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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 term "Haptophyceae" is sometimes used.[1][2] This ending implies classification at a lower level. However, although the phylogenetics of this group has become much more well understood in recent years, there remains some dispute over which taxon level is most appropriate.

Contents

Characteristics

The chloroplasts are pigmented similarly to those of the heterokonts,[3] 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.

Economic importance

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

Examples and classification

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.

Haptophytes are closely related to cryptomonads.[4]

References

  1. ^ "www.ncbi.nlm.nih.gov". http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=2830&lvl=2.  
  2. ^ Satoh M, Iwamoto K, Suzuki I, Shiraiwa Y (2009). "Cold stress stimulates intracellular calcification by the coccolithophore, Emiliania huxleyi (Haptophyceae) under phosphate-deficient conditions". Mar. Biotechnol. 11 (3): 327–33. doi:10.1007/s10126-008-9147-0. PMID 18830665. http://dx.doi.org/10.1007/s10126-008-9147-0.  
  3. ^ R.A. Anderson. American Journal of Botany 91(10): 1508-1522. 2004. Biology and Systematics of Heterokont and Haptophyte Algae.
  4. ^ Reeb VC, Peglar MT, Yoon HS, et al (April 2009). "Interrelationships of chromalveolates within a broadly sampled tree of photosynthetic protists". Mol. Phylogenet. Evol.. doi:10.1016/j.ympev.2009.04.012. PMID 19398025.  
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Simple English

Haptophytes
Scientific classification
Domain: Eukaryota
Kingdom: Chromalveolata
Phylum: Haptophyta
Hibberd 1976
Orders

Class Pavlovophyceae
   Pavlovales
Class Prymnesiophyceae
   Prymnesiales
   Phaeocystales
   Isochrysidales
   Coccolithales

Haptophytes are a phylum of algae, sometimes called the Prymnesiophyta.[1] All or most of them are single-celled photosynthetic phytoplankton.

The cells typically have two slightly unequal flagella and a unique organelle called a haptonema. This is is superficially similar to a flagellum, but differs in its arrangement of microtubules, and in its use. The name comes from the Greek hapsis = touch, and nema = thread.

Classification

Molecular and morphological evidence places them in five orders; coccolithophores make up the Isochrysidales and Coccolithales. Other groups include phytoplankton which produce the toxic algal blooms.

References

  1. R.A. Anderson. 2004. Biology and systematics of heterokont and haptophyte algae. American Journal of Botany 91: 1508-1522. [1]

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