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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 a model species,
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Schematic representation of the phylogenetic relationships of the volvocine algae and the parallel evolution of the spheroidal colony. Volvocine algae range from the unicellular
Chlamydomonas to the multicellular Volvox through various intermediate forms and are used as a model for research into the
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facing outwards. During this process reproductive cells 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
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sperm by one mating type and relatively larger immotile eggs by another. Among the
Volvocaceans are thus the simplest organisms with distinguishable male and female members. In all Volvocaceans, the fertilization reaction results in the production of a dormant
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to Volvox, and the other in the genus
Astrephomene. The phylogeny is based on previous reports. All drawings and photographs represent side views of individuals with anterior ends orienting toward the top of this
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a colony normally has either 128 or 64 cells, of which those in the anterior region have only a somatic function, while those in the posterior region can reproduce; the ratio being 3:5. In
353:, on the other hand, the division of labor is complete with reproductive cells being set aside during cell division, and they never assume somatic functions or develop functional flagella.
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Spheroidal colony inversion evolved twice during evolution of the
Chlamydomonadales. In the Volvocaceae inversion first occurred when the Volvocaceae diverged from the closely related
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Thus, the simplest
Volvocaceans are colonial organisms but others are truly multicellular organisms. Larger volvocaceans have evolved a specialized form of
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evolution of multicellularity. The spheroidal colony is thought to have evolved twice independently within this group: once in the
Volvocaceae, from
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590:
504:"Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta)"
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form hollow spheres, the former consisting of 16 cells, the latter of 32 to 64 cells. In these genera each cell can reproduce a new organism by
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Other genera of
Volvocaceans represent another principle of biological development as each organism develops differented cell types. In
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in 1834, and is known in older classifications as the
Volvocidae. All species are colonial and inhabit freshwater environments.
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Colony inversion during development is a special characteristic of this order that results in new colonies having their
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418:. Inversion differs between the two lineages: rotation of daughter protoplasts during successive cell divisions in
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380:) capable of surviving in harsh environments. Once conditions have improved the zygospore germinates and undergoes
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The simplest of the
Volvocaeans are ordered assemblies of cells, each similar to the related unicellular protist
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284:, for example, each individual organism is a flat plate consisting of 4 to 16 separate cells, each with two
459:[Third contribution to knowledge of greater organization in the direction of the smallest realm].
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the reproductive cells are derived from cells looking and behaving like somatic cells. In
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Yamashita S, Arakaki Y, Kawai-Toyooka H, Noga A, Hirono M, Nozaki H (November 2016).
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only very few cells are able to reproduce new individuals, and in some species of
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554:"Multicellularity: The Evolution of Differentiation §The Volvocaceans"
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Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin
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Material was copied from this source, which is available under a
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Creative Commons Attribution 4.0 International License
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414:(see figure). It also occurred during evolution of
278:and embedded in a gelatinous matrix. In the genus
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878:Taxa named by Christian Gottfried Ehrenberg
560:(6th ed.). Sunderland (MA): Sinauer. (
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333:and only a few are reproductive. In
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587:"Miller Group: Research Description"
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388:offspring of both mating types.
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552:Gilbert, Scott F. (2000).
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260:. The family was named by
469:"VOLVOCINA Nova Familia."
288:. Similarly, the genera
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46:Scientific classification
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471:(Volvocina New Family.)
251:, including the typical
873:Chlorophyceae families
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336:Pleodorina californica
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558:Developmental Biology
463:(in German): 145–336.
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593:Biological Sciences
155:Hemiflagellochloris
455:Ehrenberg (1833).
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868:Chlamydomonadales
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804:Open Tree of Life
617:Taxon identifiers
329:, most cells are
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595:. Retrieved
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24:Volvocaceae
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729:iNaturalist
655:Volvocaceae
649:Wikispecies
625:Volvocaceae
574:. NBK10031.
384:to produce
268:Description
245:unicellular
237:Volvocaceae
183:Platydorina
106:Volvocaceae
76:Chlorophyta
862:Categories
546:References
514:(1): 243.
358:heterogamy
350:V. carteri
320:Pleodorina
312:Volvox sp.
197:Stephanoon
190:Pleodorina
72:Division:
822:100371211
664:AlgaeBase
597:August 9,
434:Pandorina
412:Goniaceae
378:zygospore
297:Pandorina
262:Ehrenberg
218:Volvulina
176:Pandorina
162:Lundiella
111:Ehrenberg
817:Tropicos
634:Wikidata
530:27829356
398:flagella
291:Eudorina
286:flagella
141:Eudorina
102:Family:
640:Q654492
521:5103382
437:figure.
386:haploid
382:meiosis
371:diploid
360:called
331:somatic
302:mitosis
148:Hamakko
118:Genera
92:Order:
82:Class:
845:143798
832:432570
829:uBio:
809:391142
793:NZOR:
747:108066
734:121589
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374:zygote
366:motile
362:oogamy
345:Volvox
341:Volvox
326:Volvox
281:Gonium
257:Volvox
241:family
239:are a
211:Volvox
204:Tabris
840:WoRMS
742:IRMNG
708:1VLXF
442:Notes
253:genus
60:Clade
786:3065
781:NCBI
760:5572
755:ITIS
721:8821
716:GBIF
703:EPPO
695:3989
669:4948
599:2016
591:UMBC
566:ISBN
562:NCBI
526:PMID
323:and
294:and
235:The
768:NBN
690:EoL
682:HV6
677:CoL
564:).
516:PMC
243:of
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
