How Many Species of Amoeba are There? – (Let’s Know in Detail)
Amoeba (also spelled ameba) is a genus of protozoa that moves by pseudopodia or false feet. They can easily change their shape and size as they move and feed and do their other activities.
Amoeba is actually the most popular and free-living protozoan that you will find literally everywhere from stagnant water bodies, ponds, lakes, streams, etc. to muddy soil and deep undersoil inside the grasslands.
How Many Species of Amoeba are There? In a broader sense, Amoeba is a genus that falls under the Phylum Amoebozoa. Phylum Amoebozoa is a major and broad taxonomic group containing about more than 2,400 described species of amoeboid protists discovered so far. Whereas, Genus Amoeba contains not more than 20 species discovered so far.
The 20 species discovered under the Genus Amoeba are Amoeba guttala, Amoeba limicola, Amoeba vespertilio, Amoeba discoides, Amoeba dubia, Amoeba leningradensis, Amoeba radiosa, Amoeba assimilis, Amoeba proteus, Amoeba spumosa, Amoeba pigmentifera, Amoeba gorgonia, Amoeba limax, Amoeba chaetognathi, Amoeba agilis, Amoeba verrucosa, Amoeba biddulphiae, Amoeba striata, Amoeba terricola, and Amoeba sphaeronucleolus.
Nevertheless, all of these species resemble each other very well with minute differences and they are often possessing blunt pseudopods and tubular mitochondrial cristae.
In very simple words most Phylum Amoebozoa is a major taxonomic group whereas, Genus Amoeba a minor taxonomic group that falls under Phylum Amoebozoa.
In many of the present classification systems, you will find that Phylum Amoebozoa is ranked within either the Kingdom Protista or the Kingdom Protozoa. Most probably you will find it under the Kingdom Protozoa.
In this post, we’ll not talk majorly about the Phylum Amoebozoa but about the Genus Amoeba that includes not more than 20 species discovered so far.
We will discuss 6 of the well-known and common Amoeba species within the list of the 20 species overall.
How many species of Amoeba are there? List of 6 mentioned below:
1. Amoeba proteus
CLASSIFICATION:
- PHYLUM: Amoebozoa
- CLASS: Lobosa
- ORDER: Amoebida
- FAMILY: Amoebidae
- GENUS: Amoeba
- SPECIES: proteus
HABIT & HABITAT:
It is widely distributed and is commonly found on the bottom mud or on the underside of aquatic vegetation in freshwater ponds, ditches, lakes, springs, pools, and in slow-running streams as well.
You will easily find them at relatively clean ponds with highly oxygenated freshwater as well that contain many algae and plants.
DISTRIBUTION:
It is widely distributed at all those places where there is freshwater pools, ponds, ditches, lakes, slow streams, or damp soils, except in hot water thermals or springs.
DESCRIPTION:
Amoeba proteus is the largest fresh-water form that is mostly used in the various culture methods.
The body of Amoeba is really very simple consisting of a small spot of protoplasm resembling like that of a tiny drop of jelly that has all the cell organelles to perform movement, reproduction, excretion, respiration, etc.
They have pseudopodia to move and feed. They have food vacuole(s) where the ingested food is slowly broken down by enzymes.
It feeds on other protozoans, algae, rotifers, and even other smaller amoebae. Its body appearance is colorless but may have colored inclusions derived from its food.
IDENTIFICATION:
They are unicellular and do have a nucleus with a very thick-walled nuclear membrane containing granular chromatin.
Its membrane includes a phospholipid bilayer similar to other eukaryotic organisms.
2. Amoeba verrucosa
CLASSIFICATION:
- PHYLUM: Amoebozoa
- CLASS: Lobosa
- ORDER: Amoebida
- FAMILY: Amoebidae
- GENUS: Amoeba
- SPECIES: verrucosa
HABIT & HABITAT:
Found in damp aquatic water bodies, in stagnant water bodies, and underside the aquatic plants. Also commonly seen in the ocean water ecosystem.
DISTRIBUTION:
It was discovered in the locality of the Bay of Bengal ocean and in India. It is also seen in some parts of Australia. (No further details have been gathered yet)
DESCRIPTION:
This one is another freshwater species. Their body surface does have a wrinkled appearance, and the body is nearly 0.2 mm in diameter.
The pellicle is highly tough than the other and the pseudopodia are many, short, and blunt. The nucleus is ovoid and contains a large endosome.
The movements of this species are very sluggish and it can literally locomote and move by covering distance of about 0.5 mm per second.
IDENTIFICATION:
It is a kind of very small organism with its body being flattened, ovoid, narrowed, and being rounded posteriorly.
It is vesicular with a single nucleus and with a contractile vacuole which is comparatively large and often not spherical.
The body has an extremely delicate pellicle that shows three or four fine longitudinal lines that appear and disappear with the movement of the body.
