These cilia are used to create a current of water from which it sweeps food. Every little while, the stentor will close up the cilia crown and contact, bringing the food within its cell structure.
The crown is not the only cilia on the stentor, its whole body is covered with shorter cilia, which are used for locomotion when free swimming. When moving, the stentor is contracted into an oval or pear shape.
Being single celled, there are no separate parts which make up a "mouth" or other organs. For digestion, the cell wall envelops the food, and separates to form a round bubble like "vacuole" within the cell.
After the nutrition from the food is extracted, this vacuole moves to the outer cell wall and 'pops', evacuating the remaining contents. Since stentors have a cell density higher than the water in which they live, osmotic pressure causes water to transport into the cell.
The stentor cell actively collects this excess water into a vacuole, and expels it; thereby maintaining the internal fluid density. Stentors, like most ciliates, are filter feeders; passively eating whatever happens to be swept in their direction. They normally eat bacteria and algae, though large stentors are reported to opportunistically eat rotifers or anything else that they can catch. Unlike some vorticella, where the whole colony is connected as a single organism, a colony of stentors is a group of individual organisms which just happen to be located together.
This colony looked like a spot of mold beginning to form on the side of the collecting bottle. I pushed it loose with a pipette, and transferred it to a microscope slide. When two Stentor cross paths, the micronucleus replicates itself and the genetic information is exchanged. The exchanged information reorganizes and becomes a new macronuclei. Throughout the course of its life, the Stentor undergoes asexual reproduction multiple times before it is ready to sexually reproduce again.
Conjugation is a complex form of isogamy which is a form of sexual reproduction that is unique to unicellular organisms. As a unicellular organism, each and every organism is virtually identical in structure meaning that they generally cannot be classified as male or female. Regardless, fertilization takes place and gametes of two separate organisms combine to form a zygote.
Fission refers to the division of a single organism into two or more equal organisms that resemble or are identical to the parent.
This is the preferred and most common form of reproduction amongst the Stentor. As the membrane tears apart, half of the genetic material that is replicated and half of the genetic material that is original is separated. In this process, new cells are genetically identical.
Stentor are massive microorganisms and their distinctive trumpet shape makes them very easy to spot. Stentor tend to be found near large accumulations of algae. So if you are looking for Stentor make sure when you take a sample there is plenty of algae. Larger stentor can even be seen without a microscope especially when they are fully elongated. Stentor tend to move very slowly but most of the time they are anchored to microscopic debris, so it is very easy to use high magnifications to observe the minute details of these magnificent microorganisms.
Aside from being very easy to observe their cyan color makes them one of the most beautiful microorganisms on the planet in my humble opinion. The name of the Stentor comes from its trumpet shape and the herald in Greek mythology known for possessing a booming voice. The Stentor was first observed and documented in by Abraham Trembley.
Abraham Trembley was a Genevan naturalist known for his work as it related to hydra. Trembley is credited as the father of zoology. Some go as far as calling him the father of biology. Trembley thought he had discovered a new species in the hydra, but it was in fact first written about by Leeuwenhoek in The book included the most detailed drawings and explanations of the hydra.
Within this groundbreaking novel was an excerpt about a large, trumpet-shaped ciliate that was thought to have been a hydra at the time. Trembley was unwittingly describing the Stentor and mistakenly grouping it with the hydra. Lorenz Oken was a botanist, biologist, and ornithologist. He specialized in natural history and medicine. Oken was particularly fascinated by Stentor thanks to his background in medicine.
Protist Image Database, via Wikimedia Commons, public domain license. Stentor is a single-celled organism that's shaped like a trumpet when it's extended. It's interesting to observe, especially when it's catching its prey.
The organism has some impressive features. Researchers have discovered that Stentor roeselii seems to make relatively complex decisions with respect to avoiding harm. It can "change its mind" about its behavior as a dangerous stimulus continues. Understanding the biology of this process might help us understand the behavior of our cells.
Stentor is found in ponds and other bodies of still water. It's between one and two millimetres long and can be seen with the naked eye. A hand lens provides a better view.
A microscope is required in order to see details of the organism's structure and behavior. If a microscope is available, watching a living Stentor can be a very absorbing activity. Stentor is a member of the phylum Ciliophora. The organisms in this phylum are commonly known as ciliates and live in aquatic environments. They are unicellular and bear hair-like structures called cilia on at least some part of their body.
The cilia beat and move the surrounding fluid. In some organisms, they move the cell itself. Though ciliates are usually referred to as microorganisms and are studied by microbiologists, Stentor is visible without a microscope. Stentor, other ciliates, and some additional organisms are sometimes referred to as protists. Protista is the name of a biological kingdom.
