Editing Volvox

{{Short description|Genus of algae}}
{{Automatic taxobox
| image = Mikrofoto.de-volvox-4.jpg
| image_caption = ''Volvox'' sp.
| taxon = Volvox
| authority = [[Carl Linnaeus|L.]]
| type_species = Volvox globator
| type_species_authority = L.<ref name=AlgaeBase>{{AlgaeBase genus | id=43497 | title=''Volvox'' Linnaeus, 1758 | access-date=2025-04-12 }}</ref>
| synonyms_ref = <ref name=Smith1944/>
| synonyms = 
*''Besseyosphaera'' {{au|W.R.Shaw}}
*''Campbellosphaera'' {{au|W.R.Shaw}}
*''Copelandosphaera'' {{au|W.R.Shaw}}
*''Janetosphaera'' {{au|W.R.Shaw}}
*''Merrillosphaera'' {{au|W.R.Shaw}}
*''Sphaerosira'' {{au|Ehrenberg}}
| subdivision_ranks = Sections
| subdivision = See {{Section link||Taxonomy}}
}}

'''''Volvox''''' is a [[Polyphyly|polyphyletic]] [[genus]] of [[chlorophyte]] [[green algae]] in the family [[Volvocaceae]]. ''Volvox'' species form spherical [[colony (biology)|colonies]] of up to 50,000 cells, and for this reason they are sometimes called '''globe algae'''. First reported by [[Antonie van Leeuwenhoek]] in 1700, it is distinctive and easily identified in the [[microscope]]. It occurs in variety of [[freshwater]] habitats, and has a widespread, [[cosmopolitan distribution]].<ref name=Smith1944/>

''Volvox'' diverged from unicellular ancestors approximately {{Ma|200}}.<ref name="daily">{{cite web |author=University of Arizona |date=February 22, 2009 |title=Single-celled algae took the leap to multicellularity 200 million years ago |website=[[Science Daily]] |url=https://www.sciencedaily.com/releases/2009/02/090219140546.htm}}</ref> Colonies of ''Volvox'' are differentiated into [[somatic cell|somatic]] and reproductive cells, and are capable of both sexual and asexual [[reproduction]]. Additionally, its close relatives are diverse in body plan and reproductive strategy, ranging from unicellular organisms such as ''[[Chlamydomonas]]'' to simple colonial organisms such as ''[[Pandorina]]'' and ''[[Eudorina]]''. Because of this, ''Volvox'' and its relatives are used as [[model organism]]s in the classroom and laboratory to study biological processes such as cellular movement, [[sexual reproduction]], and evolution of [[multicellularity]].<ref name=Herron>{{Cite journal |last=Herron |first=Matthew D. |date=2016 |title=Origins of multicellular complexity: ''Volvox'' and the volvocine algae |journal=Molecular Ecology |volume=25 |issue=6 |pages=1213–1223 |doi=10.1111/mec.13551 |pmc=5765864 |pmid=26822195|bibcode=2016MolEc..25.1213H }}</ref>

