoeba belongs to the family Amoebidae.

Entamoeba: Entamoeba belongs to the family Entamobidae.

Habitat

Amoeba: Amoeba lives in freshwater habitats.

Entamoeba: Entamoeba lives as internal parasites inside animals.

Mode of Nutrition

Amoeba: Amoeba is a heterotrophic microorganism that eats plankton and algae.

Entamoeba: Entamoeba is a parasite.

Mitochondria

Amoeba: Amoeba consists of mitochondria.

Entamoeba: Entamoeba lacks mitochondria.

Contractile Vacuole

Amoeba: Amoeba consists of a contractile vacuole, involved in the osmoregulation.

Entamoeba: Entamoeba lacks contractile vacuoles.

Diseases

Amoeba: Amoeba may cause meningoencephalitis, naegleriasis, and infections.

Entamoeba: Entamoeba histolytica causes amoebiasis.

Examples

Amoeba: Pelomyxa, Radiolarians, and Foraminifera are examples of Amoeba.

Entamoeba: Entamoeba histolytica, E. bangladeshi, and E. bovis are some examples of Entamoeba.

Conclusion

Amoeba and Entamoeba are two genera of the phylum Amoebazoa under the kingdom Protista. Both Amoeba and Entamoeba are composed of pseudopodia. Amoeba is mostly a free-living organism in freshwater habitats. It eats plankton and algae. Entamoeba lives as parasites inside animals. Hence, the main difference between Amoeba and Entamoeba is their habitat and mode of nutrition.

Reference:

1. “Classification of Amoeba (Ameba).” BiologyWise, Available here.
2. “Basic Information on Entamoeba.” Entamoeba Basics, Available here.

Image Courtesy:

1. “Amoeba engulfing diatom” by Deuterostome (CC BY-SA 3.0) via Commons Wikimedia
2. “Entamoeba histolytica” By Stefan Walkowski – Own work (CC BY-SA 3.0) via Commons Wikimedia