From Self-sufficiency
Jump to: navigation, search
Clockwise from top-left: a haptophyte, some diatoms, a water mold, a cryptomonad, and Macrocystis, a phaeophyte
Scientific classification
Domain: Eukarya
(unranked) Bikonta
(unranked): Corticata
Kingdom: Chromalveolata*

Chromalveolata is a eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first put forward in 1981. Chromalveolata was proposed to represent the result of a single secondary endosymbiosis between a line descending from a bikont and a red alga[1] that became the progenitor of chlorophyll c containing plastids. In a major classification produced in 2005, Chromalveolata was regarded as one of the six major groups within the eukaryotes.[2] However this has been increasingly challenged. Thus two papers published in 2008 have phylogenetic trees in which the chromalveolates are split up.[3][4]

Groups and classification

Historically, many chromalveolates were considered plants, because of their cell walls, photosynthetic ability, and in some cases their morphological resemblance to the land plants (Embryophyta). However, when the five-kingdom system took prevalence over the animal-plant dichotomy, most chromalveolates were put into the kingdom Protista, with the water molds and slime nets put into the kingdom Fungi, and the brown algae staying in the plant kingdom.

In 2005, in a classification reflecting the consensus at the time, the Chromalveolata were regarded as one of the six major clades of eukaryotes.[2] Although not given a formal taxonomic status in this classification, elsewhere the group has been treated as a Kingdom. The Chromalveolata were divided into four major subgroups:

Other groups which may be included within, or related to, chromalveolates, are:

Though several groups, such as the ciliates and the water molds, have lost the ability to photosynthesize, most are autotrophic. All photosynthetic chromalveolates use chlorophylls a and c, and many use accessory pigments. Chromalveolates share similar glyceraldehyde 3-phosphate dehydrogenase proteins.[6]

However, as early as 2005, doubts were being expressed as to whether the Chromalveolata was monophyletic,[7] and a review in 2006 noted the lack of evidence for several of the supposed six major eukaryote groups, including the Chromalveolata.[8]. As of 2010 there seems to be an emerging consensus that the group is not monophyletic. The four original subgroups fall into two categories, one comprising the Cryptophyta and the Haptophyta, the other the Stramenopiles and the Alveolata.[3][4]


Analyses in 2007 and 2008 agree that the Stramenopiles and the Alveolata are related, forming a reduced chromalveolate clade.


The Haptophyta and Cryptophyta are related in these analyses,[3][4] forming a clade which has been called 'Hacrobia'.

Position of SAR and Hacrobia

The Hacrobia appear to be more closely related to the Archaeplastida (plants in the very broad sense), being a sister group in one analysis,[3] and actually nested inside this group in another.[4] (Earlier, Cavalier-Smith had suggested a clade called Corticata for the grouping of all the chromalveolates and the Archaeplastida.[9]) The SAR supergroup and the Archaeplastida/Hacrobia combination are grouped in the bikonts, which all appear to descend from a heterotrophic eukaryote with two flagella.


Chromalveolates, unlike other groups with multicellular representatives, do not have very many common morphological characteristics. Each major subgroup has certain unique features, including the alveoli of the Alveolata, the haptonema of the Haptophyta, the ejectisome of the Crytophyta, and the two different flagella of the Heterokontophyta. However, none of these features are present in all of the groups.

The only common chromalveolate features are these:

  • The shared origin of chloroplasts, as mentioned above
  • Presence of cellulose in most cell walls

Since this is such a diverse group, it is difficult to summarize shared chromalveolate characteristics.

Ecological role

Many chromalveolates affect our ecosystem in enormous ways. Some of these organisms can be very harmful. Dinoflagellates produce red tides which can devastate fish populations and intoxicate oyster harvests. Apicomplexans are some of the most successful specific parasites to animals. Water molds cause several plant diseases. In fact, it was a water mold, Phytophthora infestans, that caused the Irish potato famine.

However, many chromalveolates are vital members of our ecosystem. Diatoms are one of the major photosynthetic producers, and as such produce much of the oxygen we breathe, and also take in much of the carbon dioxide from the atmosphere. Brown algae, most specifically kelps, create underwater "forest" habitats for many marine creatures, and provide a large portion of the diet of coastal communities.

Chromalveolates also provide many products that we use. The algin in brown algae is used as a food thickener, most famously in ice cream. The siliceous shells of diatoms have many uses, such as in reflective paint, in toothpaste, or as a filter, in what is known as diatomaceous earth.


Cite error: Invalid <references> tag; parameter "group" is allowed only.

Use <references />, or <references group="..." />

External links

ar:أسناخ صبغية

ca:Cromalveolat cs:Chromalveolata de:Chromalveolata et:Kromalveolaadid es:Chromalveolata fr:Chromalveolata ga:Chromalveolata ko:크로말베올라타 id:Chromalveolata it:Chromalveolata nl:Chromalveolata ja:クロムアルベオラータ pl:Chromalveolata pt:Chromalveolata simple:Chromalveolate sr:Chromalveolata fi:Chromalveolata sv:Chromista th:โครมาลวีโอลาตา

  1. Keeling PJ (2009). "Chromalveolates and the evolution of plastids by secondary endosymbiosis". J. Eukaryot. Microbiol. 56 (1): 1–8. doi:10.1111/j.1550-7408.2008.00371.x. PMID 19335769. 
  2. 2.0 2.1 Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  3. 3.0 3.1 3.2 3.3 Burki, Fabien; Shalchian-Tabrizi, Kamran & Pawlowski, Jan (2008). "Phylogenomics reveals a new 'megagroup' including most photosynthetic eukaryotes". Biology Letters. 4 (4): 366–369. doi:10.1098/rsbl.2008.0224. PMC 2610160Freely accessible. PMID 18522922. 
  4. 4.0 4.1 4.2 4.3 Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  5. Shalchian-Tabrizi K, Eikrem W, Klaveness D, Vaulot D, Minge M, Le Gall F, Romari K, Throndsen J, Botnen A, Massana R, Thomsen H, Jakobsen K (2006). "Telonemia, a new protist phylum with affinity to chromist lineages". Proc Biol Sci. 273 (1595): 1833–42. doi:10.1098/rspb.2006.3515. PMC 1634789Freely accessible. PMID 16790418. 
  6. Takishita K, Yamaguchi H, Maruyama T, Inagaki Y (2009). "A hypothesis for the evolution of nuclear-encoded, plastid-targeted glyceraldehyde-3-phosphate dehydrogenase genes in "chromalveolate" members". PLoS ONE. 4 (3): e4737. doi:10.1371/journal.pone.0004737. PMC 2649427Freely accessible. PMID 19270733. 
  7. Harper, J. T., Waanders, E. & Keeling, P. J. 2005. On the monophyly of chromalveolates using a six-protein phylogeny of eukaryotes. Int. J. System. Evol. Microbiol., 55, 487-496. [1]
  8. Laura Wegener Parfrey, Erika Barbero, Elyse Lasser, Micah Dunthorn, Debashish Bhattacharya, David J Patterson, and Laura A Katz (2006 December). "Evaluating Support for the Current Classification of Eukaryotic Diversity". PLoS Genet. 2 (12): e220. doi:10.1371/journal.pgen.0020220. PMC 1713255Freely accessible. PMID 17194223.  Check date values in: |date= (help)
  9. Cavalier-Smith, T (2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". International journal of systematic and evolutionary microbiology. 52 (Pt 2): 297–354. PMID 11931142.  edit