== History of knowledge ==
Antonie van Leeuwenhoek first reported observations of ''Volvox'' in 1700.<ref name="Leeuwenhoek">{{cite journal |last=van Leeuwenhoek |first=Antonie |author-link=Antonie van Leeuwenhoek |date=1700 |title=Part of a Letter from Mr Antony van Leeuwenhoek, concerning the Worms in Sheeps Livers, Gnats, and Animalcula in the Excrements of Frogs |journal=[[Philosophical Transactions of the Royal Society]] |doi=10.1098/rstl.1700.0013 |volume=22 |issue=260–276 |pages=509–518 |bibcode=1700RSPT...22..509V |doi-access=free}}</ref><ref>Herron, M. (2015). "...of the bignefs of a great corn of fand...". ''Fierce Roller Blog'', [http://www.fierceroller.com/?p=341] {{Webarchive|url=https://web.archive.org/web/20160603015243/http://www.fierceroller.com/?p=341|date=2016-06-03}}.</ref> After some drawings and a fuller description by [[Henry Baker (naturalist)|Henry Baker]] in 1753,<ref>Baker, H. (1753). ''Employment for the microscope''. R. Dodsley: London, pl. XII, f. 27, [https://www.biodiversitylibrary.org/bibliography/45920].</ref> [[Carl Linnaeus]] named the genus in his 1758 work ''[[Systema Naturae]]'';<ref>Linnaeus, C. (1758). ''[[Systema naturae]] per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis''. Tomus I. Editio decima, reformata. Editio decima revisa. Vol. 1 pp. [i-iv], [1]-823. Holmiae [Stockholm]: impensis direct. Laurentii Salvii.</ref> Linnaeus named the genus ''Volvox'', with two species: ''[[Volvox globator|V. globator]]'' and ''V. chaos''. The name comes from the Latin term ''volvere'', meaning "to roll", and -''ox'', meaning "fierce".<ref>{{cite journal|doi=10.1016/j.cub.2004.07.034 |title=Volvox |date=2004 |last1=Kirk |first1=David L. |journal=Current Biology |volume=14 |issue=15 |pages=R599–R600 |pmid=15296767 |bibcode=2004CBio...14.R599K }}</ref> ''Volvox chaos'' is an [[amoeba]] now known as ''[[Chaos (genus)|Chaos]]'' sp.<ref>Herron, M. (2016). Moving without limbs! Linnaeus on Volvox. ''Fierce Roller Blog'', [http://www.fierceroller.com/?p=773] {{Webarchive|url=https://web.archive.org/web/20160603053127/http://www.fierceroller.com/?p=773|date=2016-06-03}}.</ref><ref>Spencer, M.A., Irvine, L.M. & Jarvis, C.E. (2009). Typification of Linnaean names relevant to algal nomenclature. ''Taxon'' 58: 237-260, [http://images.algaebase.org/algaebase/pdf/5964B937079ef2A1D4lrS280C31A/45005.pdf] {{Webarchive|url=https://web.archive.org/web/20160508170536/http://images.algaebase.org/algaebase/pdf/5964B937079ef2A1D4lrS280C31A/45005.pdf|date=2016-05-08}}.</ref>

Linnaeus' description of ''Volvox globator'' was vague enough that it could apply to any of the currently accepted species of ''Volvox''. The current [[circumscription (taxonomy)|circumscription]] of ''V. globator'' is based on [[Christian Gottfried Ehrenberg]]'s descriptions; however, he mistakenly thought the asexual and sexual colonies of ''Volvox'' were different species, and placed the male colonies in a separate genus, ''Sphaerosira''. This confusion was cleared up by [[Samuel Friedrich Stein]] in 1878.<ref name=Smith1944>{{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}}</ref>

In the twentieth century, [[Walter Robert Shaw|W. R. Shaw]] added several species to ''Volvox'', but also split off many species into several genera, namely ''Besseyosphaera'', ''Campbellosphaera'', ''Merrillosphaera'', ''Copelandosphaera'', and ''Janetosphaera''. Although most systematists did not accept these genera, they did accept them as [[section (biology)|section]]s within the genus ''Volvox''; [[Gilbert Morgan Smith]] reduced this to four sections in total.<ref name=Smith1944/> More recently, phylogenetic studies revealed that ''Volvox'' was polyphyletic, consisting of several clades which partially aligned with the sections as defined by Smith.<ref>{{cite journal|doi=10.1111/j.1529-8817.2009.00803.x |title=Evolution of developmental programs in ''Volvox'' (Chlorophyta) |date=2010 |last1=Herron |first1=Matthew D. |last2=Desnitskiy |first2=Alexey G. |last3=Michod |first3=Richard E. |journal=Journal of Phycology |volume=46 |issue=2 |pages=316–324 }}</ref> Therefore, in 2015 [[Hisayoshi Nozaki]] and colleagues emended the sections.<ref name=Nozaki2015>{{cite journal|doi= 10.1371/journal.pone.0142632 |doi-access= free |title= Delineating a New Heterothallic Species of Volvox (Volvocaceae, Chlorophyceae) Using New Strains of "Volvox africanus" |date= 2015 |last1= Nozaki |first1= Hisayoshi |last2= Matsuzaki |first2= Ryo |last3= Yamamoto |first3= Kayoko |last4= Kawachi |first4= Masanobu |last5= Takahashi |first5= Fumio |journal= PLOS ONE |volume= 10 |issue= 11 |pages= e0142632 |bibcode= 2015PLoSO..1042632N |pmc= 4643018 }}</ref>

