Volvox globator
{{Short description|Species of alga}}
{{Speciesbox
| image = Volvox globator.jpg
| image_caption =
| genus = Volvox
| species = globator
| authority = L.
}}
Volvox globator is a species of green algae in the family Volvocaceae. The type species of Volvox, the name was originally given by Carl Linnaeus in his 1758 work Systema Naturae.{{AlgaeBase species|name=Volvox globator|id=27955}} In 1856 its sexuality was described by Ferdinand Cohn and is the same as Sphaeroplea annulina.http://www.pnf.org/compendium/Ferdinand_Julius_Cohn.pdf{{full citation needed|date=October 2016}} It is a freshwater alga with a cosmopolitan distribution.
Description
Volvox globator is a colony of bi-flagellated cells; mature colonies are 400–575 μm long and 380–540 μm wide. The colony consists of thousands of somatic cells arranged in a single peripheral layer embedded in a gelatinous matrix, forming a hollow sphere.{{cite journal|title=A Comparative Study of the Species of Volvox|last1=Smith|first1=G.M.|journal=Transactions of the American Microscopical Society|date=1944|volume=63|issue=4|pages=265–310|jstor=3223302|doi=10.2307/3223302}} Each cell is pyriform in side view, connected to each other by cytoplasmic strands, making them appear stellate in polar view. Each individual cell is surrounded by a gelatinous sheath. Cells have two to six contractile vacuoles, a parietal chloroplast with several minute pyrenoids, a small red stigma.{{cite book|doi=10.1017/CHOL9781108784122 |title=The Freshwater Algal Flora of the British Isles |date=2021 |last1=John |first1=David M. |last2=Whitton |first2=Brian A. |last3=Brook |first3=Alan J. |isbn=978-1-108-78412-2 |edition=2|publisher= Cambridge University Press|pages=896}} Nutrition is holophytic.{{cn|date=April 2025}}
=Reproduction=
Asexual colonies are usually filled with three to 17 (usually four to seven) gonidia irregularly distributed in the posterior of the colony. Gonidia are 10–13 μm in diameter; these divide by binary fission to become embryos. After the cells in the embryo finish dividing, they undergo colony inversion; that is, the embryo turns itself inside out, so that the flagella are correctly oriented outwards. In Volvox globator, the posterior of the embryo first pushes inwards, then the anterior pole of the embryo produces an opening (called a phialopore), allowing the embryo to invert. This method of inversion is called Type B inversion, in contrast to the more well-studied Type A inversion in Volvox carteri.{{cite journal |doi=10.1186/1741-7007-9-89 |pmid=22206406 |pmc=3324393 |title=There is more than one way to turn a spherical cellular monolayer inside out: Type B embryo inversion in Volvox globator |journal=BMC Biology |volume=9 |pages=89 |year=2011 |last1=Höhn |first1=Stephanie |last2=Hallmann |first2=Armin |doi-access=free }} Mature embryos are up to 250 μm in diameter.
Sexual reproduction is homothallic, with sexual colonies around the same size as asexual ones. Sexual colonies contain three to seven antheridial (sperm) packets and 11–72 (typically 20–30) eggs. The sperm packets are compressed globoids about 22–32 μm, and divide to form 256 antherozoids (sperm). The zygotes are round and covered with straight, blunt spines; they are 36–44 μm (with spines, 45–54 μm).
Movement
Volvox globator has been used as a model organism for a over a century, to study cellular motion. Volvox colonies tend to swim towards the direction of light.{{cite journal |doi=10.1002/cne.920170202 |title=Light reaction in lower organisms. II. Volvox globator |journal=Journal of Comparative Neurology and Psychology |volume=17 |issue=2 |pages=99–180 |year=1907 |last1=Mast |first1=S. O. |url=https://zenodo.org/record/1426767 }}
Taxonomy
As the type species of Volvox, it is placed in Volvox sect. Volvox (also known as Euvolvox). This section is characterized by having cells with thick cytoplasmic connections between each other, making the cells appear stellate, and having spiny zygotes. Within section Volvox, species are separated based on monoicy/dioicy, number of eggs and sperm packets per spheroid, and zygote morphology.{{cite journal|doi=10.1111/j.1529-8817.2012.01142.x |title=Description of two new monoecious species of Volvox sect. Volvox (Volvocaceae, Chlorophyceae), based on comparative morphology and molecular phylogeny of cultured material |date=2012 |last1=Isaka |first1=Nanako |last2=Kawai-Toyooka |first2=Hiroko |last3=Matsuzaki |first3=Ryo |last4=Nakada |first4=Takashi |last5=Nozaki |first5=Hisayoshi |journal=Journal of Phycology |volume=48 |issue=3 |pages=759–767 |pmid=27011093 |bibcode=2012JPcgy..48..759I }}
References
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Further reading
- {{cite journal |doi=10.1002/jez.1400270304 |title=Reversion in the sense of orientation to light in the colonial forms, Volvox globator and Pandorina morum |journal=Journal of Experimental Zoology |volume=27 |issue=3 |pages=367–90 |year=1919 |last1=Mast |first1=S. O. |bibcode=1919JEZ....27..367M |url=https://books.google.com/books?id=W8_RAAAAMAAJ&pg=PA367 }}
- {{cite journal |doi=10.1007/BF00340895 |title=The rate of adaptation to light and to darkness in Volvox globator |journal=Zeitschrift für Vergleichende Physiologie |volume=17 |issue=3 |pages=644–58 |year=1932 |last1=Mast |first1=S. O. }}
- {{cite journal |doi=10.1007/BF01560949 |title=Die ungeschlechtliche Entwicklung von Volvox |trans-title=Asexual development of Volvox |language=German |journal=Die Naturwissenschaften |volume=13 |issue=19 |pages=397–402 |year=1925 |last1=Zimmermann |first1=Walter |bibcode=1925NW.....13..397Z |s2cid=46116067 }}
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Category:Plants described in 1758