The haptophytes, classified either as the Haptophyta, Haptophytina or Prymnesiophyta (named for '' Prymnesium''), are a clade of

algae Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from ...

. The names Haptophyceae or Prymnesiophyceae are sometimes used instead. This ending implies classification at the class rank rather than as a division. Although the

phylogenetics In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

of this group has become much better understood in recent years, there remains some dispute over which rank is most appropriate.

Characteristics

The

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 ...

s are pigmented similarly to those of the

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 ...

s, but the structure of the rest of the cell is different, so it may be that they are a separate line whose chloroplasts are derived from similar

red algal Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...

endosymbionts. The cells typically have two slightly unequal

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

, both of which are smooth, and a unique organelle called a '' haptonema'', which is superficially similar to a flagellum but differs in the arrangement of microtubules and in its use. The name comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''hapsis'', touch, and ''nema'', round thread. The mitochondria have tubular cristae.

Significance

The best-known haptophytes are coccolithophores, which make up 673 of the 762 described haptophyte species, and have an exoskeleton of calcareous plates called coccoliths. Coccolithophores are some of the most abundant marine

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. P ...

, especially in the open ocean, and are extremely abundant as microfossils, forming

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Cha ...

deposits. Other planktonic haptophytes of note include '' Chrysochromulina'' and '' Prymnesium'', which periodically form toxic marine

algal bloom An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term ''algae'' encompas ...

s, and '' Phaeocystis'', blooms of which can produce unpleasant foam which often accumulates on beaches. Haptophytes are economically important, as species such as ''

Pavlova lutheri __NOTOC__ Pavlova may refer to: Persons *Pavlova, the feminine form of Pavlov, a common Russian and Bulgarian family name *Anna Pavlova (1881–1931), Russian ballerina *Anna Pavlova (born 1987), Russian artistic gymnast *Karolina Pavlova, Russian ...

'' and ''

Isochrysis ''Isochrysis'' is a genus of haptophytes. It includes the 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 ...

sp.'' are widely used in the

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lotus ...

industry to feed

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not a ...

and

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

larvae. They contain a large amount of

polyunsaturated fatty acid Polyunsaturated fatty acids (PUFAs) are fatty acids that contain more than one double bond in their backbone. This class includes many important compounds, such as essential fatty acids and those that give drying oils their characteristic proper ...

s such as

docosahexaenoic acid Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, and retina. In physiological literature, it is given the name 22:6(n-3). It can be synthesized from alpha-li ...

(DHA),

stearidonic acid Stearidonic acid (SDA: C18 H28 O2; 18: 4, n-3) is an ω-3 fatty acid, sometimes called moroctic acid. It is biosynthesized from alpha-linolenic acid (ALA: C18H30O2; 18:3, n-3) by the enzyme delta-6-desaturase, that removes two hydrogen (H) ato ...

and alpha-linolenic acid. ''Tisochrysis lutea'' contains betain lipids and

phospholipid Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids ty ...

Classification

The haptophytes were first placed in the class Chrysophyceae (golden algae), but ultrastructural data have provided evidence to classify them separately. Both molecular and morphological evidence supports their division into five orders; coccolithophores make up the Isochrysidales and Coccolithales. Very small (2-3μm) uncultured pico-prymnesiophytes are ecologically important. Haptophytes was discussed to be closely related to

cryptomonad The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterio ...

s. Haptophytes are closely related to the SAR clade. Subphylum Haptophytina Cavalier-Smith 2015 aptophyta Hibberd 1976 sensu Ruggerio et al. 2015ref> * Clade Rappemonada Kim et al. 2011 ** Class Rappephyceae Cavalier-Smith 2015 *** Order Rappemonadales **** Family Rappemonadaceae * Clade Haptomonada (Margulis & Schwartz 1998) [Haptophyta Hibberd 1976 emend. Edvardsen & Eikrem 2000; Prymnesiophyta Green & Jordan, 1994; Prymnesiomonada; Prymnesiida Hibberd 1976; Haptophyceae Christensen 1962 ex Silva 1980; Haptomonadida; Patelliferea Cavalier-Smith 1993] ** Class Pavlovophyceae Cavalier-Smith 1986 [Pavlovophycidae Cavalier-Smith 1986] *** Order Pavlovales Green 1976 **** Family Pavlovaceae Green 1976 ** Class Prymnesiophyceae Christensen 1962 emend. Cavalier-Smith 1996 aptophyceae s.s.; Prymnesiophycidae Cavalier-Smith 1986; Coccolithophyceae Casper 1972 ex Rothmaler 1951*** Family † Eoconusphaeraceae Kristan-Tollmann 1988 onusphaeraceae*** Family † Goniolithaceae Deflandre 1957 *** Family †

Lapideacassaceae Lapideacassaceae is a family of haptophytes belonging to the class Prymnesiophyceae. The family Lapideacassaceae accommodate ‘bell-shaped’ to cylindrical nannoliths with body consisting of a single or several vertically elongated calcite ele ...

