Ditylum brightwellii

General Close


(diatoms) Having radial symmetry, i.e., cell is shaped like a coin or a tuna can or a soup can.

Shape Triangular prism
Size Length 40 - 300 μm, diameter 14 - 120 μm
Colour Yellow-brown
Connection Central Close


In some diatoms, "closed or solid structures projecting from the cell wall;" in dinoflagellates, solid projections that usually taper to a point.

Covering Silica Close


In diatoms, the hard and porous silica cell wall (Horner 2002).



(plural: flagella) A tail-like projection that sticks out from the cell body and enables movement.



An organelle in the cell that contains the cell pigments (Horner 2002). This is where photosynthesis occurs. A chloroplast is a specialized chromatophore.

Numerous and small
Lifestyle Close


The chemical process by which light energy, water and carbon dioxide are combined to produce oxygen and organic compounds. Photoautotrophic organisms (plants and algae) use this reaction to produce their own food.

. Sexual/asexual. Close

Resting spore

In diatoms, a cell that requires a dormancy period prior to germination and can survive for several years; usually developed to survive adverse conditions. They are commonly observed in centric but not pennate diatoms. The morphology of the spore may be similar or different from a vegetative cell; they usually have heavily silicified walls and are rich in storage products (Horner 2002).

and microspores present.


A rapid increase or accumulation of algal populations in an aquatic system. This will likely involve one or a few dominant phytoplankton species. This follows seasonal patterns (i.e., spring, summer or fall bloom) with dominant species being those that are best adapted to the environmental conditions of that time period. Discolouration of the water may be observed because of the algae's pigmentation. Blooms are often green but may be yellow-brown or red depending on the species present.

May consist of genetically different populations.
Harmful effects None known
Habitat Close


Describing shallow, near-shore areas and the organisms that live there. Refers to shallow marine waters ranging from the low tide mark to the continental shelf. Varying amounts of sunlight penetrate the water, allowing photosynthesis by both phytoplankton and bottom-dwelling organisms. Close proximity to land favours high nutrient content and biological activity (Encyclopedia Britannica 2011).

Geographic Close


Widely distributed; occurring in many parts in the world.

except in polar seas
Seasonal Spring around southern Vancouver Island
Growth Conditions


The dissolved ion content of a body of water. Can be measured in the following units: parts per thousand (PPT or ‰), practical salinity units (PSU), and absolute salinity (g/kg). PPT is measured by weight, denoting the number of parts salt per thousand total parts or a value of 10-3. PSU measures the conductivity of saltwater and compares it in a ratio to a standard KCl solution (because this is a ratio, salinity measured in this way can also be written without units). The newest unit of salinity is absolute salinity, which uses the mass fraction of salt in seawater (g salt per kg seawater) rather than its conductivity (TEOS-20 2010).

26 - 36
Temperature 0 - 29 °C


Ditylum trigonum L. W. Bailey ex L. W. Bailey 1862 Close


A difference in type. In naming species, a heterotypic synonym is one that comes into being when a taxon becomes part of a different taxon. Compare to homotypic.

Ditylum inaequale J. W. Bailey ex L. W. Bailey 1862 (heterotypic)
Triceratium brightwellii T. West 1860 Close


The original name for an organism. In botany, the original published nomenclature from which a new binomial nomenclature is derived for a particular group of organisms (Tindall 1999).

, Close


Expressing the same fundamental type or structure; may or may not be symmetrical (e.g., the two valves of a diatom, where they are the same shape and appearance, but one is bigger than the other). In naming species, a homotypic synonym is one that comes into being when a taxon gets a new name (without being added to an already existing taxon).

(Guiry and Guiry 2011)


Empire Eukaryota
Kingdom Chromista
Subkingdom Chromobiota
Infrakingdom Heterokonta
Phylum Bacillariophyta
Subphylum Bacillariophytina
Class Mediophyceae
Subclass Lithodesmiophycidae
Order Lithodesmiales
Family Lithodesmiaceae
Genus Ditylum
Species D. Brightwellii (T. West) Grunow 1885

(Guiry and Guiry 2011)


Photosynthetic. Reproduces sexually and asexually (Guiry 2011). Resting spores and microspores present (Gran and Angst 1931, Cupp 1943, Hargraves 1982; see Description).


