DESCRIPTION OF THE KINGDOM HETEROKONTAE (CAVALIER-SMITH 1986)
| EUKARYA> CHROMALVEOLATA> HETEROKONTAE |
KINGDOM HETEROKONTAE LINKS
| Heterokontae (he-te-ro-KON-tee) is made of two Greek roots that mean “different” (heteros -ἕτερος) and “pole” (kontos – κοντός). The reference is to the two different types of flagella on the typical motile cell. Cavalier-Smith (1986) created Heterokonta to refer to an infrakingdom of taxa with heterodynamic flagella. We use the term at the rank of kingdom and have given it a a plural Latin feminine ending to become Heterokontae. Now, more commonly the literature is using the term stramenopiles for this group. |
| INTRODUCTION TO THE HETEROKONTAE The Kingdom Heterokontae includes those taxa with tubulocristate (text with tooltip) Cristae (crista, sing.) generally refer to folds of the inner membranes of mitochondria. mitochondria that produce the heterokont motile cell, a heterodynamic (text with tooltip) Heterodynamic flagella occur on the same cell but beat with different patterns (e.g. anterior-posterior). cell with paired flagella: one an anteriorly-directed (text with tooltip) An anteriorly-directed flagellum extends in the direction of the motion of the motile cell. The interpretation is that the flagellum functions by pulling the cell. tinsel (text with tooltip) A tinsel flagellum is one that is covered with flagellar hairs and thus appears thicker in light microscopy. Usually, tinsel flagella are anteriorally-directed. flagellum and the other a recurrent or posteriorly-directed whiplash (text with tooltip) (1) A whiplash flagellum is a eukaryotic 9+2 flagellum with few or no flagellar hairs or scales. These may be directed anteriorly or posteriorly.<br>(2) A whiplash flagellum is free of hair-like mastigonemes and usually is trailing or posteriorly-directed. flagellum. There are variations on that theme; however, when there are pairs of basal bodies (text with tooltip) Basal bodies (also called kinetosomes) are organelles that are not membrane-bound. All eukaryotic flagella (also called undulipodia) are underlain or attached to the cell by the basal body. The basal body is a microtubular structure with the general formula 9(3)+0. They are indistinguishable from centrioles. , they are anchored by four flagellar roots (text with tooltip) Flagellar roots are microtubular structures that arise from the basal bodies and elaborate to the inside of the cell. They may connect to the nucleus (as part of a karyomastigont) or course their way into the cell such that they form other structures like axostyles. (Patterson 1999). Some of these taxa are variously called Stamenopiles (Patterson 1989) or Chromista (Cavalier-Smith 1989). They are in a coherent clade of crown eukaryotes of ten phyla in this system. They are recognized as a natural group joined by tripartite tubular hairs (text with tooltip) Tripartite Tubular Hairs are mastigonemes (flagellar hairs) that occur on the anteriorly-directed flagellum. They seem to reverse the thrust of the flagellum. on their flagella as a major synapomorphy, although some taxa have secondarily lost this character (Patterson 1989 and 1999; Andersen 1991; Leipe et al. 1994; Saunders et al. 1995; Silberman et al. 1996; and Cavalier-Smith 1989). We included Opalinota because of ribosomal RNA similarities. Indeed, we have used the phylogeny of Sogin and Patterson (Tree of Life Project) to address the questions of the opalinids and other relationships in the kingdom. The kingdom varies from multiflagellated unicells to large (many meters long) multicellular kelps, a diversity in form that rivals that of the Plant Kingdom. Cavalier-Smith (1986) united most of the photosynthetic heterokonts into a single phylum, the Ochrophyta, a taxon adopted by Graham and Wilcox (2000) to include the diatoms, raphidiophytes, chrysophytes, eustigs, silicoflagellates, xanthophytes, and phaeophytes. Although these taxa do seem to be part of the same clade, we interpret them as related within the same subkingdom because of the enormous variation between these groups. Until recently the heterokonts were among the groups included in the “crown eukaryotes”; however, work summarized by Baldauf (2003) presents a very different picture of eukaryote evolution. New phylogenies based on many molecular and ultrastructural relationships indicate that the eukaryotes occupy eight great “clades” called supergroups, one of which is the heterokonts. In her synthesis, though, Baldauf (2003) has the cryptomonads and haptomonads associated with the base of the typical heterokont – alveolate line in a sister group relationship. Harper et al. (2005) use a 6-protein phylogeny of eukaryote taxa and provide strong evidence that the Heterokonts are part of a larger clade (alveolates+heterokonts) and have a weak association with the cryptomonad+haptomonad clade. Keeling (2004) also suggests the same relationship in a supergroup called the chromalveolates [formalized to Chromalveolata]. Recent work on the heterokonts (also called stramenopiles) confirms the monophyly of the photosynthetic phyla (labeled clade Oc in Figure 1). These seem to be clustered into three clades (after Yang et al. 2012): SI (Xanthophyta, Phaeophyta, and Raphidiophyta), SII (Eustigmatophyta, Chrysophyta, and Pinguiophyta), and SIII (Silicoflagellata, Actinophryida, and Bacillariophyta). Among the non-photosynthetic taxa, Oomycota is the sister to the Ochrophyta clade. Opalinata is basal in the group and lacks characteristics of the heterokont flagella (e.g. tripartite tubular hairs on one of the flagella). |
FIGURE 1. A phylogenetic tree of the phyla of the Heterokontae. Photosynthetic taxa in the clade labeled Oc (Ochrophyta) are clustered into three clades. The topology of the cladogram is a summary of Andersen (2004), Adl et al. (2005), Brown and Sorhannus (2010), Walker et al. (2011), and Yang et al. (2012).