Black, 1971 *** Family † Microrhabdulaceae Deflandre 1963 *** Family † Nannoconaceae Deflandre 1959 *** Family † Polycyclolithaceae Forchheimer 1972 emend Varol, 1992 *** Family † Lithostromationaceae Deflandre 1959 *** Family † Rhomboasteraceae Bown, 2005 *** Family Braarudosphaeraceae Deflandre 1947 *** Family Ceratolithaceae Norris 1965 emend Young & Bown 2014 riquetrorhabdulaceae Lipps 1969 - cf Young & Bown 2014*** Family Alisphaeraceae Young et al., 2003 *** Family Papposphaeraceae Jordan & Young 1990 emend Andruleit & Young 2010 *** Family Umbellosphaeraceae Young et al., 2003 mbellosphaeroideae*** Order † Discoasterales Hay 1977 **** Family † Discoasteraceae Tan 1927 **** Family † Heliolithaceae Hay & Mohler 1967 **** Family † Sphenolithaceae Deflandre 1952 **** Family † Fasciculithaceae Hay & Mohler 1967 *** Order Phaeocystales Medlin 2000 **** Family Phaeocystaceae Lagerheim 1896 *** Order Prymnesiales Papenfuss 1955 emend. Edvardsen and Eikrem 2000 **** Family Chrysochromulinaceae Edvardsen, Eikrem & Medlin 2011 **** Family Prymnesiaceae Conrad 1926 ex Schmidt 1931 *** Subclass Calcihaptophycidae **** Order Isochrysidales Pascher 1910 rinsiales Young & Bown 1997***** Family † Prinsiaceae Hay & Mohler 1967 emend. Young & Bown, 1997 ***** Family Isochrysidaceae Parke 1949 hrysotilaceae; Marthasteraceae Hay 1977***** Family Noëlaerhabdaceae Jerkovic 1970 emend. Young & Bown, 1997 ephyrocapsaceae Black 1971**** Order † Eiffellithales Rood, Hay & Barnard 1971 (loxolith; imbricating murolith) ***** Family † Chiastozygaceae Rood, Hay & Barnard 1973 hmuellerellaceae Reinhardt, 1965***** Family † Eiffellithaceae Reinhardt 1965 ***** Family † Rhagodiscaceae Hay 1977 **** Order Stephanolithiales Bown & Young 1997 (protolith; non-imbrication murolith) ***** Family Parhabdolithaceae Bown 1987 ***** Family † Stephanolithiaceae Black 1968 emend. Black 1973 **** Order Zygodiscales Young & Bown 1997 repidolithales***** Family Helicosphaeraceae Black 1971 ***** Family Pontosphaeraceae Lemmermann 1908 ***** Family † Zygodiscaceae Hay & Mohler 1967 **** Order

Syracosphaerales Syracosphaerales is an order of algae consisting of three families: * Calciosoleniaceae * Rhabdosphaeraceae * Syracosphaeraceae References Haptophyte orders {{Haptophyte-stub ...

Ostenfeld 1899 emend. Young et al., 2003 habdosphaerales Ostenfeld 1899***** Family Calciosoleniaceae Kamptner 1927 ***** Family

Syracosphaeraceae Syracosphaeraceae is a family of algae consisting of the following genera: * '' Calciopappus'' * '' Caneosphaera'' * '' Coronosphaera'' * '' Deutschlandia'' * '' Lohmannosphaera'' * '' Michaelsarsia'' * '' Ophiaster'' * '' Syracosphaera'' ...

Lohmann, 1902 alopappiaceae Kamptner 1928(caneolith & cyrtolith; murolith) ***** Family

Rhabdosphaeraceae Rhabdosphaeraceae is a family of algae 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. Inclu ...

Haeckel, 1894 (planolith) **** Order † Watznaueriales Bown 1987 (imbricating placolith) ***** Family † Watznaueriaceae Rood, Hay & Barnard 1971 **** Order † Arkhangelskiales Bown & Hampton 1997 ***** Family † Arkhangelskiellaceae Bukry 1969 ***** Family † Kamptneriaceae Bown & Hampton 1997 **** Order † Podorhabdales Rood 1971 iscutales Aubry 2009; Prediscosphaerales Aubry 2009(non-imbricating or radial placolith) ***** Family † Axopodorhabdaceae Wind & Wise 1977 odorhabdaceae Noel 1965***** Family † Biscutaceae Black, 1971 ***** Family † Calyculaceae Noel 1973 ***** Family † Cretarhabdaceae Thierstein 1973 ***** Family † Mazaganellaceae Bown 1987 ***** Family † Prediscosphaeraceae Rood et al., 1971 eflandriaceae Black 1968***** Family † Tubodiscaceae Bown & Rutledge 1997 **** Order Coccolithales Schwartz 1932 occolithophorales***** Family Reticulosphaeraceae Cavalier-Smith 1996 eticulosphaeridae***** Family Calcidiscaceae Young & Bown 1997 ***** Family Coccolithaceae Poche 1913 emend. Young & Bown, 1997 occolithophoraceae***** Family Pleurochrysidaceae Fresnel & Billard 1991 ***** Family Hymenomonadaceae Senn 1900 chrosphaeraceae Schussnig 1930

References

External links

{{Taxonbar, from=Q500531 Algal taxonomy * Bikont phyla