Volvox Characteristics: Let us know that Volvox Characteristics. Volvox is a genus of colonial phytoflagellate algae. They have a worldwide distribution, with some 35 species known to date. The first of these species was described in the eighteenth century by the famous Dutch microscopist Antoine van Leeuwenhoek.
It is currently one of the most controversial groups of organisms in the scientific field, as some biologists believe that its definitions as colonial organisms are incorrect and that they are in fact multicellular individuals.
Other researchers, meanwhile, suggest organisms of the genus Volvox They are unicellular, but multicellularity in plants arose from such colonies.
Features
Volvox are organisms that are spherical, pseudospheric or oval structures, hollow and green in colour. Their size can range from 0.5 to 1 mm. They are made up of colonies, which can contain from 50 to 50 thousand individuals.
Each cell that forms a colony is similar to flagellated cells of the genus Euglena , that is, it is bifurcated, with a defined nucleus, large chloroplasts, and an ocular spot. The shape of the cells can be spherical, star-shaped or oval.
Cells are attached to each other through cytoplasmic bands. They present polarity, with the anterior region directed towards the internal cavity of the colony, releasing the flagella outwards.
Movement in species of Volvox is due to the coordinated action of spinning cellular flagella on their own axis. These species make vertical migrations in the water column during the day towards the surface in search of light.
They are freshwater habitats, common in ponds, ponds and other shallow bodies of water.
classification
Ling volvox It was first observed in 1700 by the Dutch microscopist Leeuwenhoek. In 1758, the Swedish naturalist Karl von Linn first described and depicted the style.
According to various authors, the number of species described is between 90 and 120 not clearly defined. However, currently only 35 species are considered valid.
This genus belongs to the Volkovales family, which includes colonial species. The cells are always bifurcated and the number of cells per colony can vary by species, with the species of the genus Volvox with the greatest number.
The taxonomic classification of this group is under debate. For many years, scientists have placed it within the plant kingdom, a group of green algae (Phyllum chloride).
However, in 1969 the botanist Robert Whitaker, in his Taxonomy of Living Animals, located Volvox within the Kingdom Protista, a kingdom composed of groups of eukaryotes whose taxonomy is complex and whose characteristics belong to other kingdoms of eukaryotes (Plantae, Animalia and Fungi). ) does not match.
This kingdom is currently considered polyphyletic by many authors.
Reproduction
There are two types of Volvox breeding; asexual and sexual. Any of these types of reproduction involves all the colony-forming cells, but some cells located in the equatorial regions.
Asexual reproduction
When species of the genus Volvox reproduce asexually, they reproduce through serial or mitotic divisions of germ cells. These divisions continue until one or several daughter colonies are formed within the mother colony.
The daughter ancestor will remain inside the colony until it dies and leaves them free.
sexual reproduction
Sexual reproduction involves the production of two types of sex cells (gametes), eggs (macrogametes) and sperm (microgametes). After the sperm mature, they leave the progenitor colony to fertilize a mature ovum (in the outer periphery of the colony).
Once fertilization occurs, the zygote, which is the result of the union of the micro and macrogame, secretes a solid and spiny layer around it, and it will later become a new colony.
Asexual reproduction seems to be more frequent than sexual reproduction among volvox , as observed in laboratory tests. However, it is not known with certainty what can be the frequency of reproduction of both types in nature.
In Volvox globator, sexual reproduction occurs in the spring, followed by repeated asexual reproduction events that take place in the summer.
nutrition
Volvox They are green algae and they present chloroplasts, they obtain their food through photosynthesis. Photosynthesis is the transformation of inorganic matter into organic matter with the release of oxygen, using light energy (sunlight).
These organisms perform nocturnal migration, that is, they move vertically with daily periodicity.
During the day they are in the most superficial layers of the water to take advantage of sunlight in the photosynthetic process, but during the night they move to deeper waters to take advantage of the nutrients of these regions.
Volvox and Evolution
It was originally estimated that the Volvox they diverged from their ancestors about 35 or 50 million years ago. However, recent studies indicate that this divergence may have occurred 234 million years ago.
Scientists suggest that their ancestors were free-living microorganisms, sub-cylindrical and biflagellate.
In a tireless quest to explain the origin of multicellularity, we came to use the style of Volvox as a study source to design and propose hypotheses about the origin of multicellular organisms.
volvox They are considered the ideal group for studies on evolution, as they present relatively simple multicellularity; They present only two types of cells that do not form organs or, therefore, organ systems.
It is known, today, that multicellular organisms originated in many groups and independently on different occasions.
importance
The importance of gender volvox It is primarily ecological. These organisms produce oxygen through photosynthesis, and, like other microorganisms, are the basis of the trophic network in the environment where they live, being food for various invertebrates, especially rotifers.
In some freshwater environments, where chemical conditions suggest that eutrophication has occurred, phytoplaston populations have increased proportionately.
These population increases, called bloom or algal blooms, are harmful to fish and other invertebrates. Some species of Volvox contribute to these blooms.
In addition, they are a species of interest in evolutionary studies, as already mentioned .
