Chlamydomonas Ehrenberg, 1833, nom. cons.

Holotype species: Chlamydomonas reinhardtii P.A.Dangeard

Original publication: Ehrenberg, C.G. (1834). Dritter Beitrag zur Erkenntniss grosser Organisation in der Richtung des kleinsten Raumes. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1833: 145-336, pls I-XIII.

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Type designated in: Pröschold, T. & Silva, P.C. (2007). Proposal to change the listed type of Chlamydomonas Ehrenb., nom. cons.. Taxon 56: 595-596.

Description: Unicellular thalli typically spherical to subspherical, but may be fusiform. Each cell typically with two anterior contractile vacuoles, but these may be absent or numerous (depending upon species), with two isokont, anterior flagella. Chloroplast single per cell and extremely variable, variants species specific and provide basis for defining species group or "Hauptgruppen" (sensu Ettl). Chloroplasts variously cup-shaped (Euchlamydomonas, Chlamydella, Bicocca, Pleiochloris), band-shaped (Chlorogoniella), bipolar (Amphichloris), "H"-shaped (Agloë, Pseudagloë) to indistinct (Sphaerella), or even highly dissected (e.g., C. zebra). Pyrenoids one to several with position variable depending upon the species basal (Euchlamydomonas), lateral (Chlamydella, Bicocca, Chlorogoniella), or axial (Agloë, Pseudagloë). Eyespot prominent in most species, at cell anterior embedded in chloroplast. Nucleus single and typically central; < 5 µm. Flagellar root system cruciate and composed of four sets of microtubule systems (4-2-4-2 pattern). Basal bodies, connected by striated (proximal and distal) fiber systems, exhibit clockwise absolute configuration. Mitosis characterized as closed spindle type, spindle collapses at telophase. Phycoplast system of microtubules develops in the plane of cytokinesis. First division typically longitudinal, although rotation of cell contents may obscure this; some species exhibit "true" transverse division. Asexual reproduction by zoosporogenesis. Daughter cells produce enzymes that lyse the parental sporangial wall to effect release. Sporangial wall autolysins vary between species and 15 different autolysin types described (sensu Schlösser); these used as basis for intrageneric classification. Thus, C. globosa, C. smithii, C. incerta and C. reinhardtii in autolysin group 1; whereas C. indica, C. eugametos, C. moewusii, and C. starrii in autolysin group 2. Four different forms of sporangial dissolution present 1) partial dissolution with explosive inversion, 2) total dissolution, 3) partial dissolution with pore formation, and 4) fragmentation of sporangium. Motility variable (from "zoospores only motile stage" to "all stages motile") and species specific. Akinetes may form by thickening of vegetative cell wall. Palmella stages common. Sexual reproduction isogamous, anisogamous, or oogamous; homothallic or heterothallic, depending on the species. Gametes naked or walled with wall discarded during fusion. Gametogenesis triggered by sub-optimal environmental conditions (loss of nitrogen). In C. reinhardtii, mixture of opposite mating types leads to immediate adhesion of flagella from two cells of each mating type. Glycoproteins (agglutinins [preferred term] or gamones) excreted by gametes into the media induce union. Agglutination reaction is specific to gametes; active molecule present on flagella of gametogenic cells only. Mating structures are activated and a fertilization tube, derived from the mt+ cell, connects the two cells. Fusing cells are quadriflagellate and may remain motile for several hours. Zygote wall ornamented or unornamented. Zygote germinates to form 2-8 meiospores. Chromosome number variable (N = 8-38) depending upon the species and investigator. Diagnosis emended by Pröshold et al. (2001: 285).

Information contributed by: M. Buchheim. The most recent alteration to this page was made on 2018-01-01 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Gender: This genus name is currently treated as feminine.

Most recent taxonomic treatment adopted: Pentecost, A. (2002). Order Volvocales. In: The Freshwater Algal Flora of the British Isles. An identification guide to freshwater and terrestrial algae. (John, D.M., Whitton, B.A. & Brook, A.J. Eds), pp. 303-327. Cambridge: Cambridge University Press.

Comments: Species of the genus are widespread in freshwater but marine species are less common. Habitats include soil, temporary pools, eutrophic lakes and melting snow (e.g., C. nivalis). Two marine species (C. provasolii and C. hedleyi) are found only in symbiotic association with foraminifera. Cell wall composed of seven distinct layers with hydroxyproline-rich glycoproteins as major constituents. No evidence for cellulose has been determined. Lattice structure of the cell walls reveals considerable diversity. Chlamydomonas reinhardtii and the multicellular Volvox aureus, Pandorina morum, and Eudorina elegans have Type I lattice structure. In contrast, C. moewusii (and many other species) with Type II lattice structure. Type II structure also observed in Haematococcus, Polytoma, Carteria, Chloromonas, and Chlorogonium. Chlamydomonas asymmetrica with Type III lattice. Chlamydomonas is a large heterogeneous assemblage of taxa with morphological and biochemical data suggesting distinct lineages. Molecular evidence demonstrated considerable differences between the physical maps of the chloroplast genomes from C. reinhardtii and C. moewusii. Nuclear genes also indicate that the genus is diverse, but, in addition, nuclear-encoded rRNA data suggest that Chlamydomonas is not monophyletic. Species in Euchlamydomonas most closely allied with colonial flagellates such as Volvox and Eudorina. Chlamydomonas mexicana (= C. oblonga sensu Ettl) and C. peterfii (= C. asymmetrica in revised SAG catalog) closely allied, corroborating biochemical evidence. Chlamydomonas eugametos (= C. moewusii in revised SAG catalog), C. moewusii, C. indica (= C. moewusii in revised SAG catalog), C. pitschmannii and C. geitleri (= C. noctigama in revised SAG catalog) form coherent lineage based on rRNA sequence data. Sequence data suggest that C. humicola (= C. applanata in revised SAG catalog) is closely allied with Haematococcus and the colonial Stephanosphaera. Ettl and Schlösser are currently re-examining the genus Chlamydmonas. Taxonomic revision is inevitable and on-going and will dramatically alter the genus.

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Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=43319

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 01 January 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 04 December 2022

 
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