Cells are usually solitary, sometimes in short chains. They are rectangular in Close


In diatoms, the portion of the cell wall between the two valves of a cell; made up of intercalary bands (bands closest to the valves) and connecting bands (bands in the middle of the girdle). In dinoflagellates, the equivalent of a cingulum or transverse furrow (Horner 2002).

view and roughly triangular in Close


In diatoms, the structurally distinct halves of the cell wall (Becker 1996).

view. A large spine extends from the centre of each valve, and is surrounded by a Close


The outline or border that defines the shape of an organism or cell.

ridge. Chains are connected by the large spines. Chloroplasts are small and numerous; Close


(plural: nuclei) In eukaryotic cells, a membrane-bound organelle that contains the cell's genetic information; the nucleus controls the activities of the cell by controlling gene expression.

is central (Cupp 1943). Cells are yellow-brown in colour (Guiry 2011).
Large central spines are Close

Labiate process

In diatoms, a simple slit in the valve wall with two internal lips, one on each side of the slit. They can be useful in identification because they are positioned differently in different species (Horner 2002).

bilabiate processes
; marginal ridge can be a ring of small Close


A natural projection or appendage on an organism.

called Close


In Ditylum and related diatoms, ansulae are the "fringes" seen near the ends of each cell. In SEM, you can see that each ansula is split into two ribbon-like points. A "single element of the fringed marginal ridge of Ditylum, shaped as a ribbon longitudinally split in its medium part" (Hasle and Syvertsen 1996).

, or a continuous membrane with multiple slots (Hasle and Syvertsen 1997). "The girdle zone is very long and not easily distinguishable from the valves. Scale-like Close

Intercalary bands

Girdle bands that are furthest away from the valve (Smithsonian 2011).

intercalary bands
are visible with special treatment. Cell wall is weakly Close


Describing the character (i.e., white, shimmery) or chemical presence silicon dioxide (SiO2) as a component of phytoplankton cell covering.

. Valves are Close


Synonym: perforated. Describing a surface that has many holes. Often used to describe the valve surface of diatom frustules.

- Close


Marked with tiny coloured spots or depressions.

, with areolae becoming more delicate toward the outside. A central area around the spine is structureless. Areolae are in Close


(symmetry) Describing a shape that many axes of symmetry. That is, it does not have a left and right like humans do (bilateral symmetry), but can be divided into equal halves no matter where you place the axis. Some examples of radially symmetrical organisms include sea stars and centric diatoms like Thalassiosira.

rows on valve surface, in Close

Pervalvar axis

The axis through the centre point of the two valves of a frustule. This axis is perpendicular to the valve face.

rows on valve Close


In diatoms, "the part of a valve that extends from the valve face, forming the valve edge." It is visible when the frustule is viewed in girdle view (Spaulding 2010).

. The structure of the intercalary bands is similar but more delicate" (Cupp 1943).
"Resting spores are large, excentric or polar. Valves are like those of the mother cell, primary valve with a long valve mantle and strong spine, secondary valve without a mantle" (Cupp 1943).


Length (pervalvar axis): 40 - 300 μm
Diameter: 14 - 120 μm
Valve areolae or Close


Features that provide support to other structures in the cell.

: 10 in 10 μm
Mantle areolae: 16 - 19 in 10 μm
(Cupp 1943, Kraberg et al. 2010)

Similar species

None. This species can be easily identified by the two large spines on its rectangular body.

Harmful effects

None known.


Neritic (Cupp 1943).


Cosmopolitan except in polar regions (Hasle and Syvertsen 1997).
Blooms during spring around southern Vancouver Island (Ryerson et al. 2006), and during fall around the Bay of Fundy (Martin et al. 2008). Most abundant in spring and summer in Northern European seas, but occasionally present in small numbers throughout the year (Kraberg et al. 2010).
A south temperate species commonly found from the Gulf of California to the eastern Aleutian Islands, Alaska, though never in very large numbers (Cupp 1943).

