Yellow-green algae or the Xanthophyceae (xanthophytes) are an important group of
heterokont
Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which a ...
algae. Most live in fresh water, but some are found in marine and soil habitats. They vary from single-celled
flagellates to simple colonial and filamentous forms. Xanthophyte
chloroplasts contain the
photosynthetic pigments
chlorophyll ''a'',
chlorophyll ''c'',
β-carotene
β-Carotene is an organic, strongly coloured red-orange pigment abundant in fungi, plants, and fruits. It is a member of the carotenes, which are terpenoids (isoprenoids), synthesized biochemically from eight isoprene units and thus having 40 ...
, and the
carotenoid diadinoxanthin.
Unlike other heterokonts, their chloroplasts do not contain
fucoxanthin
Fucoxanthin is a xanthophyll, with formula C42H58O6. It is found as an accessory pigment in the chloroplasts of brown algae and most other heterokonts, giving them a brown or olive-green color. Fucoxanthin absorbs light primarily in the blue-green ...
, which accounts for their lighter colour. Their storage
polysaccharide is
chrysolaminarin.
Xanthophyte cell walls are produced of
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...
and
hemicellulose
A hemicellulose (also known as polyose) is one of a number of heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose in almost all terrestrial plant cell walls.Scheller HV, Ulvskov Hemicelluloses.// Annu Rev ...
.
They appear to be the closest relatives of the
brown algae
Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and p ...
.
Classifications
The species now placed in the Xanthophyceae were formerly included in the
Chlorophyceae. In 1899, Lüther created the group Heterokontae for green algae with unequal flagella. Pascher (1914) included the Heterokontae in the
Chrysophyta. In 1930, Allorge renamed the group as Xanthophyceae.
The monadoid (unicellular flagellates) and also sometimes the amoeboid species have been included by some authors in the
Protozoa or
Protista
A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...
, as order Heterochloridina (e.g., Doflein and Reichenow, 1927-1929), as class Xanthomonadina, with orders Heterochloridea and Rhizochloridea (e.g., Deflandre, 1956), as order Heterochlorida (e.g., Hall, 1953, Honigberg et al., 1964), as order Heteromonadida (e.g., Leedale, 1983), or as subclass Heterochloridia (e.g., Puytorac et al., 1987). These groups are called
ambiregnal protist
Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms. To an end-user who only deals with names of species, with some awareness that species ...
s, as names for these have been published under either or both of the ICZN and the ICN.
AlgaeBase (2020)
Xanthophyceae have been divided into the following five orders in some classification systems:
* ''
Dictyosphaeriopsis''
* ''
Groenlandiella''
* ''
Halosphaeropsis''
* ''
Pelagocystis''
* ''
Polyedrium''
* ''
Pseudopleurochloris''
* ''
Raphidosphaera''
* ''
Sphaerochloris''
* ''
Tiresias
In Greek mythology, Tiresias (; grc, Τειρεσίας, Teiresías) was a blind prophet of Apollo in Thebes, famous for clairvoyance and for being transformed into a woman for seven years. He was the son of the shepherd Everes and the nym ...
''
* Order
Botrydiales Schaffner 1922
** Family
Botrydiaceae Rabenhorst 1863
*** ''
Asterosiphon''
*** ''
Botrydium''
*** ''
Polychloris''
* Order
Mischococcales Fritsch 1927
** Family
Botrydiopsidaceae Hibberd 1980
*** ''
Botrydiopsis''
*** ''
Excentrochloris''
*** ''
Perone''
** Family
Botryochloridaceae Pascher 1938
*** ''
Botryochloris''
*** ''
Chlorellidiopsis''
*** ''
Chlorellidium''
*** ''
Ducellieria''
*** ''
Heterodesmus''
*** ''
Ilsteria''
*** ''
Raphidiella''
*** ''
Sphaerosorus''
*** ''
Tetraktis''
** Family
Centritractaceae Pascher 1937
*** ''
Bumilleriopsis''
*** ''
Centritractus''
*** ''
Pseudotetraëdron''
