Haptophyte
Algae that produce minerals and include coccolithophores.
The haptophytes, classified either as the Haptophytina, Haptophyta or Prymnesiophyta, are a clade of algae that can produce minerals. Their chloroplasts are pigmented similarly to those of heterokonts, containing chlorophylls a, c1, and c2 but lacking chlorophyll b, and they have fucoxanthin, which contributes to their brownish-yellow color. Cells typically have two slightly unequal smooth flagella and a unique organelle called a haptonema.
- classification
- Clade of algae
- common_names
- Haptophytes, coccolithophores
- key_pigments
- Chlorophylls a, c1, c2; fucoxanthin
- storage_polysaccharide
- Chrysolaminarin (most); paramylon in some Pavlovaceae
- notable_genera
- Coccolithophores, Chrysochromulina, Prymnesium, Phaeocystis
- economic_use
- Aquaculture feed (e.g., Pavlova lutheri, Isochrysis sp.)
Lore & Background
The haptophytes were first placed in the class Chrysophyceae, but ultrastructural data later provided evidence to classify them separately. Both molecular and morphological evidence supports their division into five orders, with coccolithophores making up the Isochrysidales and Coccolithales. Very small uncultured pico-prymnesiophytes are ecologically important. Haptophytes have been discussed as closely related to cryptomonads and are closely related to the SAR clade.
Reader's Guide
Their calcareous plates, called coccoliths, form extensive chalk deposits as microfossils. Other planktonic haptophytes, such as Chrysochromulina and Prymnesium, periodically form toxic marine algal blooms, while Phaeocystis blooms produce unpleasant foam. Economically, species like Pavlova lutheri and Isochrysis sp. are widely used in aquaculture to feed oyster and shrimp larvae, as they contain large amounts of polyunsaturated fatty acids such as docosahexaenoic acid (DHA), stearidonic acid, and alpha-linolenic acid. The phylogenetics of this group has become much better understood, though dispute remains over the most appropriate rank for classification.
Did You Know?
- Haptophytes have a unique organelle called a haptonema, superficially similar to a flagellum but differing in microtubule arrangement and use.
- Some haptophytes, such as Pavlovaceae, produce paramylon instead of chrysolaminarin as their major storage polysaccharide.
- Haptophytes are closely related to the SAR clade.
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