== Description ==
[[File:Volvox.svg|thumb|''Volvox'' colony: 1) ''[[Chlamydomonas]]''-like cell, 2) Daughter colony, 3) Cytoplasmic bridges, 4) Intercellular gel, 5) Reproductive cell, 6) Somatic cell.]]
Mature colonies of ''Volvox'' [[colony (biology)|colony]] are composed of hundreds, up to tens thousands of cells from two differentiated cell types: numerous [[flagellate]] [[Somatic (biology)|somatic cells]] and a smaller number of [[germ cell]]s lacking in soma that are embedded in the surface of a hollow sphere or [[Coenobium (morphology)|coenobium]] containing an [[extracellular matrix]]<ref name="daily" /> made of [[glycoprotein]]s.<ref name="Hallmann">{{cite book |last=Hallmann |first=A. |date=2003 |title=Extracellular matrix and sex-inducing pheromone in ''Volvox'' |series=International Review of Cytology |doi=10.1016/S0074-7696(03)01009-X |pmid=14518551 |isbn=978-0-12-364631-6 |volume=227 |pages=131–182 |chapter=Extracellular Matrix and Sex-Inducing Pheromone in Volvox}}</ref>

Adult [[somatic cell]]s comprise a single layer with the flagella facing outward, forming a hollow spheroid. The cells swim in a coordinated fashion, with distinct anterior and posterior poles. Each cell is enclosed in a gelatinous sheath, which is either distinct or confluent depending on the species. Cells are ovoid, spherical, or star-shaped, each with two equal [[flagella]]. The cells have a cup-shaped [[chloroplast]] with a single [[pyrenoid]] and an anterior [[eyespot apparatus|eyespot]]<ref name=Nakada2014>{{cite book |editor-first1=John D.|editor-last1=Wehr|editor-first2=Robert G.|editor-last2=Sheath|editor-first3=J. Patrick|editor-last3=Kociolek |date= 2014 |edition=2 |title= Freshwater Algae of North America: Ecology and Classification |last1= Nakada|first1=Takashi| last2=Nozaki |first2=Hisayoshi |chapter= Chapter 6. Flagellate Green Algae |url= |location= |publisher= Elsevier Inc. |pages=265–313|isbn=978-0-12-385876-4 }}</ref> that enables the colony to swim toward light. The cells of colonies in the more basal ''[[Euvolvox]]'' clade are interconnected by thin strands of [[cytoplasm]], called protoplasmates.<ref>{{cite journal |last1=Ikushima |first1=N. |last2=Maruyama |first2=S. |date=1968 |title=The protoplasmic connection in ''Volvox'' |journal=[[Journal of Eukaryotic Microbiology]] |doi=10.1111/j.1550-7408.1968.tb02098.x |volume=15 |issue=1 |pages=136–140}}</ref> Cell number is specified during development and is dependent on the number of rounds of division.<ref name="Kirk">{{cite book |last=Kirk |first=David L. |date=1998 |title=''Volvox'': A Search for the Molecular and Genetic Origins of Multicellularity and Cellular Differentiation |publisher=[[Cambridge University Press]] |isbn=978-0-521-45207-6}}</ref>

=== Reproduction ===

''Volvox'' is facultatively sexual and can reproduce both sexually and asexually. In the lab, asexual reproduction is most commonly observed; the relative frequencies of sexual and asexual reproduction in the wild is unknown. The switch from asexual to sexual reproduction can be triggered by environmental conditions<ref name="pmid14667362" /> and by the production of a sex-inducing pheromone.<ref>{{Cite journal |last=Hallmann |first=Armin |year=2003 |title=Extracellular Matrix and Sex-Inducing Pheromone in Volvox |journal=International Review of Cytology |volume=227 |pages=131–182 |doi=10.1016/S0074-7696(03)01009-X |pmid=14518551 |isbn=978-0-12-364631-6}}</ref> Desiccation-resistant diploid [[zygote]]s are produced following successful fertilization.

