Volvox is a genus of colonial phytoflagellate algae. They are organisms of worldwide distribution, with about 35 species known so far. The first of these species were described in the 18th century by the renowned Dutch microscopist Antonie van Leeuwenhoek.
It is currently one of the most controversial groups of organisms on a scientific level, as some biologists consider that its definition as colonial organisms is inaccurate and that they are really multicellular individuals.
Volvox carteri. Taken and edited from: Photo courtesy of Aurora M. Nedelcu, from the Volvocales Information Project (http://www.unbf.ca/vip/index.htm)., via Wikimedia Commons.
Other researchers, for their part, suggest that organisms of the genus Volvox are unicellular, but that multicellularity, in plants, arose from colonies of this type.
characteristics
Volvox are organisms that form spherical, pseudo-spherical or ovoid, hollow and green structures. They can have sizes ranging from 0.5 to 1 mm. They are made up of colonies, which can have between 50 to 50 thousand individuals.
Each cell that makes up the colony is very similar to the flagellate cells of the genus Euglena, that is, it is biflagellate, with a defined nucleus, large chloroplasts and an eye spot. The shape of the cells can be spherical, stellate or oval.
Cells are linked to each other by bands of the cytoplasm. They present polarity, with the anterior region directed towards the internal cavity of the colony, leaving the flagella towards the outside.
Movement in Volvox species occurs due to the coordinated action of cell flagella rotating on their own axis. These species make vertical migrations in the water column during the day towards the surface looking for light.
They are freshwater habitats, common in ponds, ponds and other shallow bodies of water.
Taxonomy
The genus Volvox was first observed in 1700 by the Dutch microscopist Leeuwenhoek. In 1758, the Swedish naturalist Carl von Linné first described and illustrated the genus.
The number of species described is not clearly defined, being between 90 and 120, according to the different authors. However, only 35 species are currently considered valid.
This genus belongs to the Volvocales family, which includes colonial species. The cells are always biflagellate and the number of cells per colony can vary according to the species, being the species of the genus Volvox those that present the highest number.
The taxonomic classification of this group has been under debate. For many years, scientists have located it within the kingdom Plantae, in the group of green algae (Phyllum Chlorophyta).
However, in 1969 the botanist Robert Whittaker, in his classification of living beings, places the Volvox within the Protista Kingdom, a kingdom composed of groups of eukaryotes whose classification is complicated and whose characteristics do not agree with those of other kingdoms of eukaryotes. (Plantae, Animalia and Fungi).
This kingdom is currently considered polyphyletic by many authors.
Reproduction
References
- Volvox. In EcuRed. Recovered from ecured.cu.
- Volvox. On Wikipedia. Recovered from en.wikipedia.org.
- WoRMS Editorial Board (2019). World Register of Marine Species. Recovered from.marinespecies.org.
- Volvox Linnaeus, 1758. AlgaBase. Recovered from algaebase.org.
- CP Hickman, LS Roberts & A. Larson (2002). Integrated Principles of Zoology 11th Edition. McGRAW-HILL. 895 p.
- SM Miller (2010) (Volvox, Chlamydomonas, and the Evolution of Multicellularity. Nature Education.