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 single-celled flagellates to simple colonial and filamentous forms. Xanthophyte chloroplasts contain the photosynthetic pigments chlorophyll a, chlorophyll c, β-carotene, and the carotenoid diadinoxanthin. Unlike other Stramenopiles (heterokonts), their chloroplasts do not contain fucoxanthin, which accounts for their lighter colour. Their storage polysaccharide is chrysolaminarin. Xanthophyte cell walls are produced of cellulose and hemicellulose. They appear to be the closest relatives of the brown algae.
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, 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 protists, 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
Order Botrydiales Schaffner 1922
Family Botrydiaceae Rabenhorst 1863 e.g. Botrydium
Order Mischococcales Fritsch 1927
Family Botrydiopsidaceae Hibberd 1980 e.g. Botrydiopsis
Family Botryochloridaceae Pascher 1938 e.g. Ilsteria
Family Centritractaceae Pascher 1937 e.g. Centritractus
Family Characiopsidaceae Pascher 1938 e.g. Characiopsis, Chlorothecium
Family Chloropediaceae Pascher 1931 e.g. Chloropedia
Family Gloeobotrydaceae Pascher 1937 e.g. Gloeobotrys
Family Gloeopodiaceae Pascher 1938 e.g. Gloeopodium
Family Mischococcaceae Pascher 1912 e.g. Mischococcus
Family Ophiocytiaceae Lemmermann 1899 e.g. Ophiocytium
Family Pleurochloridaceae Pascher 1937 e.g. Meringosphaera, Pleurochloris
Family Trypanochloridaceae Geitler ex Pascher 1938 e.g. Trypanochloris
Order Rhizochloridales Pascher 1925
Family Myxochloridaceae Pascher 1937 e.g. Myxochloris
Family Rhizochloridaceae Pascher 1925 e.g. Rhizochloris
Family Stipitococcaceae Pascher ex Smith 1933 e.g. Stipitococcus
Order Tribonematales Pascher 1939
Family Heterodendraceae Pascher 1939 e.g. Heterodendron
Family Heteropediaceae Hibberd 1982 e.g. Heterococcus, Heteropedia
Family Neonemataceae Ettl 1977 e.g. Neonema
Family Tribonemataceae West 1904 e.g. Tribonema
Family Xanthonemataceae Silva 1980 e.g. Xanthonema
Order Vaucheriales Nägeli ex Bohlin 1901
Family Vaucheriaceae (Gray) Dumortier 1822 e.g. Vaucheria
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
Family Heterochloridaceae (e.g., Heterochloris)
Family Heterocapsaceae (e.g., Chlorogloea)
Family Mischococcaceae (e.g., Mischococcus)
Family Heterorhizidaceae (e.g., Rhizolekane)
Order Heterococcales
Family Halosphaeraceae (e.g., Halosphaera)
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
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 of the thallus, 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 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)
See also
Coccolithophore
Cyanobacteria
Diatom
References