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 ...
algae. Most live in fresh water, but some are found in marine and soil habitats. They vary from single-celled
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 their ...
s to simple colonial and filamentous forms. Xanthophyte
chloroplast
A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...
s contain the
photosynthetic
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...
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
Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpki ...
diadinoxanthin
Diadinoxanthin is a pigment found in phytoplankton. It has the formula C40H54O3. It gives rise to the xanthophylls diatoxanthin and dinoxanthin.
Diadinoxanthin is a plastid pigment. Plastid pigments include chlorophylls a and c, fucoxanthin, hete ...
.
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
Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...
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 wall ...
and
hemicellulose
A hemicellulose (also known as polyose) is one of a number of heteropolymer, heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose in almost all embryophyte, terrestrial plant cell walls.Scheller HV, Ulvskov H ...
.
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 po ...
.
Classifications
The species now placed in the Xanthophyceae were formerly included in the
Chlorophyceae
The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. They are usually green due to the dominance of pigments chlorophyll a and chlorophyll b. The chloroplast may be discoid, p ...
. 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
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
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 excl ...
, 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 nymph ...
''
* 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
''Heterococcus'' is a genus of yellow-green algae
Yellow-green algae or the Xanthophyceae (xanthophytes) are an important group of heterokont algae. Most live in fresh water, but some are found in marine and soil habitats. They vary from singl ...
''
*** ''
Heteropedia''
*** ''
Sphagnoikos''
** Family
Neonemataceae Ettl 1977
*** ''
Neonema''
** Family
Tribonemataceae West 1904
*** ''
Brachynematella''
*** ''
Bumilleria''
*** ''
Tribonema
''Tribonema'' is a genus of filamentous, freshwater yellow-green algae. The holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally ...
''
** 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
''Vaucheria'' is a genus of Xanthophyceae or yellow-green algae known as water felt. It is one of only two genera in the family Vaucheriaceae. The type species of the genus is '' Vaucheria disperma''.
The genus was circumscribed by Augustin Py ...
''
*** ''
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 Heterotrichale