An [[asexual reproduction|asexual]] colony includes both somatic (vegetative) cells, which do not reproduce, and large, non-motile ''[[Gonidium|gonidia]]'' in the interior, which produce new colonies asexually through repeated division. In [[sexual reproduction]] two types of [[gamete]]s are produced. ''Volvox'' species can be [[monoecious]] or [[dioecious]]. [[Male]] colonies release numerous sperm packets, while in female colonies single cells enlarge to become oogametes, or eggs.<ref name="Kirk" /><ref name="Powers">{{cite journal |last=Powers |first=J. H. |date=1908 |title=Further studies in ''Volvox'', with descriptions of three new species |journal=[[Transactions of the American Microscopical Society]] |doi=10.2307/3220908 |jstor=3220908 |volume=28 |pages=141–175}}</ref>

Kirk and Kirk<ref name="pmid3941891">{{cite journal |last1=DL |first1=Kirk |last2=Kirk |first2=MM |date=1986 |title=Heat shock elicits production of sexual inducer in Volvox |journal=Science |pmid=3941891 |doi=10.1126/science.3941891 |volume=231 |issue=4733 |pages=51–4 |bibcode=1986Sci...231...51K}}</ref> showed that sex-inducing pheromone production can be triggered in [[somatic cell]]s by a short [[heat shock]] given to asexually growing organisms. The induction of sex by heat shock is mediated by [[oxidative stress]] that likely also causes oxidative DNA damage.<ref name="pmid14667362">{{cite journal |last1=Nedelcu |first1=AM |last2=Michod |first2=RE |date=2003 |title=Sex as a response to oxidative stress: the effect of antioxidants on sexual induction in a facultatively sexual lineage |journal=Proc. Biol. Sci. |pmid=14667362 |pmc=1809951 |doi=10.1098/rsbl.2003.0062 |volume=270 |issue=Suppl 2 |pages=S136–9}}</ref><ref name="pmid15306305">{{cite journal |last1=Nedelcu |first1=AM |last2=Marcu |first2=O |last3=Michod |first3=RE |date=2004 |title=Sex as a response to oxidative stress: a twofold increase in cellular reactive oxygen species activates sex genes |journal=Proc. Biol. Sci. |pmid=15306305 |pmc=1691771 |doi=10.1098/rspb.2004.2747 |volume=271 |issue=1548 |pages=1591–6}}</ref> It has been suggested that switching to the sexual pathway is the key to surviving environmental stresses that include heat and [[drought]].<ref name="Amon">{{cite journal |last1=Amon |first1=P |last2=Haas |first2=E |last3=Sumper |first3=M |date=1998 |title=The sex-inducing pheromone and wounding trigger the same set of genes in the multicellular green alga Volvox |journal=Plant Cell |pmid=9596636 |pmc=144025 |doi=10.2307/3870664 |volume=10 |issue=5 |pages=781–9 |jstor=3870664}}</ref> Consistent with this idea, the induction of sex involves a [[signal transduction]] pathway that is also induced in ''Volvox'' by wounding.<ref name="Amon" />

=== Colony inversion ===
Colony inversion is a special characteristic during development in the order Volvocaceae that results in new colonies having their [[flagella]] facing outwards. During this process the asexual reproductive cells (gonidia) first undergo successive cell divisions to form a concave-to-cup-shaped embryo or plakea composed of a single cell layer. Immediately after, the cell layer is inside out compared with the adult configuration—the apical ends of the embryo protoplasts from which flagella are formed, are oriented toward the interior of the plakea. Then the embryo undergoes inversion, during which the cell layer inverts to form a spheroidal daughter colony with the apical ends and flagella of daughter protoplasts positioned outside. This process enables appropriate locomotion of spheroidal colonies of the Volvocaceae. The mechanism of inversion has been investigated extensively at the cellular and molecular levels using the model species, ''[[Volvox carteri]]''.<ref name="Yamashita">{{cite journal |last1=Yamashita |first1=S |last2=Arakaki |first2=Y |last3=Kawai-Toyooka |first3=H |last4=Noga |first4=A |last5=Hirono |first5=M |last6=Nozaki |first6=H |date=Nov 2016 |title=Alternative evolution of a spheroidal colony in volvocine algae: developmentalanalysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta) |journal=BMC Evol. Biol. |volume=16 |issue=1 |page=243 |pmid=27829356 |doi=10.1186/s12862-016-0794-x |pmc=5103382 |doi-access=free }} [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref> Another species ''[[Volvox globator]]'' has a similar mode of colony inversion, but begins at the posterior instead of the anterior.<ref name=Herron/>

