Overview
Order Centrales is a traditional, subdivision of the heterokont algae known as diatoms1][2]. [3] The order is named for the shape of the cell walls (or valves or frustules) of centric diatoms, which are circular or ellipsoid in valve view. The valves often bear radially symmetrical ornamental patterns that can appear as dots when viewed with an optical microscope. Some also bear spines on their valves, which may either increase cell surface area and reduce sinking, or act as a deterrant to zooplankton grazers. Unlike pennate diatoms, centric diatoms never have a raphe.
In terms of cell cycle, vegetative cells are diploid and undergo mitosisduring normal cell division. In sexual species, oogamous meiosis produces haploid gametes, either ova or sperm cells. These fuse to produce a zygote which expands in size to develop into an auxospore from which full-size vegetative cells are produced.
In some taxonomy schemes[2], the centric diatoms are known instead as Order Coscinodiscophyceae. And in some schemes as order Biddulphiales [4]. However, diatom taxonomy is changing due to the development of new molecular and genetical analysis tools[3].
Taxonomy
The Class Coscinodiscophyceae is further organized into finer groupings including:
- Subclass (8): Biddulphiophycidae · Chaetocerotophycidae · Corethrophycidae · Coscinodiscophycidae · Cymatosirophycidae · Lithodesmiophycidae · Rhizosoleniophycidae · Thalassiosirophycidae
- Order (22): Anaulales · Arachnoidiscales · Asterolamprales · Aulacoseirales · Biddulphiales · Chaetocerotales · Chrysanthemodiscales · Corethrales · Coscinodiscales · Cymatosirales · Ethmodiscales · Hemiaulales · Leptocylindrales · Lithodesmiales · Melosirales · Orthoseirales · Paraliales · Rhizosoleniales · Stictocyclales· Stictodiscales · Thalassiosirales · Triceratiales
- Species: ZipcodeZoo has pages for 2,997 species and subspecies in the Class Coscinodiscophyceae.
Orders
Anaulales
Arachnoidiscales
Asterolamprales
Aulacoseirales
Biddulphiales
Chaetocerotales
Chrysanthemodiscales
Corethrales
Coscinodiscales
Cymatosirales
Ethmodiscales
Hemiaulales
Leptocylindrales
Lithodesmiales
Melosirales
Orthoseirales
Paraliales
Rhizosoleniales
Stictocyclales
Stictodiscales
Thalassiosirales
Triceratiales
At least 249 species and subspecies belong to the Order Triceratiales.
More info about the Order Triceratiales may be found here.
References
- ^ Hoek, C. van den, Mann, D. G. and Jahns, H. M. (1995). Algae : An introduction to phycology, Cambridge University Press, UK.
- ^ a b Round, F. E. and Crawford, R. M. (1990). The Diatoms. Biology and Morphology of the Genera, Cambridge University Press, UK.
- ^ a b Williams, D. M., Kociolek, J. P., (2007). Pursuit of a natural classification of diatoms: History, monophyly and the rejection of paraphyletic taxa, European Journalof Phycology, 42:3, 313-319.
- ^ Tomas, C. R., Hasle G. R., Syvertsen, E. E., Steidinger, K. A., Tangen, K., Throndsen, J., Heimdal, B. R., (1997). Identifying Marine Phytoplankton, Academic Press.
Sources
- The distribution map on the Distribution tab comes from the Global Biodiversity Information Facility and is used with permission.
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