** Family
Characiopsidaceae Pascher 1938
*** ''
Characiopsis''
*** ''
Chlorokoryne''
*** ''
Chlorothecium''
*** ''
Chytridiochloris''
*** ''
Dioxys''
*** ''
Harpochytrium''
*** ''
Hemisphaerella''
*** ''
Lutherella''
*** ''
Peroniella''
** Family
Chloropediaceae Pascher 1931
*** ''
Chloropedia''
** Family
Gloeobotrydaceae Pascher 1937
*** ''
Chlorosaccus''
*** ''
Asterogloea''
*** ''
Dictyosphaeriopsis''
*** ''
Gaumiella''
*** ''
Gloeobotrys''
*** ''
Gloeoskene''
*** ''
Gloeosphaeridium''
*** ''
Merismogloea''
** Family
Gloeopodiaceae Pascher 1938
*** ''
Gloeopodium''
** Family
Mischococcaceae Pascher 1912
*** ''
Mischococcus''
** Family
Ophiocytiaceae Lemmermann 1899
*** ''
Ophiocytium''
** Family
Pleurochloridaceae Pascher 1937
*** ''
Acanthochloris''
*** ''
Actinellipsoidion''
*** ''
Arachnochloris''
*** ''
Aulakochloris''
*** ''
Bracchiogonium''
*** ''
Chlorallanthus''
*** ''
Chlorapion''
*** ''
Chlorarkys''
*** ''
Chloridella''
*** ''
Chlorocloster''
*** ''
Chlorogibba''
*** ''
Diachros''
*** ''
Endochloridion''
*** ''
Isthmochloron''
*** ''
Keriosphaera''
*** ''
Leuvenia''
*** ''
Meringosphaera''
*** ''
Monallanthus''
*** ''
Monodus''
*** ''
Nephrodiella''
*** ''
Osterhoutia''
*** ''
Pleurochloridella''
*** ''
Pleurochloris''
*** ''
Pleurogaster''
*** ''
Polyedriella''
*** ''
Polygoniochloris''
*** ''
Prismatella''
*** ''
Pseudogoniochloris''
*** ''
Pseudopolyedriopsis''
*** ''
Rhomboidella ''
*** ''
Schilleriella''
*** ''
Skiadosphaera''
*** ''
Sklerochlamys''
*** ''
Tetraplektron''
*** ''
Trachychloron''
** Family
Trypanochloridaceae Geitler ex Pascher 1938
*** ''
Trypanochloris''
* Order
Rhizochloridales Pascher 1925
*** ''
Garciamyxa''
*** ''
Herreramyxa''
*** ''
Requejomyxa''
** Family
Myxochloridaceae Pascher 1937
*** ''
Myxochloris''
** Family
Rhizochloridaceae Pascher 1925
*** ''
Aldavemyxa''
*** ''
Heterocalycina''
*** ''
Rhizochloris''
** Family
Stipitococcaceae Pascher ex Smith 1933
*** ''
Rhizolekane''
*** ''
Stipitococcus''
*** ''
Stipitoporos''
* Order
Tribonematales Pascher 1939
** Family
Heterodendraceae Pascher 1939
*** ''
Heterodendron''
** Family
Heteropediaceae Hibberd 1982
*** ''
Capitulariella''
*** ''
Chaetopedia''
*** ''
Heterococcus''
*** ''
Heteropedia''
*** ''
Sphagnoikos''
** Family
Neonemataceae Ettl 1977
*** ''
Neonema''
** Family
Tribonemataceae West 1904
*** ''
Brachynematella''
*** ''
Bumilleria''
*** ''
Tribonema''
** Family
Xanthonemataceae Silva 1980
*** ?''
Hormotheca''
*** ''
Heterotrichella''
*** ''
Xanthonema''
* Order
Vaucheriales Nägeli ex Bohlin 1901[Christensen, T. 1987. ''Seaweeds of the British Isles.'' Volume 4 Tribophyceae (Xanthophyceae). British Museum (Natural History), London ]
** Family
Vaucheriaceae (Gray) Dumortier 1822
*** ''
Pseudodichotomosiphon''
*** ''
Vaucheria''
*** ''
Vaucheriella''
Lüther (1899)
Classification according to Lüther (1899):
* Class Heterokontae
** Order Chloromonadales
** Order Confervales
Pascher (1912)
Classification according to Pascher (1912):
* Heterokontae
** Heterochloridales
** Heterocapsales
** Heterococcales
** Heterotrichales
** Heterosiphonales
Fritsch (1935)
Fritsch (1935) recognizes the following orders in the class Xanthophyceae:
*Order Heterochloridales
** Suborder Heterochlorineae
*** Family Heterochloridaceae (e.g., ''
Heterochloris'')
** Suborder Heterocapsineae
*** Family Heterocapsaceae (e.g., ''
Chlorogloea'')
** Suborder Heterodendrineae
*** Family Mischococcaceae (e.g., ''
Mischococcus'')
** Suborder Heterorhizidineae
*** Family Heterorhizidaceae (e.g., ''
Rhizolekane'')
*Order Heterococcales
** Family Halosphaeraceae (e.g., ''
Halosphaera
''Halosphaera'' is a genus of green algae in the order Pyramimonadales
Pyramimonadales are an order of green algae in the Chlorophyta. The chloroplasts of phototrophic euglenids probably came from endosymbiosis with a member of this order.
T ...
