Dictyochophyceae
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| PC Silva , 1980 |
The Dictyochophyceae are a taxon of unicellular organisms from the stramenopile group (also called Heterokonta or Chromista).
features
All representatives are single-celled, rarely they form aggregates or cell colonies. Dictyochophyceae, like the related groups (known as the Taxon Diatomista), do not have a cell wall ; sometimes the cells have a covering of cellulose flakes . Many representatives are flagellated, there is then always only one functional flagellum , which acts as a dragging flagellum (i.e. starts at the front and pulls the cell), this is covered with three-part cilia ( mastigonema ). The anchoring of the kinetosome of the flagellum is characteristic of the other kinetosome , which is partially reduced, an anchoring from microtubules is missing, as is a root called a rhizoplast; as a result, the kinetosome sits almost directly on the nucleus. The kinetosome, occasionally a rudiment of the second scourge (typical of the heteroconta named after it) are present. Some representatives have a cytoskeleton made of amorphous silicon dioxide , others are naked and often movable like an amoeba, many can protrude pseudopodia. The chloroplasts are divided by a belt-shaped single pyrenoid . They are yellow-green in color, pigments are the chlorophylls a and c1 and c2, as well as carotenoids (from the group of xanthophylls ), including fucoxanthin, diatoxanthin and diadinoxanthin . With some representatives the plastids are partially regressed and colorless, they feed heterotrophically, the others are purely phototrophic or mixotrophic . Eye spots are always missing.
The group is very well secured by morphological and molecular (genetic) characteristics, their togetherness has been known since the early 1990s. The Pelagophyceae are closely related and possible sister groups .
Systematics
Within the class of Dictyochophyceae, three orders are distinguished:
- Dictyochales with a silicate skeleton at least in one life stage, always with chloroplasts. marine.
- Pedinellales : flagellates, naked, with organic scales or lorica called cell envelope; Plastids present or absent, often with griffin tentacles. marine and limnic.
- Rhizochromulinales: vegetative cells are amoeboid, zoospores flagellated; Plastids present. The only species is Rhizochromulina marina .
literature
- Sina M. Adl, Alastair GB Simpson, Christopher E. Lane, Julius Lukeš, David Bass, Samuel S. Bowser, Matthew W. Brown, Fabien Burki, Micah Dunthorn, Vladimir Hampl, Aaron Heiss, Mona Hoppenrath, Enrique Lara, Line le Gall, Denis H. Lynn, Hilary McManus, Edward AD Mitchell, Sharon E. Mozley-Stanridge, Laura W. Parfrey, Jan Pawlowski, Sonja Rueckert, Laura Shadwick, Conrad L. Schoch, Alexey Smirnov, Frederick W. Spiegel (2019) : The Revised Classification of Eukaryotes. Journal of Eukaryotic Microbiology 59 (5): 4-119. doi: 10.1111 / j.1550-7408.2012.00644.x (open access)
- Romain Derelle, Purificación López-García, Hélène Timpano, David Moreira (2016): A Phylogenomic Framework to Study the Diversity and Evolution of Stramenopiles (= Heterokonts). Molecular Biology and Evolution 33 (11): 2890-2898. doi: 10.1093 / molbev / msw168 (open access).
- Thomas Cavalier-Smith (2018): Kingdom Chromista and its eight phyla: a new synthesis emphasizing periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences. Protoplasm 255: 297-357. doi: 10.1007 / s00709-017-1147-3
- Robert A. Andersen (2004): Biology and Systematics of the Heterokont and Haptophyte Algae. American Journal of Botany 91 (10): 1508-1522.
- GW Saunders, D. Potter, MP Paskind, RA Andersen (1995): Cladistic analyzes of combined traditional and molecular data sets reveal an algal lineage. PNAS Proceedings of the National Academy of Sciences USA 92 (1): 244-248. doi: 10.1073 / pnas.92.1.244 . (open access).
Web links
- Class Dictyochophyceae in Guiry, MD & Guiry, GM 2019. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway (www.algaebase.org). accessed on May 15, 2019.