The haptophytes, classified either as the Haptophytina, Haptophyta or Prymnesiophyta (named for Prymnesium), are a clade of algae that produce minerals.
The names Haptophyceae or Prymnesiophyceae are sometimes used instead.
Characteristics
The
are pigmented similarly to those of the
,
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 algae endosymbionts. Haptophyte chloroplasts contain chlorophylls
Chlorophyll a, c
1, and c
2 but lack chlorophyll b. For carotenoids, they have
beta-carotene, alpha-, and gamma- carotenes. Like
diatoms and
brown algae, they have also
fucoxanthin, an oxidized isoprenoid derivative that is likely the most important driver of their brownish-yellow color.
The cells typically have two slightly unequal flagellum, 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 and in its use. The name comes from the Greek language hapsis, touch, and nema, round thread. The mitochondrion have tubular .
Most haptophytes reportedly produce chrysolaminarin rather than starch as their major storage polysaccharide, but some Pavlovaceae produce paramylon.
Significance
The best-known haptophytes are
, which make up 673 of the 762 described haptophyte species,
and have an exoskeleton of calcareous plates called
. Coccolithophores are some of the most abundant marine
phytoplankton, especially in the open ocean, and are extremely abundant as microfossils, forming
chalk deposits. Other planktonic haptophytes of note include
Chrysochromulina and
Prymnesium, which periodically form toxic marine
, and
Phaeocystis, 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 and shrimp larvae. They contain a large amount of polyunsaturated fatty acids such as docosahexaenoic acid (DHA), stearidonic acid and alpha-linolenic acid.
Classification
The haptophytes were first placed in the class Chrysophyceae (golden algae), but ultrastructural data have provided evidence to classify them separately.
Haptophytes was discussed to be closely related to .
Haptophytes are closely related to the SAR supergroup clade.
Subphylum Haptophytina Cavalier-Smith 2015 Haptophyta
-
Clade Rappemonada Kim et al. 2011
-
Clade Haptomonada (Margulis & Schwartz 1998) Haptophyta
-
Class Pavlovophyceae Cavalier-Smith 1986 Pavlovophycidae
-
Class Prymnesiophyceae Christensen 1962 emend. Cavalier-Smith 1996 Haptophyceae
-
Family †Eoconusphaeraceae Kristan-Tollmann 1988 Conusphaeraceae
-
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
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Family Ceratolithaceae Norris 1965 emend Young & Bown 2014 Triquetrorhabdulaceae
-
Family Alisphaeraceae Young et al., 2003
-
Family Papposphaeraceae Jordan & Young 1990 emend Andruleit & Young 2010
-
Family Umbellosphaeraceae Young et al., 2003 Umbellosphaeroideae
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Order †Discoasterales Hay 1977
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Order Phaeocystales Medlin 2000
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Order Prymnesiales Papenfuss 1955 emend. Edvardsen and Eikrem 2000
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Family Chrysochromulinaceae Edvardsen, Eikrem & Medlin 2011
-
Family Prymnesiaceae Conrad 1926 ex Schmidt 1931
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Subclass Calcihaptophycidae
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Order Isochrysidales Pascher 1910 Prinsiales
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Family †Prinsiaceae Hay & Mohler 1967 emend. Young & Bown, 1997
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Family Isochrysidaceae Parke 1949 Chrysotilaceae;
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Family Noëlaerhabdaceae Jerkovic 1970 emend. Young & Bown, 1997 Gephyrocapsaceae
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Order †Eiffellithales Rood, Hay & Barnard 1971 (loxolith; imbricating murolith)
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Order Stephanolithiales Bown & Young 1997 (protolith; non-imbrication murolith)
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Family Parhabdolithaceae Bown 1987
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Family †Stephanolithiaceae Black 1968 emend. Black 1973
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Order Zygodiscales Young & Bown 1997 Crepidolithales
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Order Syracosphaerales Ostenfeld 1899 emend. Young et al., 2003 Rhabdosphaerales
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Family Calciosoleniaceae Kamptner 1927
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Family Syracosphaeraceae Lohmann, 1902 Halopappiaceae (caneolith & cyrtolith; murolith)
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Family Rhabdosphaeraceae Haeckel, 1894 (planolith)
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Order †Watznaueriales Bown 1987 (imbricating placolith)
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Order †Arkhangelskiales Bown & Hampton 1997
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Family †Arkhangelskiellaceae Bukry 1969
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Family †Kamptneriaceae Bown & Hampton 1997
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Order †Podorhabdales Rood 1971 Biscutales (non-imbricating or radial placolith)
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Order Coccolithales Schwartz 1932 Coccolithophorales
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Family Reticulosphaeraceae Cavalier-Smith 1996 Reticulosphaeridae
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Family Calcidiscaceae Young & Bown 1997
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Family Coccolithaceae Poche 1913 emend. Young & Bown, 1997 Coccolithophoraceae
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Family Pleurochrysidaceae Fresnel & Billard 1991
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Family Hymenomonadaceae Senn 1900 Ochrosphaeraceae
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