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

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

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. Included organisms range from unicellular micr ...

. The names Haptophyceae or Prymnesiophyceae are sometimes used instead. This ending implies classification at the

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently ...

rank Rank is the relative position, value, worth, complexity, power, importance, authority, level, etc. of a person or object within a ranking, such as: Level or position in a hierarchical organization * Academic rank * Diplomatic rank * Hierarchy * ...

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 chloroplasts 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, both of which are smooth, and a unique organelle called a ''

haptonema The haptophytes, classified either as the Haptophyta, Haptophytina or Prymnesiophyta (named for '' Prymnesium''), are a clade of algae. The names Haptophyceae or Prymnesiophyceae are sometimes used instead. This ending implies classification at ...

'', 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

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 ...

s, which make up 673 of the 762 described haptophyte species, and have an exoskeleton of calcareous plates called

coccolith Coccoliths are individual plates or scales of calcium carbonate formed by coccolithophores (single-celled phytoplankton such as '' Emiliania huxleyi'') and cover the cell surface arranged in the form of a spherical shell, called a ''coccosphere' ...

s. Coccolithophores are some of the most abundant marine phytoplankton, 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. Ch ...

deposits. Other planktonic haptophytes of note include ''

Chrysochromulina ''Chrysochromulina'' is a genus of haptophytes. This phytoplankton is distributed globally in brackish and marine waters across approximately 60 known species. All ''Chrysochromulina'' species are phototrophic, however some have been shown to ...

'' 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'' encompass ...

s, and ''

Phaeocystis ''Phaeocystis'' is a genus of algae belonging to the Prymnesiophyte class and to the larger division of Haptophyta. It is a widespread marine phytoplankton and can function at a wide range of temperatures ( eurythermal) and salinities (euryhali ...

'', blooms of which can produce unpleasant foam which often accumulates on beaches. Haptophytes are economically important, as species such as '' Pavlova lutheri'' and '' Isochrysis sp.'' are widely used in the aquaculture 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 ...

and shrimp 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-lin ...

(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 ''alpha''-Linolenic acid (ALA), also known as α-Linolenic acid (from Greek ''alpha'' meaning "first" and ''linon'' meaning flax), is an ''n''−3, or omega-3, essential fatty acid. ALA is found in many seeds and oils, including flaxseed, wa ...

. ''Tisochrysis lutea'' contains betain lipids and phospholipids.

Classification

The haptophytes were first placed in the class

Chrysophyceae The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, '' Prymnesium parvum'', whic ...

(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 anteri ...

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 Rappephyceae, or Rappemonads, are a small family of protists first described in 2011, of uncertain phylogenic affinity. It has been discussed as a possible member of a larger clade Haptophyta. This newly identified taxonomic class of phytoplankton ...

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 Prymnesiophyceae is a haptophyte class. Although it was originally described by Casper in 1972, it did not receive a Latin diagnosis (a requirement for valid publication under the International Code of Botanical Nomenclature The ''Internatio ...

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 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 Prymnesiaceae is a family of algae in the clade Haptophyta. It contains toxic microalgae such as ''Prymnesium''. Genera * '' Apistonema'' * '' Chrysocampanula'' * '' Chrysoculter'' * '' Corymbellus'' * '' Haptolina'' * '' Hyalolithus'' * '' Ima ...

Conrad 1926 ex Schmidt 1931 *** Subclass Calcihaptophycidae **** Order

Isochrysidales Isochrysidales is an order of Haptophyceae The haptophytes, classified either as the Haptophyta, Haptophytina or Prymnesiophyta (named for ''Prymnesium''), are a clade of algae. The names Haptophyceae or Prymnesiophyceae are sometimes used i ...

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 Ostenfeld 1899 emend. Young et al., 2003 habdosphaerales Ostenfeld 1899***** Family Calciosoleniaceae Kamptner 1927 ***** Family Syracosphaeraceae Lohmann, 1902 alopappiaceae Kamptner 1928(caneolith & cyrtolith; murolith) ***** Family Rhabdosphaeraceae 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 Coccolithales is an order of Haptophyceae. The Coccolithales has long been considered one of only two orders in the Coccolithophyceae, the other order being the Isochrysidales Isochrysidales is an order of Haptophyceae The haptophytes, cla ...

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