Stentor It is a group of protists that are distinguished from the others by their characteristic trumpet shape. Likewise, they are considered among the largest protists, and can even be seen with the naked eye.
They were first described by the German naturalist Lorenz Oken in 1815. This genus encompasses a total of 20 species, of which one of the best known is Stentor coeruleus. Although they have been sufficiently studied, there are still many aspects of its biology that remain hidden from science.
In their structure they are similar to other organisms of this kingdom. However, they present some innovations like a primitive mouth. This has allowed them to expand their diet, as they not only feed on bacteria, but species have even been known to feed on small rotifers..
Similarly, individuals in this group have the ability to vary their shape when they feel threatened. In these cases, they retract their body and transform into a spherical structure, protecting everything that is inside..
This is a group of species that still need to be studied in greater detail in order to elucidate with more precision their characteristics and living conditions..
The taxonomic classification of the genus Stentor is as follows.
Super sharp: Alveolata
The body of organisms belonging to the genus Stentor is shaped like a trumpet or horn. This is its most representative characteristic. Likewise, the body is covered by cilia, which have a double function: to help the individual move (swim) and sweep food away so that the body can ingest it..
With regard to their appearance, various species belonging to this genus manifest different colors. Such is the case of Stentor coeruleus, which shows a blue coloration.
At the microscopic level, it can be seen that each individual has a macronucleus, generally spherical in shape, accompanied by several micronuclei. Like many unicellular living beings, those of the Stentor genus have a contractile-type vacuole that helps maintain osmotic pressure.
In terms of size, it varies from one species to another. They are part of the largest single-celled organisms, even reaching several millimeters in length.
Individuals of this genus fall into the category of eukaryotic organisms. This means that their cells have a cell membrane, a nucleus and a cytoplasm in which various organelles are scattered..
As for his lifestyle, he is sedentary. Organisms of the genus Stentor tend to attach to the substrate through the narrowest part of their bodies..
Sometimes they can live with certain chlorophyta algae under a symbiotic relationship. It is important to remember that in this type of interspecific relationship, two individuals of different species coexist together, needing each other to survive..
In this case, the algae are ingested by the Stentor. Inside the body it feeds on the waste produced in the nutrition process, while the Stentor takes advantage of the nutrients that the algae synthesizes.
To move through the aquatic environment, members of this genus use the numerous cilia that surround their body, which serve as a driving organ through the water.
Individuals of the genus Stentor are found in bodies of water. They have a preference for fresh water, but not for sea water. Likewise, they are not present in all bodies of fresh water, but are found in those in which the water remains static or stagnant, such as lakes..
They are not found in flowing bodies of water, such as rivers. The answer to this may be found in the food preferences of these organisms. Bacteria are the main food in their diet, especially those involved in the decomposition and degradation of dead organic matter..
In rivers, streams and streams, their natural course would carry any residue, so in them, members of the genus Stentor they would not find nutrient availability.
The Stentor mainly feeds on bacteria and small microscopic organisms that float freely in the water. In its structure, it presents a primitive mouth known as an oral bag, through which food enters the body of the individual..
The cilia that are located near it move rhythmically in order to bring the possible food particles closer together.
Once this happens, the digestive vacuole begins to exert its function, which contains enzymes that are responsible for degrading and fragmenting nutrients to make them more assimilable..
Later, as in any digestive process, some residues remain, which are expelled out of the Stentor with the help of the contractile vacuole. Ingested nutrients are used for energy-generating processes.
How in the vast majority of the organisms of the Protista Kingdom, those of the genus Stentor they reproduce through asexual mechanisms. The distinctive feature of this type of reproduction is that the descendants are exactly the same as the parent that originated them..
The specific process by which members of the genus reproduce Stentor it is known by the name of binary fission. In this, the parent is divided into two equal individuals.
The first step necessary for binary fission to occur is DNA duplication. This is necessary because each new individual must receive the full genetic load of the parent..
Once the DNA has been duplicated through the process of mitosis, both copies of the resulting genetic material move to opposite poles of the cell. Immediately the individual's body begins to experience longitudinal segmentation.
Finally, the cytoplasm and the cell membrane culminate their division, thus originating two individuals exactly equal to each other and to the parent..
As might be expected, this type of reproduction is not very advantageous for the organisms that have it, since since there is no genetic variability, these species could not survive in the face of adverse changes in environmental conditions. Herein lies the great disadvantage of asexual reproduction.
Similarly, a type of sexual reproduction has been described among organisms of this genus. The specific process by which this occurs is known as conjugation.
In order to understand this process, it is important to know that within these individuals there are two important structures: the macro-nucleus and the micro-nucleus. The micronucleus is the DNA that the two organisms will exchange when they mate.
This process in Stentor It occurs in the following way: when two organisms of this genus meet, they can hook up for reproductive purposes. After the exchange of micronuclei has taken place, they reorganize, make copies and transform into macronuclei.
Later, in the course of time, each will undergo numerous divisions by asexual reproduction (binary fission), at the end of which it will be ready again for another mating..
Individuals belonging to the genus Stentor They are primitive, therefore they do not have specialized structures for capturing oxygen from the environment. Taking this into account, they must then resort to extremely simple processes to cover their needs for this element..
The process that these organisms use to obtain oxygen is direct respiration, through diffusion. Oxygen is able to cross its cell membrane, following the concentration gradient. That is, from where it is most concentrated to where it is least concentrated..
This is how it manages to enter the cell to be used in various metabolic processes. Once this has happened, another gas is generated, carbon dioxide (COtwo), which is highly toxic to the cell, so it must be expelled out of it.
Once again, making use of simple diffusion, the cell releases it to the external environment, through the membrane..