''Chlamydomonas'' ( ) is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

consisting of about 150

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and the ...

s, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as " snow algae". ''Chlamydomonas'' is used as a

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

for

molecular biology Molecular biology is a branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, biomolecular synthesis, modification, mechanisms, and interactio ...

, especially studies of flagellar motility and

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

dynamics, biogenesis, and genetics. One of the many striking features of ''Chlamydomonas'' is that it contains

ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by Gating (electrophysiol ...

s ( channelrhodopsins) that are directly activated by light. Some regulatory systems of ''Chlamydomonas'' are more complex than their

homolog In biology, homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry, ''regardless'' of current functional differences. Evolutionary biology explains homologous structures as retained her ...

s in

Gymnosperms The gymnosperms ( ; ) are a group of woody, perennial Seed plant, seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include Pinophyta, conifers, cycads, Ginkgo, and gnetoph ...

, with evolutionarily related regulatory proteins being larger and containing additional domains.

Molecular phylogeny Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies indicated that the traditional genus ''Chlamydomonas'' as defined using morphological data, was

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

within Volvocales. Many species were subsequently reclassified (e.g., '' Oogamochlamys, Lobochlamys''), and many other "''Chlamydomonas''" s.l. lineages are still to be reclassified.

Etymology

The name ''Chlamydomonas'' comes from the Greek roots ''chlamys'', meaning cloak or mantle, and ''monas'', meaning solitary, now used conventionally for unicellular flagellates.

Description

Morphology

All ''Chlamydomonas'' are motile, unicellular organisms. Cells are generally spherical to cylindrical in shape, but may be elongately spindle-shaped, and a papilla may be present or absent. Chloroplasts are green and usually cup-shaped. A key feature of the genus is its two anterior flagella, each as long as the other. The flagellar

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nanometer, nm and have an inner diameter bet ...

s may each be disassembled by the cell to provide spare material to rebuild the other's microtubules if they are damaged. * Cell wall is made up of a glycoprotein and non-cellulosic polysaccharides instead of cellulose. * Two anteriorly inserted whiplash flagella. Each flagellum originates from a basal granule in the anterior papillate or non-papillate region of the cytoplasm. Each flagellum shows a typical 9+2 arrangement of the component fibrils. * Contractile vacuoles are near the bases of flagella. * Prominent cup or bowl-shaped chloroplast is present. The chloroplast contains bands composed of a variable number of the photosynthetic thylakoids which are not organised into grana-like structures. * The nucleus is enclosed in a cup-shaped chloroplast, which has a single large

pyrenoid Pyrenoids are sub-cellular phase-separated micro-compartments found in chloroplasts of many algae,Giordano, M., Beardall, J., & Raven, J. A. (2005). CO2 concentrating mechanisms in algae: mechanisms, environmental modulation, and evolution. ''An ...

where starch is formed from photosynthetic products. Pyrenoid with starch sheath is present in the posterior end of the chloroplast. * Eye spot present in the anterior portion of the chloroplast. It consists of two or three, more or less parallel rows of linearly arranged fat droplets.

Species

About 500 species of ''Chlamydomonas'' have been described. *''Chlamydomonas acidophila'' * ''Chlamydomonas caudata'' * ''Chlamydomonas ehrenbergii'' * '' Chlamydomonas elegans'' * '' Chlamydomonas moewusii'' * ''Chlamydomonas muriella'' * '' Chlamydomonas nivalis'' * ''Chlamydomonas ovoidae'' * ''Chlamydomonas priscuii'' * ''Chlamydomonas smithii'' * '' Chlamydomonas reinhardtii''

Ecology

''Chlamydomonas'' is widely distributed in freshwater or damp soil. It is generally found in a habitat rich in ammonium salt. It possesses red eye spots for photosensitivity and reproduces both asexually and sexually. ''Chlamydomonass asexual reproduction occurs by

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are ...

s, aplanospores, hypnospores, or a palmella stage, while its sexual reproduction is through

isogamy Isogamy is a form of sexual reproduction that involves Gamete, gametes of the same Morphology (biology), morphology (indistinguishable in shape and size), and is found in most Unicellular organism, unicellular eukaryotes. Because both gametes lo ...

anisogamy Different forms of anisogamy: A) anisogamy of motile cells, B) 283x283px Anisogamy is a form of sexual reproduction">egg cell">oogamy (egg cell and sperm cell), C) anisogamy of non-motile cells (egg cell and spermatia).">283x283px Anisogamy is ...

oogamy Oogamy is a form of anisogamy where the gametes differ in both size and form. In oogamy the large female gamete (also known as ovum) is immotile, while the small male gamete (also known as spermatozoon) is mobile. Oogamy is a common form of an ...

Nutrition

Most species are obligate

phototroph Phototrophs () are organisms that carry out photon capture to produce complex organic compounds (e.g. carbohydrates) and acquire energy. They use the energy from light to carry out various cellular metabolic processes. It is a list of common m ...

s but '' C. reinhardtii'' and ''C. dysostosis'' are facultative heterotrophs that can grow in the dark in the presence of acetate as a carbon source.

Uses

Some ''Chlamydomonas'' are edible.

References

External links

''Chlamydomonas'' Center

''Chlamydomonas reinhardtii'' Transcription Factor Database

3D electron microscopy structures of Chlamydomonas-related proteins at the EM Data Bank(EMDB)

The Seaweed Site

Ancient gene family protects algae from salt and cold in an Antarctic lake
on: EurekAlert!, 20-Aug-2020, on species UWO241 and in Lake Bonney (Antarctica) {{Authority control Chlamydomonadales genera Chlamydomonadaceae Taxa named by Christian Gottfried Ehrenberg