Haptophyte

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Haptophytes
Coccolithophore (Emiliania huxleyi)
Scientific classification
Domain: Eukaryota Kingdom: Chromalveolata Phylum: Haptophyta Hibberd 1976
Orders
Class Pavlovophyceae    Pavlovales Class Prymnesiophyceae    Prymnesiales    Phaeocystales    Isochrysidales    Coccolithales

The haptophytes, classed either as the Prymnesiophyta or Haptophyta, are a phylum of algae. The chloroplasts are pigmented similarly to those of the heterokonts, such as golden algae, 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 endosymbionts.

The cells typically have two slightly unequal flagella, 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 hapsis, touch, and nema, thread. The mitochondria have tubular cristae.

Haptophytes are economical important as Pavlova lutheri and Isochrysis sp. are widely used in the aquaculture industries.

The best-known haptophytes are coccolithophores, which have an exoskeleton of calcareous plates called coccoliths. Coccolithophores are some of the most abundant marine phytoplankton, especially in the open ocean and are extremely abundant as microfossils. Other planktonic haptophytes of note include Chrysochromulina and Prymnesium, which periodically form toxic marine algal blooms, and Phaeocystis blooms of which can produce unpleasant foam which often accumulates on beaches. Both molecular and morphological evidence supports their division into five orders; coccolithophores make up the Isochrysidales and Coccolithales.

[edit] References

R.A. Anderson. American Journal of Botany 91(10): 1508-1522. 2004. Biology and Systematics of Heterokont and Haptophyte Algae.