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For Heterokontophyta sensu van den Hoek et al., 1978, see Ochrophyta.
Pacific rockweed, Olympic National Park, USA.jpg
Pacific rockweed, Fucus distichus, in Olympic National Park
Scientific classification
Domain: Eukarya
(unranked): Sar
Kingdom: Chromalveolata
Phylum: Heterokonta
Cavalier-Smith, 1986[1]
Typical classes

Colored groups (alga-like)

Colorless groups


  • Stramenopiles Patterson, 1989[2]
  • Straminopiles Vørs, 1993[3][4]
  • Heterokontophyta van den Hoek et al., 1995[5]
  • Stramenopila Alexopoulos et al., 1996[6]
  • Straminipila Dick, 2001[7]
  • Stramenipila Dick, 2001, orth. var.[8]

The heterokonts or stramenopiles (formally, Heterokonta or Stramenopiles) are a major line of eukaryotes[9][10] currently containing more than 25,000 known species.[11] Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which are a primary component of plankton. Other notable members of the Stramenopiles include the (generally parasitic) oomycetes, including Phytophthora of Irish potato famine infamy and Pythium which causes seed rot and damping off.

The name "heterokont" also refers to the type of motile life cycle stage, in which the flagellate cells possess two differently shaped flagella (see zoospore).




Most basal heterokonts are colorless. This suggests that they diverged before the acquisition of chloroplasts within the group. However, fucoxanthin-containing chloroplasts are also found among the haptophytes. These two groups may have a common ancestry, and possibly also a common phylogenetic history with cryptomonads, being grouped by some authors in Chromista. This may be interpreted as suggesting that the ancestral heterokont was an alga, and all colorless groups arose through loss of the secondary endosymbiont and its chloroplast.

Motile cells[edit]

Schematic drawing of Cafeteria roenbergensis (a bicosoecid) with two heterokont flagella: an anterior straminipilous and a posterior smooth.

Many heterokonts are unicellular flagellates, and most others produce flagellate cells at some point in their life-cycle, for instance as gametes or zoospores. The name heterokont refers to the characteristic form of these cells, which typically have two unequal flagella. The anterior straminipilous flagellum is covered with one or two rows of lateral bristles or mastigonemes, which are tripartite (with three regions each), while the posterior flagellum is whiplike, smooth, and usually shorter, or sometimes reduced to a basal body. The flagella are inserted subapically or laterally, and are usually supported by four microtubule roots in a distinctive pattern.




Division Chrysophyta

Class Chrysophyceae (golden algae)
Class Bacillariophyceae (diatoms)

Division Phaeophyta (brown algae)




Some sources divide the heterokonts into the autotrophic Ochrophyta and heterotrophic Bigyra and Pseudofungi.[12] However, some modifications to these classifications have been suggested.



Some examples of classification of the heterokonts.

Cavalier-Smith & Chao (2006)[edit]

Classification according to Cavalier-Smith & Chao, 2006:[14]

Adl et al. (2012)[edit]

Classification according to Adl et al., 2012:[15]



The origin of the name stramenopile is explained by David (2002)[4] and Adl et al. (2005):[16]

Regarding the spelling of stramenopile, it was originally spelled stramenopile. The Latin word for ‘‘straw’’ is straˉmiˇneˇus (the macron ˉ indicates long vowels, while the breve ˇ indicates short vowels), -a, -um, adj. [stramen], made of straw—thus, it should have been spelled straminopile or straminipile (these corrections are based on the fact that the genitive of stramen required for the correct formation of a compound is ‘‘straminis’’, and that the connective used since both parts are latin is ‘‘i’’). However, Patterson (1989) clearly stated that this is a common name (hence, lower case, not capitalized) and, as a common name, it can be spelled as Patterson chooses. If he had stipulated that the name was a formal name, governed by rules of nomenclature, then his spelling would have been an orthogonal mutation and one would simply correct the spelling in subsequent publications (e.g. Straminopiles). But, it was not Patterson’s desire to use the term in a formal sense. Thus, if we use it in a formal sense, it must be formally described (and in addition, in Latin, if it is to be used botanically). However, and here is the strange part of this, many people liked the name, but wanted it to be used formally. So they capitalized the ﬁrst letter, and made it Stramenopiles; others corrected the Latin spelling to Straminopiles.


  3. ^ Vørs, N (1993). "Marine heterotrophic amoebae, flagellates and heliozoa from Belize (Central America) and Tenerife". Journal of Eukaryotic Microbiology 40: 272–287. doi:10.1111/j.1550-7408.1993.tb04917.x. 
  4. ^ a b David, J. C. (2002). A preliminary catalogue of the names of fungi above the rank of order. Constancea 83: 1–30, [1].
  7. ^ Dick, M. W. (2001). Straminipilous fungi. Dordrecht, the Netherlands: Kluwer Academic Publishers. 670 p., [2].
  11. ^ Chapman, A. D. (2009). Numbers of living species in Australia and the world.
  12. ^ Riisberg I, Orr RJ, Kluge R et al. (May 2009). "Seven gene phylogeny of heterokonts". Protist 160 (2): 191–204. doi:10.1016/j.protis.2008.11.004. PMID 19213601. 
  14. ^ Cavalier-Smith, T; Chao, E. E. (2006). "Phylogeny and megasystematics of phagotrophic heterokonts (kingdom Chromista)". Journal of Molecular Evolution 62 (4): 388–420. doi:10.1007/s00239-004-0353-8. PMID 16557340.  Supplementary material [3].

External links[edit]