The Pseudopodia Are temporary projections filled with cytoplasm of the membrane of a eukaryotic cell or of a unicellular protist. Pseudopodia can be used for mobility, or to ingest nutrients and particulate matter.
The Cells Which make up the pseudopods are generally referred to as ameboids. Pseudopods extend and contract by the reversible process of actin subunits in many microfilaments.
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The filaments near the cell interact with the myosin, which causes a contraction. The pseudopods extend until the actin reassembles itself into a channel.
The pseudopods are made up of filament structures and micro tubules. The functions of the pseudopods include the locomotion and the capture of the prey. Pseudopods are keys to feeling prey that can be swallowed.
Many pseudopods arise from the surface of the body (as in the amoeba); In other cases, a single pseudopod can be formed on the surface of a body (as in It was histolytic ).
Pseudopods do not always look like amorphous masses; Rather they may be classified by their distinctive appearances. They can be classified in the following varieties: lobopods, filopods, reticulopods and axopods.
Functions of pseudopodia
Usually they have two functions: the locomotion and the capture of prey or the swallowing of food. For example, the amoeba can be dragged by extending the cytoplasm And shrinkage of filaments.
On the other hand, they are also used to capture and ingest prey. They can ingest particulate matter while providing mobility during food hunting.
They are also needed to feel a prey nearby, which helps organisms like amoeba to ingest matter through the process of Phagocytosis .
In that process, these projections envelop the particle of food. In this way they create a sack trapped in a tightening membrane; Creating a Vacuole Of food before the food is completely digested.
Examples
Many genera of the Protist Kingdom use pseudopods to move and eat food. While pseudopodia are often classified as characteristics of protists, they do not really restrict that classification.
The cells of some animals form pseudopodia. For example, white cells of vertebrate animals use pseudopodia to ingest foreign particles, such as bacteria and viruses, in a process called phagocytosis.
Pseudopodia are a feature of a group of organisms called rhizopods. White cells of the immune system use pseudopodia to crawl inside bodies.
Varieties
Lobopodio
They are pseudopods that look like fingers; Is the most common type observed in nature. They are characterized by being bulbous and short projections, which contain endoplasm and ectoplasm.
An example of a lobopod is the loose amoeba, which is considered the largest pseudopod.
Amoebozoa
They are a large taxonomic group containing about 2,400 species of ameboid protists. They often contain lobular and tubular pseudopodia.
This group includes many of the best known amoeboid organisms, such as Chaos , the Entamoeba, the Pelomyxa And the same Amoeba .
Many of the species of this genus are commonly found in salt and fresh water; As well as on the soil, moss and leaves. Some live as parasites of other organisms, or can cause diseases in organisms.
Amoebiasis, a common infection in humans, is caused by amoebas of the group Entamoeba . About 480 million people are infected; Between 40,000 and 110,000 people die each year from this infection.
Most amoboezas are unicellular, but some types have multicellular stages of life in which aggregate cells produce spores. This species varies in size: from 10mm in diameter to 800mm.
Filopodia
They are thin cytoplasmic projections that extend above the border of the lamellipods in migratory cells. These projections are supported by microfilaments. The filopodia are filiform and have sharp edges that are made of ectoplasm.
Philopodia have roles in the sense, migration and interaction between cells. To close a wound in vertebrates, growth factors stimulate the formation of filopodia in fibroplasts to direct fibroplast migration and wound saturation.
Filopodia are also used for the movement of bacteria between cells, to evade the immune system of the host.
Some examples include Lecithium and the Euglypha . Interestingly, this type of filopodia can have variations.
For example, granulopodia is similar to filopodia, but has a granular structure called extrusoma that specializes in capturing prey rather than mobility.
Axopodias
They are thin pseudopodia that contain complex groups of microtubules and are enveloped by cytoplasm.
Axopodias are primarily responsible for phagocytosis and intake of food particles, as they retracted rapidly in response to physical contact.
Protists of the genre Radiolaria Y Heliozoa Are examples of this type of pseudopod.
Radiolaria
They are 0.1-0.2 mm diameter protozoa that produce mineral skeletons, typically with a central capsule that divides the cell into the inner and outer portions of the endoplasm and ectoplasm. The mineral skeleton is usually made of silica.
They can be found in the Zooplankton Along the ocean; Its skeletal remnants make up a large part of the ocean floor deck. They represent important diagnostic fossils found from the Cambrian Period onwards.
Radiolarias have many pseudopods that look like needles; Also have groups of micro tubules that make the radiolarias appear abundant and leafy.
Reticulopida
They are complex formations where pseudopodia are combined to form irregular networks and communicate with other pseudopods. The primary function of reticulopida is the ingestion of food; Locomotion is the secondary function.
Reticulopods are typical Foraminifera
Foraminifera
They are members of ameboid protists characterized by: channeling granular ectoplasms to trap food and having an outer shell of various shapes and materials.
Most of the Foraminifera They are marine; Live in or inside the marine sediment. A small amount floats in the water column at various depths.
References
- Pseudopod. Retrieved from biologydictionary.net
- Pseudopodia. Retrieved from wikipedia.org
- Radiolaria. Retrieved from wikipedia.org
- Foraminifera. Retrieved from wikipedia.org
- Amoebozoa. Retrieved from wikipedia.org
- Philopodia. Retrieved from wikipedia.org
- Axopodium. Retrieved from merriam-webster.com.