[[File:Inversion Process for Volvox.png|899x899px|thumb|center|Embryonic inversion in ''Volvox''. (a) Adult ''V. globator'' spheroid containing multiple embryos. (b) Embryo undergoing type-A inversion (e.g., ''V. carteri''). (c) Embryo undergoing type-B inversion (e.g., ''V. globator'', ''V. aureus''). (d) Light micrograph shows semi-thin section of V. globator embryo exhibiting different cell shapes. (e) Schematic representation of cells in region marked in (d). PC: paddle-shaped cells, two different views illustrate anisotropic shape; SC: spindle-shaped cells; red line:  position of cytoplasmic bridges (CB). (f) 3D renderings of a single ''V. globator'' embryo in three successive stages of inversion. (g) Optical midsagittal cross sections of embryo in (f). (h) Traced cell sheet contours overlaid on sections in (g), with color-coded curvature κ. (i) Surfaces of revolution computed from averaged contours.<ref>Stephanie Höhn, Aurelia R. Honerkamp-Smith, Pierre A. Haas, Philipp Khuc Trong, and Raymond E. Goldstein
Phys. Rev. Lett. 114, 178101 – Published 27 April 2015. [[File:CC-BY icon.svg|50px]] This article contains quotations from this source, which is available under the [https://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 (CC BY 3.0)] license.</ref>]]

== Habitats ==
''Volvox'' is a genus of freshwater algae found in ponds and ditches, even in shallow puddles.<ref name="Powers" /> According to [[Charles Joseph Chamberlain]],<ref>{{cite book |last=Chamberlain |first=Charles Joseph |author-link=Charles Joseph Chamberlain |date=2007 |orig-year=1932 |title=Methods in Plant Histology |chapter=Chlorophyceae |publisher=Read Books |isbn=978-1-4086-2795-2 |pages=162–180 |chapter-url=https://books.google.com/books?id=O85ZudgVASEC&pg=PA165}}</ref>
<blockquote>"The most favorable place to look for it is in the deeper ponds, [[lagoon]]s, and ditches which receive an abundance of rain water. It has been said that where you find ''[[Lemna]]'', you are likely to find ''Volvox''; and it is true that such water is favorable, but the shading is unfavorable. Look where you find ''[[Sphagnum]]'', ''[[Vaucheria]]'', ''[[Alisma]]'', ''[[Equisetum fluviatile]]'', ''[[Utricularia]]'', ''[[Typha]]'', and ''[[Chara (alga)|Chara]]''. Dr. Nieuwland reports that ''[[Pandorina]]'', ''[[Eudorina]]'' and ''[[Gonium]]'' are commonly found as constituents of the green scum on wallows in fields where pigs are kept. The flagellate, ''[[Euglena]]'', is often associated with these forms."</blockquote>

== Taxonomy ==
''Volvox'' is divided into four sections, which differ from each other by the morphology of their somatic cells, asexual spheroids and zygotes:<ref name=Smith1944/><ref name=Nozaki2015/>

* ''Volvox'' sect. ''Volvox'' — Cells have coarse cytoplasmic connections between each other and are therefore stellate in polar view. The gonidia are relatively small, less than 15 μm in diameter, and are differentiated late in the development of the colony. Zygotes have spiny walls.<ref name=Smith1944/>
* ''Volvox'' sect. ''Besseyosphaera'' — Cells have no cytoplasmic connections between each other and are circular in polar view. Asexual spheroids have more than 20 gonidia. Zygotes lack spiny walls.<ref name=Smith1944/><ref name=Nozaki2015/>
* ''Volvox'' sect. ''Merrillosphaera'' (synonyms: sect. ''Campbellosphaera'', sect. ''Copelandosphaera'') — Cells have delicate cytoplasmic connections (or no connections) between each other, and are circular in polar view. Asexual spheroids have less than 20 gonidia. Zygotes lack spiny walls.<ref name=Smith1944/><ref name=Nozaki2015/>
* ''Volvox'' sect. ''Janetosphaera'' — Cells have delicate cytoplasmic connections between each other, and are circular in polar view. They lack distinct gelatinous sheaths surrounding individual cells, instead having a colonial matrix where individual sheaths are fused together. Gelatinous strands also radiate from the center to the inner surface of the colonial matrix.<ref name=Smith1944/>

