"Amoeba (Amöbe) - Vahlkampfia sp - 630x" by Picturepest is licensed under CC BY 2.0
Definition of Rhizopods
The term rhizopoda comes from the Greek, namely rhizo which means "root" and podos which means "foot". Thus, Rhizopoda means feet that resemble roots. Rhizopoda is a Protozoa that has a means of locomotion in the form of pseudo-legs (pseudopodia). Called pseudopodia or pseudopods because they are formed as a result of the protrusion of the cytoplasm of the cell, which seems to function as legs. In addition to moving, pseudopodia also function to find food.
Currently, about 40,000 species of Rhizopoda or Sarcodina are known, namely Protozoa whose shape is not fixed, always changing. One of the most famous examples of Rhizopoda members is the Amoeba which can live in fresh water, salt water, in moist soil, and some species live as parasites on animals and humans.
When moving, the Amoeba will extend the pseudopodia and hook the ends then release more cytoplasm into the pseudopodia. This kind of motion is called amoeboid motion . With this pseudo-leg, it means that the shape of Rhizopoda cells changes both at rest and when moving.
Characteristics of Rhizopods
Rhizopoda or Sarcodina has several characteristics or characteristics that distinguish it from the other three types of Protozoa . In the following, the authors describe the characteristics of Rhizopods in general.
■ Moving with false feet (pseudopodia).
■ Characteristically microscopic, as most have a body size of about 200 - 300 microns.
■ Having a form of cell that is not fixed alias changeable (ex. Amoeba ).
■ Some types have a shell or external skeleton (ex. Foraminifera and Radiolaria ).
■ Characteristically heterotrophic, meaning it can not make their own food substances so as to meet their nutritional needs, Rhizopoda must prey on other organisms.
■ Live free (solitary) or parasites.
■ Swallowing food particles by phagocytosis .
■ Breathe by diffusion across the surface of the body.
■ The cytoplasm consists of ectoplasm and endoplasmic.
■ Have a cavity in the form of food vacuole to digest food.
■ Have a contractile vacuole which serves to remove waste products of metabolism and to regulate the osmotic pressure of the body.
■ Have habitat in fresh water, sea water, wet places and a small part of life in animals or humans.
■ Some species can form cysts, which form a plasma thickening which serves to protect themselves from unfavorable environment.
Classification of Rhizopods
Class Rhizopoda or pseudo-legged animals are divided into 5 kinds of orders, namely the order Labosa, order Filosa, order Foraminifera, order Helioza and order Radiolarian. The characteristics or characteristics of each order are as follows.
■ Order Labosa , its features is to have pseudopodia (false feet) short and blunt and can be clearly distinguished between ectoplasm and endoplasmic.
■ Order Filosa , its features is to have a smooth pseudopodia similar to the yarn and also branched.
■ Order of Foraminifera , its features is to have a long pseudopodia and also smooth and has a skeleton of lime (calcium carbonate).
■ Order Helioza , its features is to have the thread-shaped pseudopodia radien and antarfilamen were never united to form the mesh or webbing.
■ Order Radiozoa , its features is to have a frame made of silica.
How to Reproduce Rhizopods
Rhizopods (ex. Amoeba ) reproduce asexually or vegetatively by binary fission. Binary fission in Rhizopods does not go through the stages of mitosis. Cleavage begins with the splitting of the cell nucleus into two, followed by the division of the cytoplasm. The division of the nucleus creates a very deep indentation that will eventually break, resulting in two daughter cells. The two daughter cells will undergo binary fission again so that they become four, eight, sixteen cells and so on.
In unfavorable conditions, Rhizopods can survive by forming cysts, namely with the inactive body turning into a round shape so that the plasma membrane thickens to protect the body from adverse external conditions. If the external conditions are favorable, for example there is enough food, then the kisat wall will break and the Rhizopoda will come out to start its life again.
Examples and Roles of Rhizopods in Life
Similar to Flagellates, organisms belonging to the Rhizopoda class also have various important roles for human life, both harmful and beneficial. Then what is the role of this Rhizopoda? Here are some examples of Rhizopod organisms and their role in life.
1. Amoeba
Based on their habitat or place of life, Amoeba is divided into two genera, namely Ectoamoeba and Entamoeba genus . The following are the differences and examples of species from the two Amoeba genera .
A. Ectoamoeba
Ectoamoeba are amoeba that live freely outside the body of living things. They usually live in humid places. Examples of ectoamoeba are Amoeba proteus and Chaos carolinese .
B. Entamoeba
Entamoeba is an amoeba that lives in the body of organisms (animals and humans) and usually causes disease to the host organism it lives on. Examples of Entamoeba are as follows.
■ Entamoeba histolytica , the parasite lives in the human intestine and can cause dysentery amoebawi or known by the disease amebiasis . Amebiasis is a disease that causes damage to body tissues, especially erythrocytes (red blood cells) and lymph, causing the patient's face to be mixed with blood and mucus.
■ Entamoeba ginggivalis , live as parasites in the mouth that can cause inflammation and bleeding gums disease. This amoeba can live in between dirty teeth. In order not to get attacked, brush your teeth after eating and before going to bed.
■ Entamoeba coli , live in the colon (large intestine) man who is not a parasite but sometimes cause diarrhea (defecate constantly).
2. Foraminifera
Foraminifera have shells of organic matter and hard calcium carbonate. Foraminifera live in piles of sand or attached to plankton, algae and rocks. Pseudopodia or pseudo-legs are cytoplasmic strands that function to swim, catch prey and form shells.
About 90% of Foraminifera have been fossilized and their shells are components of oceanic sediments. Foraminifera fossils are used as markers of the age of sedimentary rocks and clues in the search for petroleum sources. An example of Foraminifera is Globigerina .
3. Radiolaria
Radiolaria live in the sea, the shell is made of silica with different shapes in each species. The dead radiolaria will settle to the bottom of the water as radiolarian mud. Radiolarian mud is used as a scouring agent and explosives. Examples are Colosphaera and Acanthometron.
4. Dyflugia, Arcella and Helioza
These three types of Rhizopods live in fresh water. Diflugia can produce mucus that causes fine grains of sand to stick together. Arcella has a shell composed of chitin or phosphoprotein substances. The upper body shell is dome-shaped, while the lower part is concave with holes for the exit of pseudopodia. Helioza (solar animals) have pseudopodia that are rigid and shells containing chitin or silica like glass.
