''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 Snow algae are a group of freshwater micro-algae that grow in the alpine and polar regions of the Earth. Snow algae have been found on every continent but are restricted to areas with temperatures between 0°C-10°C. Snow algae are pigmented by ...

". ''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 Channelrhodopsins are a subfamily of retinylidene proteins (rhodopsins) that function as light-gated ion channels. They serve as sensory photoreceptors in unicellular green algae, controlling phototaxis: movement in response to light. Expressed ...

) 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 Regulation is the management of complex systems according to a set of rules and trends. In systems theory, these types of rules exist in various fields of biology and society, but the term has slightly different meanings according to context. Fo ...

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 Chlamydomonadales, also known as Volvocales, are an order of flagellated or pseudociliated green algae, specifically of the Chlorophyceae.See the NCBIbr>webpage on Chlamydomonadales Data extracted from the Chlamydomonadales can form planar or ...

. Many species were subsequently reclassified (e.g., ''

Oogamochlamys ''Oogamochlamys'' is a genus of green algae in the family Chlamydomonadaceae.See the NCBI The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Hea ...

Lobochlamys ''Lobochlamys'' is a genus of green algae in the family Chlamydomonadaceae.See the NCBI The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Healt ...

''), 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 This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary ...

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 moewusii'' is a species of unicellular green alga belonging to the genus ''Chlamydomonas''. ''C. moewusii'' is typically a freshwater species and occupies a significant position as a model organism for various scientific studies ...

'' * ''Chlamydomonas muriella'' * '' Chlamydomonas nivalis'' * ''Chlamydomonas ovoidae'' * ''Chlamydomonas priscuii'' * ''Chlamydomonas smithii'' * ''

Chlamydomonas reinhardtii ''Chlamydomonas reinhardtii'' is a single-cell green alga about 10 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and a ...

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 ...

aplanospore {{Short pages monitor