In practice gelatinous sheaths and delicate cytoplasmic connections are difficult to observe, and are only reliably visible after staining with a dye such as [[methylene blue]].<ref name=Smith1944/>

=== Species ===
''Volvox'' contains the following species, according to [[AlgaeBase]].<ref name=AlgaeBase/> In addition to these accepted species, there a number of dubious "species" described under the genus ''Volvox'' which are amoebae, and/or otherwise do not belong to the current definition of ''Volvox''.<ref>{{cite journal|title=On the life-history of a soil amoeba|last1=Wilson|first1=C.W.|journal=University of California Publications in Zoology|volume=16|issue=16|pages=241–292|date=1916}}</ref>

{{div col|colwidth=30em}}
'''''Volvox'' sect. ''Besseyosphaera'''''<ref name=Nozaki2015/>
*''[[Volvox gigas]]''
*''[[Volvox powersii]]''

'''''Volvox'' sect. ''Janetosphaera'''''<ref name=Nozaki2015/>
*''[[Volvox aureus]]''
*''[[Volvox pocockiae]]''

'''''Volvox'' sect. ''Merrillosphaera'''''<ref name=Nozaki2015/>
*''[[Volvox africanus]]''
*''[[Volvox carteri]]''
*''[[Volvox dissipatrix]]''
*''[[Volvox obversus]]''
*''[[Volvox ovalis]]''
*''[[Volvox reticuliferus]]''
*''[[Volvox spermatosphaera]]''
*''[[Volvox tertius]]''
*''[[Volvox zeikusii]]''<ref>{{cite journal|doi=10.1080/00318884.2018.1540238 |title=Morphology, reproduction and taxonomy of ''Volvox dissipatrix'' (Chlorophyceae) from Thailand, with a description of ''Volvox zeikusii'' sp. nov.'' |date=2019 |last1=Nozaki |first1=Hisayoshi |last2=Takusagawa |first2=Mari |last3=Matsuzaki |first3=Ryo |last4=Misumi |first4=Osami |last5=Mahakham |first5=Wuttipong |last6=Kawachi |first6=Masanobu |journal=Phycologia |volume=58 |issue=2 |pages=192–199 |bibcode=2019Phyco..58..192N }}</ref><ref group=note>Closely related to ''V. dissipatrix''.</ref>

'''''Volvox'' sect. ''Volvox'''''<ref name=Nozaki2015/>
*''[[Volvox amboensis]]''
*''[[Volvox biwakoensis]]''<ref name=Nozaki2024>{{cite journal|doi=10.1371/journal.pone.0310549|doi-access=free |title=Two species of the green algae ''Volvox'' sect. ''Volvox'' from the Japanese ancient lake, Lake Biwa |date=2024 |last1=Nozaki |first1=Hisayoshi |last2=Matsuzaki |first2=Ryo |last3=Shimotori |first3=Koichi |last4=Ueki |first4=Noriko |last5=Heman |first5=Wirawan |last6=Mahakham |first6=Wuttipong |last7=Yamaguchi |first7=Haruyo |last8=Tanabe |first8=Yuuhiko |last9=Kawachi |first9=Masanobu |journal=PLOS ONE |volume=19 |issue=9 |pages=e0310549 |pmid=39312548 |pmc=11419359 }}</ref>
*''[[Volvox barberi]]''
*''[[Volvox capensis]]''
*''[[Volvox ferrisii]]''
*''[[Volvox globator]]''
*''[[Volvox kirkiorum]]''
*''[[Volvox longispiniferus]]''<ref>{{cite journal|doi= 10.1371/journal.pone.0235622|doi-access= free|title= A new preferentially outcrossing monoicous species of ''Volvox'' sect. ''Volvox'' (Chlorophyta) from Thailand|date= 2020|last1= Nozaki|first1= Hisayoshi|last2= Mahakham|first2= Wuttipong|last3= Heman|first3= Wirawan|last4= Matsuzaki|first4= Ryo|last5= Kawachi|first5= Masanobu|journal= PLOS ONE|volume= 15|issue= 7|pages= e0235622|pmid= 32614898|pmc= 7332039|bibcode= 2020PLoSO..1535622N}}</ref>
*''[[Volvox merrillii]]''
*''[[Volvox perglobator]]''
*''[[Volvox prolificus]]''
*''[[Volvox rousseletii]]''
'''Unplaced to section'''
*''[[Volvox fertilis]]''<ref>{{cite journal|title=On some freshwater algae from Egypt|last1=Nayal|first=A.A.|journal=Revue algologique|date=1934|volume=8|issue=3–4|pages=311–319|url=https://www.biodiversitylibrary.org/item/281372#page/30/mode/1up}}</ref>
{{div col end}}