| PHYLA OF THE KINGDOM HETEROKONTAE |
OPALINATA (Wenyon 1926)
LABYRINTHOMORPHA (Levine et al. 1980)
BICOSOECIDA (Grasse 1926)
OOMYCOTA (Winter 1879)
CHRYSOPHYTA (Pascher 1914)
SILICOFLAGELLATA (Borgert 1890)
ACTINOPHRYIDA (Claus 1874)
RAPHIDIOPHYTA (Chadefaud 1950)
XANTHOPHYTA (Allorge ex Fritsch 1935)
EUSTIGMATOPHYTA (Hibberd & Leedale 1970)
PHAEOPHYTA (Kjellman 1891)
BACILLARIOPHYTA (Haeckel 1878)
| LITERATURE CITED Adl, S. M., A. G. B. Simpson, M. A. Farmer, R. A. Andersen, O. R. Anderson, J. R. Barta, S. S. Bowser, G. Brugerolle, R. A. Fensome, S. Fredericq, T. Y. James, S. Karpov, P. Kugrens, J. Krug, C. E. Lane, L. A. Lewis, J. Lodge, D. H. Lynn, D. G. Mann, R. M. McCourt, L. Mendoza, O. Moestrup, S. E. Mozley-Standridge, T. A. Nerad, C. A. Shearer, A. V. Smirnov, F. W. Spiegel, and M. F. J. R. Taylor. 2005. The new higher level classification of eukaryotes with emphasis on the taxonomy of protists. Journal of Eukaryotic Microbiology. 52(5):399-451. Allorge, P. 1930. Heterocontes ou Xanthophycees? Rev. Algol. 5: 230. Andersen, R. A. 1991. The cytoskeleton of chromophyte algae. Protoplasma. 164: 143-159. Andersen R. A. 2004a. Biology and systematics of heterokont and haptophyte algae. American Journal of Botany. 91(10): 1508-1508. [15,L] Brown, J. W. and U. Sorhannus. 2010. 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Patterson, D. J. 1999. The diversity of eukaryotes. American Naturalist. 154 (Suppl.): S96–S124. Saunders, G. W., D. Potter, M. P. Paskind, and R. A. Andersen. 1995. Cladistic analyses of combined traditional and molecular data sets reveal an algal lineage. Proceedings of the National Academy of Sciences. USA. 92: 244–248. Silberman, J.D., M.L. Sogin, D.D. Leipe, and C.G. Clark. 1996. Human parasite finds taxonomic home. Nature 380: 398. Sogin, M. L. and D. J. Patterson. 1995. Stramenopiles. Version 01 January 1995 (under construction). http://tolweb.org/Stramenopiles/2380/1995.01.01 In: The Tree of Life Web Project, http://tolweb.org/ Walker, G., R. G. Dorrell, A. Schlacht, and J. B. Dacks. 2011. Eukaryotic systematics: a 2011 user’s guide for cell biologists and parasitologists. Parasitology. 138: 1-26. Wenyon, C. M. 1926. Protozoology. Wm. Wood and Co. New York. pp.1563. Winter, G. 1879. Über ein natürliches System der Thallophyten. Hedwig a 1879. pt.1: 1–12. Yang, E. C., G. H. Boo, H. J. Kim, S. M. Cho, S. M. Boo, R. A. Andersen, and H. S. Yoon. 2012. Supermatrix data highlight the phylogenetic relationships of photosynthetic stramenopiles. Protist. 163: 217-231. [C] |
| By Jack R. Holt. Last revised: 02/23/2014 |