It contains unicellular or unicellular-colonial organisms, including Stentor, as well as some multicellular ones The kingdom system is often used to classify organisms in schools.
Scientists prefer to use the cladistic system of biological classification. Ciliates and some other unicellular organisms are sometimes referred to as protozoa. This is an old term that comes from the Ancient Greek words proto meaning first and zoa meaning animal. The word "Stentor" is a genus name as well as a common name. Multiple species exist in the genus. In the story, Stentor had a voice as loud as fifty men.
The organism lives in bodies of fresh water such as ponds, slow-moving streams, and lakes. It spends some of its time swimming through the water and the rest attached to submerged items such as algae and debris.
When it's swimming, Stentor has an oval or a pear shape. When it's attached to an item and feeding, it has a trumpet or horn shape. Its covered by short, hair-like cilia. The edge of the trumpet opening bears much longer cilia. These beat, creating a vortex that pulls in prey. Stentor is attached to the substrate by a slightly expanded region known as the holdfast. It has the ability to contract into a ball when it's joined to a substrate.
In some individuals, a covering called a lorica surrounds the holdfast end of the cell. The lorica is mucilaginous and contains debris and material excreted by the Stentor. Stentor has organelles found in other ciliates. It contains two nuclei—a large macronucleus and a small micronucleus.
The macronucleus looks like a beaded necklace. Vacuoles sacs surrounded by membrane form as needed. Ingested food enters a food vacuole, where enzymes digest it. Stentor also has a contractile vacuole, which absorbs water that enters the organism and expels it to the outer environment when it's full.
The water is released through a temporary pore in the cell membrane. Stentor can stretch its body far beyond the substrate as it feeds. It eats bacteria, more advanced single-celled organisms, and rotifers.
Rotifers are also interesting creatures. They are multicellular, but they are smaller than many unicellular ones and much smaller than a Stentor. Stentor polymorph us and a few other species contain a single-celled green alga named Chlorella , which survives in the ciliate and performs photosynthesis. Stentor uses some of the food that the algal cells produce. The alga is protected inside the ciliate and absorbs substances that it needs from its host. The Stentor species that have been studied reproduce primarily by splitting in half, a process known as binary fission.
They also reproduce by attaching to one another and exchanging genetic material, which is known as conjugation. The video below is interesting and well worth watching. As one of the creators says in a YouTube comment, however, the commentary contains an error. Tardigrades contain eight legs, not six. Researchers are discovering that Stentor has multiple features of special interest.
Three of these features are its genetic code, its ability to regenerate, and the polyploidy in its macronucleus. Stentor primarily uses the standard genetic code, which we use.
Other ciliates whose genome has been studied have a non-standard code. The genetic code determines many of an organism's characteristics. The chemicals are called nitrogenous bases and are often represented by their initial letter. Each sequence of three nitrogenous bases has a particular meaning, which is why the code is referred to as a triplet code.
The sequence is known as a codon. Many codons contain instructions related to the manufacture of polypeptides, which are the chains of amino acids used to make protein molecules. U represents a nitrogenous base called uracil, A represents adenine, and G represents guanine. Stop codons "tell" the cell to stop adding amino acids to the polypeptide that is being made and that the chain has been completed.
In most ciliates, the codons tell the cell to add an amino acid called glutamine to the polypeptide that is being produced instead of signaling the end of the chain. Stentor is known for its amazing ability to regenerate. If its body is cut into many small pieces anywhere from 64 to segments, according to different sources , each piece can produce an entire Stentor. The piece must contain a portion of the macronucleus and the cell membrane in order to regenerate.
This is not as unlikely a condition as it may sound. The macronucleus extends through the whole length of the cell and a membrane covers the entire cell. The macronucleus exhibits polyploidy.
Human cells are diploid because they have two sets. Each of our chromosomes contains a partner bearing genes for the same characteristics.
The Stentor macronucleus contains so many copies of chromosomes or segments of chromosomes tens of thousands or higher, according to various researchers that it's highly likely that a small piece will contain the necessary genetic information to create a new individual. Scientists have also observed that a Stentor has an amazing ability to repair damage to the cell membrane.
The organism survives wounds that would most likely kill other ciliates and single-celled organisms. The cell membrane is often repaired and life appears to go on as normal for an injured Stentor, even when it has lost some of its internal contents through a wound. Stentor consists of just one cell, so many people likely have the impression that its behavior must be very simple.
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