The raphidophytes, formally known as Raphidomonadea or Raphidophyceae (formerly referred to as Chloromonadophyceae and Chloromonadineae), are a small group of

eukaryotic Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

e that includes both marine and freshwater

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

. All raphidophytes are

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 ...

, with large cells (50 to 100 μm), but no cell walls. Raphidophytes possess a pair of flagella, organised such that both originate from the same

invagination Invagination is the process of a surface folding in on itself to form a cavity, pouch or tube. In developmental biology, invagination is a mechanism that takes place during gastrulation. This mechanism or cell movement happens mostly in the vegeta ...

(or gullet). One flagellum points forwards, and is covered in hair-like

mastigonemes Mastigonemes are lateral "hairs" that attach to protistan flagella. Flimsy hairs attach to the flagella of euglenid flagellates, while stiff hairs occur in stramenopile and cryptophyte protists.Hoek, C. van den, Mann, D. G. and Jahns, H. M. ( ...

, while the other points backwards across the cell surface, lying within a

ventral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

groove. Raphidophytes contain numerous ellipsoid chloroplasts, which contain chlorophylls a, c₁ and c₂. They also make use of

accessory pigment Accessory pigments are light-absorbing compounds, found in photosynthetic organisms, that work in conjunction with chlorophyll ''a''. They include other forms of this pigment, such as chlorophyll ''b'' in green algal and higher plant antennae, w ...

s including

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 diadinoxanthin. Unlike other heterokontophytes, raphidophytes do not possess the photoreceptive organelle (or eyespot) typical of this group. In terms of

ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...

, raphidophytes occur as photosynthetic

autotroph An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Wo ...

s across a range of aquatic systems. Freshwater species are more common in acidic waters, such as pools in bogs. Marine species often produce large blooms in summer, particularly in coastal waters. Off the Japanese coast, the resulting

red tide A harmful algal bloom (HAB) (or excessive algae growth) is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, mechanical damage to other organisms, or by other means. HABs are sometimes ...

s often cause disruption to

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, although raphidophytes are not usually responsible for

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

blooms. The position of this group varied in former classifications. Some

protozoologist Protozoology is the study of protozoa, the "animal-like" (i.e., motile and heterotrophic) protists. The Protozoa are considered to be a subkingdom of Protista. They are free-living organisms that are found in almost every habitat. All humans have pr ...

s treated the chloromonads as an order within the phytoflagellates. Some phycologists classified them with the

Xanthophyceae 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 filamen ...

and the

Eustigmatophyceae Eustigmatophytes are a small group (17 genera; ~107 species) of eukaryotic forms of algae that includes marine, freshwater and soil-living species. All eustigmatophytes are unicellular, with coccoid cells and polysaccharide cell walls. Eust ...

in the division

Xanthophyta 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 filament ...

. Others considered them as related to the Chrysophyceae, Dinophyceae, or Cryptophyceae Recently, the heliozoan Actinophyrida was moved to the group.

Taxonomy

Classification based on Cavalier-Smith and Scoble 2013 * Class Raphidomonadea Silva 1980 emend. Cavalier-Smith 2013 aphidophyceae Chadefaud 1950 emend. Silva 1980 s.l.** nplaced genera*** Genus '' Psammamonas'' Grant et al. 2013 *** Genus '' Chloromorum'' Tomas et al. ** Subclass Raphopoda Cavalier-Smith 2013 *** Order Commatiida Cavalier-Smith 1997 **** Family Commatiidae Cavalier-Smith 2013 ***** Genus '' Commation'' Thomsen & Larsen 1993 *** Order Actinophyrida Hartmann 1913 ctinophrydia Kühn 1926; Actinophrydea Hartmann 1913**** Family Actinosphaeriidae Cavalier-Smith 2013 ***** Genus '' Actinosphaerium'' Ritter von Stein 1857 'Camptonema''_Schaudinn_1894;_''Echinosphaerium.html" ;"title="Camptonema.html" ;"title="'Camptonema">'Camptonema'' Schaudinn 1894; ''Echinosphaerium">Camptonema.html" ;"title="'Camptonema">'Camptonema'' Schaudinn 1894; ''Echinosphaerium'' Hovasse 1965] **** Family Helioraphidae Cavalier-Smith 2013 ***** Genus ''Heliorapha'' Cavalier-Smith 2013 **** Family Actinophryidae Dujardin 1841 ***** Genus '' Actinophrys'' Ehrenberg 1830 'Trichoda''_Müller_1773_nomen_oblitum;_''Peritricha_(genus).html" ;"title="Trichoda.html" ;"title="'Trichoda">'Trichoda'' Müller 1773 nomen oblitum; ''Peritricha (genus)">Peritricha'' Bory de St.Vincent 1824 nomen dubium non Stein 1859] ** Subclass Raphidophycidae Cavalier-Smith 2013 [Raphidophyceae Chadefaud 1950 emend. Silva 1980 s.s.; Chloromonadophyceae Rothmaler 1951; Raphidophyta] *** Order Raphidomonadales hattonellales Throndsen 1993; Chloromonadida; Chloromonadales; Raphidomonadida Heywood & Leedale 1983; Chloromonadina Klebs 1892**** Genus '' Viridilobus'' Demir-Hilton et al. 2012 **** Family Fibrocapsaceae Cavalier-Smith 2013 ***** Genus '' Fibrocapsa'' Toriumi & Takano 1973 **** Family Haramonadaceae Cavalier-Smith 2013 ***** Genus '' Haramonas'' Horiguchi 1996 **** Family Chattonellaceae Throndsen ***** Genus '' Oltmannsia'' Schiller 1925 ***** Genus '' Chlorinimonas'' Yamaguchi et al. 2010 ***** Genus '' Heterosigma'' Hada 1967 ex Hara & Chihara 1987 ***** Genus ''

Chattonella ''Chattonella'' is a genus of marine raphidophytes associated with red tides. A technique using monoclonal antibodies can be used to identify the genus, while the RAPD reaction can be used to distinguish between different species within the g ...

'' Biecheler 1936 'Hornellia''_Subrahmanyan_1954;_''Hemieutreptia.html" ;"title="Hornellia.html" ;"title="'Hornellia">'Hornellia'' Subrahmanyan 1954; ''Hemieutreptia">Hornellia.html" ;"title="'Hornellia">'Hornellia'' Subrahmanyan 1954; ''Hemieutreptia'' Hada 1974] **** Family Vacuolariaceae ***** Genus ''Swirenkoiamonas'' Skvortzov 1968 ***** Genus ''Vacuolaria'' Cienkowski 1870 ***** Genus ''Merotricha'' Mereschkowsky 1877 ***** Genus '' Gonyostomum'' Diesing 1866

References

{{Taxonbar, from=Q134928 Ochrophyta