A pseudopodium or pseudopod plural: pseudopodia or pseudopods is a temporary cytoplasmic extension of an amoeboid cell, used for locomotion and ingestion of food. Pseudopodia are powered by microfilaments near the cellular membrane. About half of the internal space of an amoeba contains microfilaments. A pseudopodium contains both granuloplasm and hyaloplasm. Pseudopodia which only contain hyaloplasm are called subpseudopodia. Form and structure of the pseudopodia are important taxonomical characters.
Depending upon their shape, several types of pseudopodia are distinguished, e. Shell colorless to amber-colored, rough surface, few. Lacogromia sp. I found this species in a sample from a small pond in the moor of Cayan near Pont. The original description with original drawings, Penard, Rhizaspis spinosa Penard, Dumack et al.
It differs. For such organisms as members of the class Actinopoda , axopodia play an important role in feeding. As already mentioned, axopodia have a sticky substance on their surface that is produced by mucocysts. In addition, they also possess kinetocysts that eject thread-like structures that effectively trap their prey. Using these extrusomes, these organisms are able to trap food material or prey which are then transported to the cell body through the cytoplasmic stream.
While smaller prey can be trapped and captured by a single axopodiaum, larger ones are entangled in several axopodia. In some cases, several individuals have been shown to participate in trapping larger prey. Apart from feeding, axopodia have also been shown to help maintain protists in position in water and even contribute to locomotion.
For instance, through a controlled change in length of axopods, a number of heliozoa have been shown effectively transverse in aquatic environments. This, in other organisms, is achieved through the expansion and contraction of ectoplasmic vacuoles located between the axopodia. Here, the organism is able to remain in position or control the direction to which they seek to move.
During cell division , both the axopodia and ectoplasm are lost causing the organism to sink to the bottom. Some of the other notable functions of axopodia include:. Also referred to as rhizopodia or extrathalamous cytoplasm in some books, reticulopodia are thread-like pseudopodia that branch and fuse to form a network that is extremely dynamic. As is the case with axopodia, reticulopodia are also composed of tubules and the cytoplasm.
They can be found in a number of organisms including Endomyxa amoebae and some foraminiferans an ancient group of protists. In these organisms, reticulopodia are involved in feeding and locomotion. Like axopodia, reticulopodia are also composed of microtubules and cytoplasm.
Here, microtubules that make up the pseudopods consist of a unique type of tubulin known as Type 2 beta-tubulin. This tubulin forms helical filaments HFs which is the basis for the microtubule found in foraminiferan reticulopodia. In foraminiferans and other organisms, the retuculopodia extrude through one or more pores apertual openings.
Initially, these pseudopods may be thin and pointed similar to filopodia in appearance. As the amount of cytoplasm in the structure increases, the pseudopodial trunk, known as peduncle, becomes thicker and branches to form new pseudopods. While these pseudopods grow and anastomose link together , they form a network that resembles web-like threads. Some of the main characteristics of reticulopodia include:. This means that the cytoplasm streams along the lengths of the pseudopods to and from the cell body.
Like axopodia, reticulopodia play an important role in feeding and locomotion. However, their primary function is in food gathering and feeding. During feeding, the organism spreads the pseudopods which looks like an irregular web which scour their immediate surfaces and gather available food material to be ingested. Prey may include such single-celled organisms as bacteria that are trapped in the web and taken into the food vacuoles for digestion.
Apart from feeding, reticulopodia are also used for locomotion. However, this is not their primary function. Lopodium is the most common type found in such organisms as Amoeba proteus. Lobopods are characterized by finger-like tubular pseudopodia consisting of ecto and endoplasm. However, they have also been shown to contain actin and myosin microfilaments which contribute to the overall movement.
Unlike the other pseudopods, microtubules in lobopodia are poorly developed. In many amoebas, lobopodia are primarily involved in locomotion. In such organisms, the formation of lobopodia is influenced by chemical signals in their environment.
In the presence of a food substance, chemical signals influence the direction to which the amoeba moves. Here, the molecules from the food material bind to the receptors located on the organism's cell membrane which stimulates the formation of filaments through the aggregation of globular actin. With the addition of globular actin, the structure filament continues to elongate which in turn causes a protrusion of the membrane this action results in pseudopodia formation. Surface area to volume ratio of cells.
Surface area of a box cuboid. Next lesson. Current timeTotal duration Google Classroom Facebook Twitter. Video transcript - [Instructor] The goal of this video is to appreciate some of the structures that you see even in unicellular organisms. So this right over here is a picture of the amoeba Chaos carolinense. And what you see here is a projection coming off from the main part of the cell, and this is called a pseudopod, which is referring to it being a false foot.
The pod is coming from the same root word as podiatry, which is referring to the foot. And what I really want you to appreciate, this is used by amoeba either to move around or it could be even used to attack something that it wants to engulf. And think about what it might take to be able to do this, to be able to grow this type of a pseudo foot, this type of a false foot. You need all sorts of microstructures in here that will extend or contract as necessary. And think about the machinery that you need to do that.
And so the key realization is, sometimes we just imagine cells as these bags of fluid with a few things floating around. But they're these incredibly complex structures, and biologists even today don't fully understand how everything works and they're studying how these things actually come to be. Now another structure that you'll often see in unicellular organisms that either help them move around or even help move other things around are cilia.
So this right over here is a picture of Oxytricha trifallax, which is a unicellular organism. It's a eukaryote. And you can clearly see these projections from its body here, these hairlike structures.
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