3. Amoeba discoides
CLASSIFICATION:
- PHYLUM: Amoebozoa
- CLASS: Lobosa
- ORDER: Amoebida
- FAMILY: Amoebidae
- GENUS: Amoeba
- SPECIES: discoides
HABIT & HABITAT:
Many are often seen as species of soil-dwelling amoeba and also in freshwater ecosystems with highly oxygenated freshwater that contain many algae and plants.
Similar to Amoeba proteus, the habitat of Amoeba discoides habitat small areas of water such as freshwater pools, ponds, lakes, streams, and ditches.
DISTRIBUTION:
Same as Amoeba proteus, it is widely distributed at all those places where there is freshwater pools, ponds, ditches, lakes, slow streams, or damp soils, except in hot water thermals or springs.
DESCRIPTION:
It has a body that is only about 0.4 mm in diameter and with only a few blunt pseudopodia.
The biconcave, discoidal nucleus never become folded like that of Amoeba proteus and the ectoplasmic ridges are also not so well-known.
It’s nucleus have a prominent honeycomb‐like fibrous lamina. The nucleus in the resting and dividing stages is described; division is amitotic.
The more important cytoplasmic contents, including nutritive spheres, and crystals are likewise described.
Their life-history has been worked out. The adult amoeba becomes an agamont giving rise to agametes which eventually grow into adult amoebae, the life-cycle occupying roughly about four months.
IDENTIFICATION:
You will find that when you will place A. discoides in culture with an unlimited supply of Tetrahymena as food organisms for the Amoeba, then it will grow in logarithmic fashion, and the life-span of any clone appears to be unlimited.
4. Amoeba radiosa
CLASSIFICATION:
- PHYLUM: Amoebozoa
- CLASS: Lobosa
- ORDER: Amoebida
- FAMILY: Amoebidae
- GENUS: Amoeba
- SPECIES: radiosa
HABIT & HABITAT:
It can be seen at all freshwater bodies like running water streams, springs, etc. Rarely seen at stagnant water bodies.
DISTRIBUTION:
It is distributed widely majorly at the freshwater bodies.
DESCRIPTION:
This is yet another well-known freshwater species of Amoeba. It is a small freshwater species that is up to 0.04 mm in diameter.
Their body is oval in nature, but the animal looks star-shaped on account of the presence of slender, radiating pseudopodia, which may be stiff and straight, or curved and tapering.
IDENTIFICATION:
It’s unicellular with an easily visible nucleus and a contractile vacuole. The body shows many spiky pseudopodia or false feet.
5. Amoeba dubia
CLASSIFICATION:
- PHYLUM: Amoebozoa
- CLASS: Lobosa
- ORDER: Amoebida
- FAMILY: Amoebidae
- GENUS: Amoeba
- SPECIES: dubia
HABIT & HABITAT:
P. dubium inhabits freshwater and is usually herbivorous, eating algae at all time.
DISTRIBUTION:
Specimens have been collected from North America, and northern Europe continents.
DESCRIPTION:
It is also known as Polychaos dubium. It’s previous name was Amoeba dubia.
Polychaos dubium is a freshwater amoeboid and one of the larger species of a single-celled eukaryote.
Like other amoebozoans, P. dubium moves by means of temporary projections called pseudopods.
It is only about 0.4 mm in diameter with a very smooth and sleek body surface forming several flat pseudopodia.
Their nucleus looks spherical in front view but oblong in profile. The endoplasm is laden with a few large particles of various shapes.
Diatoms form an important item of their diet. The crystals floating in its cytoplasm take the shape of flat bipyramids, flat plates, or clustered platelets.
IDENTIFICATION:
P. dubium lacks longitudinal ridges on its pseudopods.
The nucleus is ellipsoid in shape, has granules next to the membrane, and lacks an endosome.
The cell is usually polypoidal (has many pseudopodia), and the endoplasm and ectoplasm of the cytoplasm are clear.
6. Amoeba terricola
CLASSIFICATION:
- PHYLUM: Amoebozoa
- CLASS: Lobosa
- ORDER: Amoebida
- FAMILY: Amoebidae
- GENUS: Amoeba
- SPECIES: terricola
HABIT & HABITAT:
This can be found on damp and muddy soil. It can also be seen undersoil in the damp ecosystems like in rainforests and all.
It can also be seen in and nearby mosses in various freshwater bodies. They do feed on algae, testate amoebae, fungi, rotifers, etc.
Although they have a traditional reputation as soil and moss inhabitants, they are common in both fresh and saltwater.
DISTRIBUTION:
Found widely in damp soil in and nearby freshwater bodies equipped with mosses.
DESCRIPTION:
It is also called Thecamoeba terricola. It is seen with a tough pellicle simulating a shell.
The unicellular body shows slow movement with usual wrinkles around the body periphery and sometimes fine surface wrinkles extending far-forward from more or less wrinkled, sometimes plicate uroid.
Sometimes small hyaline knobs or scallops on the anterior edge are also seen. The nucleus is an elongate ellipsoid, with rather large parietal nucleolar pieces of various sizes, 14-31 µm.