'')
** Family Myxochloridaceae (e.g., ''
Myxochloris'')
** Family Chlorobotrydaceae(e.g., ''
Chlorobotrys'')
** Family Chlorotheciaceae (e.g., ''
Chlorothecium'')
** Family Ophiocytiaceae (e.g., ''
Ophiocytium'')
*Order Heterotrichales
** Family Tribonemataceae (e.g., ''
Tribonema'')
** Family Heterocloniaceae (e.g., ''
Heterodendron''
*Order Heterosiphonales
** Family Botrydiaceae (e.g., ''
Botrydium'')
Smith (1938)
In the classification of
Smith (1938), there are six orders in the class Xanthophyceae, placed in the division Chrysophyta:
*Order
Heterochloridales (e.g., ''
Chlorochromonas'')
*Order
Rhizochloridales (e.g., ''
Chlorarachnion'')
*Order
Heterocapsales (e.g., ''
Chlorosaccus'')
*Order
Heterotrichales (e.g., ''
Tribonema'')
*Order
Heterococcales (e.g., ''
Botrydiopsis'')
*Order
Heterosiphonales (e.g., ''
Botrydium'')
Pascher (1939)
Pascher (1939) recognizes 6 classes in Heterokontae:
*Class Heterochloridineae
*Class Rhizochloridineae
*Class Hetcrocapsineae
*Class Heterococcincae
*Class Hetcrotrichineae
*Class Heterosiphonineae
Copeland (1956)
Copeland (1956) treated the group as order Vaucheriacea:
* Kingdom
Protoctista
** Phylum
Phaeophyta
*** Class
Heterokonta
Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which a ...
**** Order Vaucheriacea
***** Family Chlorosaccacea
***** Family Mischococcacea
***** Family Chlorotheciacea
***** Family Botryococcacea
***** Family Stipitococcacea
***** Family Chloramoebacea
***** Family Tribonematacea
***** Family Phyllosiphonacea
Ettl (1978), van den Hoek et al. (1995)
In a classification presented by
van den Hoek, Mann and Jahns (1995), based on the
level of organization An integrative level, or level of organization, is a set of phenomena emerging from pre-existing phenomena of a lower level. The levels concept is an intellectual framework for structuring reality. It arranges all entities, structures, and processe ...
of the
thallus
Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms ...
, there are seven orders:
* Order
Chloramoebales (e.g., ''
Chloromeson'') - flagellate organisms
* Order
Rhizochloridales (e.g., ''
Rhizochloris,
Myxochloris'') - ameboid organisms
* Order
Heterogloeales (e.g., ''
Gloeochloris'') - palmelloid (tetrasporal) organisms
* Order
Mischococcales (e.g., ''
Chloridella,
Botrydiopsis,
Characiopsis,
Ophiocytium'') - coccoid organisms
* Order
Tribonematales (e.g., ''
Tribonema,
Heterococcus,
Heterodendron'') - filamentous organization
* Order
Botrydiales (e.g., ''
Botrydium'') - siphonous organization; sexual reproduction
isogamous or anisogamous
* Order
Vaucheriales (e.g., ''
Vaucheria'') - siphonous organization; sexual reproduction oogamous
These are the same orders of the classification of Ettl (1978), an updated version of the classic work by Pascher (1939).
Ultrastructural
Ultrastructure (or ultra-structure) is the architecture of cells and biomaterials that is visible at higher magnifications than found on a standard optical light microscope. This traditionally meant the resolution and magnification range of a co ...
and
molecular studies shows that the Mischococcales might be paraphyletic, and the Tribonematales and Botrydiales polyphyletic, and suggests two orders at most be used until the relationships within the division are sorted.
Maistro et al. (2009)
Informal groups, according to Maistro et al. (2009):
* Botrydiopsalean clade
* Chlorellidialean clade
* Tribonematalean clade
* Vaucherialean clade
Unicellular flagellates, amoeboid and palmelloid taxa were not included in this study.
Adl et al. (2005, 2012)
According to Adl et al. (2005, 2012):
* Tribonematales (genera ''Botrydium, Bumilleriopsis, Characiopsis, Chloromeson, Heterococcus, Ophiocytium, Sphaerosorus, Tribonema, Xanthonema'')
* Vaucheriales (genus ''Vaucheria'')
File:Stipitococcus capense.svg, ''Stipitococcus capense'' (Rhizochloridales)
File:British fresh-water algae, exclusive of Desmidieae and Diatomaceae (1882-1884) (20231360259).jpg, ''Ophiocytium arbusculum'' (Mischococcales), formerly ''Sciadium arbuscula''
File:Alger, Botydium granulatum, Nordisk familjebok.png, ''Botrydium granulatum'' (Botrydiales)
File:Vaucheria sp thallus 01.jpg, ''Vaucheria'' sp. (Vaucheriales), thallus
File:Vaucheria sp sexial reproductive organ01.jpg, ''Vaucheria'' sp., sexual reproductive organs
File:British fresh-water algae, exclusive of Desmidieae and Diatomaceae (1882-1884) (19795451234).jpg, ''Vaucheria'' sp.
File:Album général des Cryptogames, Pl. 21.jpg, Other genera
See also
*
Coccolithophore
Coccolithophores, or coccolithophorids, are single celled organisms which are part of the phytoplankton, the autotrophic (self-feeding) component of the plankton community. They form a group of about 200 species, and belong either to the king ...
*
Cyanobacteria
*
Diatom
References
{{Taxonbar, from=Q745912