Growth conditions

Indicative of cooler, Close


Various chemical substances that an organism needs for metabolism (i.e., to live and grow). These are usually taken up from the environment. Some examples include nitrate, phosphate, silica (for diatoms), iron, copper, etc. Some nutrients, like copper, are required for growth, but can also be toxic at high levels.

-rich waters (Hobson and McQuoid 2001). Cells are very sensitive to Close


The shrinking of the protoplasm away from the cell wall of an organism due to water loss from osmosis (when the cell has greater water pressure than its surroundings). This results in gaps between the cell wall and the cell membrane (Spaulding et al. 2010).

(Kraberg et al. 2010).

Environmental Ranges

Depth range (m): 0 - 470
Temperature range (°C): -0.245 - 29.468
Nitrate (μmol L-1): 0.056 - 20.029
Salinity: 25.730 - 36.252
Oxygen (mL L-1): 4.500 - 7.859
Phosphate (μmol L-1): 0.048 - 1.656

Silicic acid

A general term to describe chemical compounds containing silicon, oxygen and hydrogen with a general formula of [SiOx(OH)4-2x]n. Diatoms polymerize silicic acid into biogenic silica to form their frustules (Azam and Chisholm 1976).

(μmol L-1): 0.648 - 35.557
(OBIS 2011, cited in EOL 2011)

Bloom characteristics

Blooms may consist of genetically different populations with distinctly different exposures to light and silicic acid concentrations (Ryerson et al. 2006).


Cupp, E. E. 1943. Marine Plankton Diatoms of the West Coast of North America. University of California Press. Berkeley, California. 238.

Encyclopedia of Life. Ditylum brightwellii (T. West) Grunow. http://www.eol.org/pages/911826. Accessed 10 Jun 2011.

Gran, H. H. and Angst, E. C. 1931. Plankton diatoms of Puget Sound. Publications - Puget Sound Biological Station, University of Washington. 7: 417-519.

Guiry, M. D. (2011). Ditylum brightwellii (T. West) Grunow, 1885. http://www.marinespecies.org/aphia.php?p=taxdetails&id=149023. Accessed 10 Jun 2011.

Guiry, M. D. and Guiry, G. M. 2011. Ditylum brightwellii (T. West) Grunow. http://www.algaebase.org/search/species/detail/?species_id=37800. Accessed 10 Jun 2011.

Hargraves, P. E. 1982. Resting spore formation in the marine diatom Ditylum brightwellii (West) Grun. ex V. H. Proceedings of the Seventh International Diatom Symposium (D.G. Mann, ed). 33-46.

Hasle, G. R. and Syvertsen, E. E. 1997. Marine diatoms. In: Tomas, C. R. (ed.) Identifying marine Phytoplankton. Academic Press, Inc., San Diego, 5-385.

Hobson, L. A. and McQuoid, M. R. 2001. Pelagic diatom assemblages are good indicators of mixed water intrusions into Saanich Inlet, a stratified fjord in Vancouver Island. Marine Geology. 174: 125-138.

Horner, R. A. 2002. A Taxonomic Guide To Some Common Phytoplankton. Biopress Limited, Dorset Press, Dorchester, UK. 200.

Kraberg, A., Baumann, M. and Durselen, C. D. 2010. Coastal Phytoplankton: Photo Guide for Northern European Seas. Verlag Dr. Friedrich Pfeil, Munchen, Germany. 204.

Martin, J. L., Hastey, C. D., LeGresley, M. M. and Page, F. H. 2008. Temporal and Spatial Characteristics of the Diatom Ditylum brightwellii in the Western Isles Region of the Bay of Fundy. Canadian Technical Report of Fisheries and Aquatic Sciences. 2779: 26.

Ocean Biogeographic Information System. Ditylum brightwellii. http://www.iobis.org/mapper/?taxon_id=435735. Accessed 10 Jun 2011.

Ryerson, T. A., Newton, J. A. and Armbrust, E. V. 2006. Spring Bloom Development, Genetic Variation, and Population Succession in the Planktonic Diatom Ditylum brightwellii. Limnology and Oceanography. 51(3): 1249-1261.

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