The atmosphere contains the spores or cysts of Amoeba terricola in a very large numbers.
IDENTIFICATION:
They are often called “amoebae with a pellicle” because of the apparent stiffness of their surface layer with its various folds and wrinkles.
They have a very large nucleus with a usual slow movement as compared to the all other species of Amoeba.
How is Amoeba classified?
The classification system of Amoeba has always been vague and confusing since Amoeba lacks characteristic morphological features.
Also, you will often find that the majority of the other protists resemble the same as Amoeba in many of their appearance and body functioning respectively.
There’s another notable feature you will find, that will help you to better distinguish marine Amoeba from that of the freshwater Amoeba, as the marine Amoeba lacks contractile vacuoles and their enzymes. This is due to evolutionary changes.
Nevertheless, if you see from the genetic point of view you will find that the smaller the species the more genetic contents it does have but the simple the body organization and working it shows. What’s the reason? Nobody knows!
Just for example: The species Amoeba dubia consists of about 370 billion base pairs whereas, the human genome has about 3 billion base pairs.
So, recently there are more advanced scientific studies ongoing to classify Amoeba by using small subunit ribosomal RNA (SSU rRNA) genes.
At present, the Classification of Amoeba is as follows: Amoeba is a Genus of single-celled amoeboids in the Family Amoebidae, of Order Amoebida, of Class Lobosa, of Phylum Amoebozoa.
The current classification is as follows:
- PHYLUM: Amoebozoa (also called Protozoa)
- SUB-PHYLUM: Sarcomastigophora
- SUPER-CLASS: Sarcodina
- CLASS: Lobosa
- ORDER: Amoebida
- FAMILY: Amoebidae
- GENUS: Amoeba
Characteristics of each Taxa:
- PHYLUM: Amoebozoa
- Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, often possessing blunt, fingerlike, lobose pseudopods, and tubular mitochondrial cristae.
- In most classification schemes, Amoebozoa is ranked as a phylum within either the Kingdom Protista or the Kingdom Protozoa.
- Molecular genetic analysis supports Amoebozoa as a monophyletic clade. Most phylogenetic trees identify it as the sister group to Opisthokonta, another major clade that contains both fungi and animals as well as some 300 species of unicellular protists.
- Amoebozoa includes many of the best-known amoeboid organisms, such as Chaos, Entamoeba, Pelomyxa, and the genus Amoeba itself.
- SUB-PHYLUM: Sarcomastigophora
- Locomotor organelles pseudopodia or flagella or both.
- Nuclei is of one kind (monomorphic).
- SUPER-CLASS: Sarcodina
- Body mostly amoeboid without a definite pellicle. Some with skeleton of some kind.
- Locomotion by pseudopodia.
- Nutrition holozoic or saprozoic.
- CLASS: Lobosa
- Presence of pseudopodia or lobopodia
- ORDER: Amoebida
- Body is amoeboid, naked, and without skeleton.
- Nucleus with honeycomb lattice.
- Largely freshwater and free-living. Many of the organisms are also parasitic.
- FAMILY: Amoebidae
- Includes naked amoebae that produce multiple pseudopodia of indeterminate length.
- During locomotion one pseudopod typically becomes dominant and the others are retracted as the body flows into it.
- GENUS: Amoeba
- Minute animalcules that live solitary or by forming loose colonies.
- Body is naked and bound by pellicle.
- It’s unicellular and the single cell performs all the vital living activities.
- Locomotes and moves using pseudopodia.
- Nutrition is holozoic, holophytic, saprophytic, and parasitic.
- Contractile vacuole serves mainly for osmoregulation.
Is Amoeba a plant or an animal?
An amoeba is animal-like, but it is neither an animal nor a plant. It falls under the Animal studies and is well-studied in the Zoological textbooks and research papers.
It’s not an animal, it’s an animalcule because of its very minute size.
It is not considered plants because of its ability to move, as it has pseudopodia to locomote and move. It searches for its own food and feeds on them using the various feeding mechanisms of its pseudopodia.
It is often seen that they can perform photosynthesis if the light is present, and also in absence of light become heterotrophic. This doesn’t mean that they are always photosynthetic like plants.
Some Amoeba species like Dictyostelium discoideum become photosynthetic only when they can engulf photosynthetic bacteria within its cell to become photosynthetic itself.
Another clear-cut reason is that the Amoeba cell doesn’t possess any cell wall or chlorophyll therefore it doesn’t belong to plants.
So, in simple words Amoeba is neither a plant nor an animal. It’s complex nature, fits them neither into Kingdom Animalia, nor into Kingdom Plantae, but fits it either in the Kingdom Protista or Kingdom Protozoa. So, it is better known as Animalcule.
Kingdom Protista/Protozoa is pretty much a catch-all kingdom for things like slime molds, paramecia, and amoebas that don’t fit any other category.