Although the genus ''Volvox'' is easy to identify, species-level identification of ''Volvox'' can be difficult.<ref name=Smith1944/> Species are morphologically distinguished based on a variety of characters including zygote morphology, developmental characteristics, and sexual characteristics (e.g. [[dioicy]] or [[monoicy]]).<ref name=Nozaki2015/><ref name=Nozaki2024/>

== Evolution ==
''Volvox'' is [[polyphyletic]]. The section containing the type species, ''Volvox'' sect. ''Volvox'', is [[sister group|sister]] to the rest of the family. Other members of ''Volvox'' are dispersed within three clades, all nested within ''Eudorina''.<ref name=Lindsey2024>{{Cite journal |last1=Lindsey |first1=Charles Ross |last2=Knoll |first2=Andrew H. |last3=Herron |first3=Matthew D. |last4=Rosenzweig |first4=Frank |date=2024-04-10 |title=Fossil-calibrated molecular clock data enable reconstruction of steps leading to differentiated multicellularity and anisogamy in the Volvocine algae |journal=BMC Biology |volume=22 |issue=1 |pages=79 |doi=10.1186/s12915-024-01878-1 |issn=1741-7007 |pmid=38600528 |doi-access=free|pmc=11007952 |bibcode=2024BMCB...22...79L }}</ref>

Ancestors of ''Volvox'' transitioned from single cells that initially resembled ''[[Chlamydomonas]]'' to form multicellular colonies at least {{Ma|200}}, during the [[Triassic]] [[Geologic time scale|period]].<ref name="daily" /><ref name="Herron2009">{{cite journal |last1=Herron |first1=MD |last2=Hackett |first2=JD |last3=Aylward |first3=FO |last4=Michod |first4=RE |date=2009 |title=Triassic origin and early radiation of multicellular volvocine algae |journal=Proceedings of the National Academy of Sciences, USA |doi=10.1073/pnas.0811205106 |pmid=19223580 |volume=106 |issue=9 |pages=3254–3258 |bibcode=2009PNAS..106.3254H |pmc=2651347|doi-access=free }}</ref>
Genera intermediate in morphology, such as ''Gonium'', contain 16 ''Chlamydomonas''-like cells and are thought to represent intermediate stages in evolution. An estimate using [[DNA sequence]]s from about 45 different species of volvocine green algae, including ''Volvox'', suggests that the transition from single cells to undifferentiated multicellular colonies took about 35 million years.<ref name="daily" /><ref name="Herron2009" />

== References ==
{{Reflist}}

== Notes ==
{{reflist|group=note}}

== External links ==
{{Commons category}}
{{Wikispecies|Volvox}}
* [http://protist.i.hosei.ac.jp/pdb/Images/Chlorophyta/Volvox/index.html ''Volvox'' description with pictures] from a [[Hosei University]] website
* [[YouTube]] videos of ''Volvox'':
** [https://www.youtube.com/watch?v=2HtArsoZQzU Volvox micro-motility in Lake Oroville, CA]
** [https://www.youtube.com/watch?v=fqEHbJbuMYA Life cycle and inversion]
** [https://www.youtube.com/watch?v=V6Yg2BQy82w Waltzing ''Volvox'']
** [https://www.youtube.com/watch?v=w8O4OolGcPg Spinning ''Volvox'']
* [http://www.microscopy-uk.org.uk/mag/artdec03/volvox.html ''Volvox'', one of the 7 Wonders of the Micro World] by Wim van Egmond, from Microscopy-UK
* [https://web.archive.org/web/20141228154317/http://www.metamicrobe.com/volvox/ ''Volvox carteri''] at MetaMicrobe.com, with modes of reproduction, brief facts

{{Antonie van Leeuwenhoek}}
{{Taxonbar|from=Q310495}}
{{Authority control}}

[[Category:1700 in science]]
[[Category:Chlamydomonadales]]
[[Category:Chlamydomonadales genera]]