Pseudo-nitzschia pungens/australis

General Close


(diatoms) A type of diatom that has longitudinal symmetry with valves that are linear or oval shaped. Some pennate diatoms possess a raphe, which allows them to be motile.

Shape Narrow and boat-shaped
Size Length 66 - 144 μm, width 3 - 8 μm
Colour Yellow-brown
Connection Overlapping Close


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

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.

Two, plate-like, one on each side of central plane
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.


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.

Infrequent in local waters. Blooms normally observed off the west coast of Vancouver Island to California.
Harmful effects Produces Close

Domoic acid

(related to ASP) An amino acid produced by some species of diatoms. The neurotoxin responsible for amnesic shellfish poison (Jeffery et al. 2004).

domoic acid
, which can cause Close

Amnesic Shellfish Poison

(ASP, Pseudo-nitzschia) Mainly caused by domoic acid, a toxin produced by some diatoms. When shellfish consume phytoplankton, they can bioconcentrate the toxin leading to a potential health hazard for humans who consume the contaminated shellfish. Hazards may include gastrointestinal symptoms within 24 hours and/or neurologic symptoms within 48 hours of consumption of mussels (Jeffery et al. 2004).

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.

Seasonal Present throughout the summer in medium to low abundances
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).

32 - 36
Temperature -1 - 29 °C


P. pungens: Nitzschia pungens Grunow ex Cleve 1897 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).

P. australis: Nitzschia pseudoseriata G. R. Hasle 1965 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.

(Guiry and Guiry 2012)


Empire Eukaryota
Kingdom Chromista
Subkingdom Harosa
Infrakingdom Heterokonta
Phylum Ochrophyta
Subphylum Khakista
Class Bacillariophyceae
Subclass Bacillariophycidae
Order Bacillariales
Family Bacillariaceae
Genus Pseudo-nitzschia
Species P. pungens (Grunow ex Cleve) G.R. Hasle 1993
Species P. australis Frenguelli 1939

(Guiry and Guiry 2012)


Photosynthetic. Reproduces sexually and asexually.


Cells are wider than 3 μm. Cells form chains by overlapping the ends of adjacent cells. The cells overlap roughly ¼ to ⅓ of the cell length (Horner 2002). The outline of the valve is symmetrical in the Close


(axis, spine) The region of the apex or point. Refers to the most anterior point or region of the cell (HPP 2003).

axis. Central larger interspace is absent (visible only in EM; Hasle and Syvertsen 1997).
*If Close


(scanning electron microscope) A microscope which applies "a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens" (NSF 2011).

is not available, identify these wider (> 3 μm) species as "P. seriata complex".


Length (apical axis): 68 - 144 μm
Width Close

Transapical axis

In diatoms, the longitudinal axis of the valve.

(transapical axis
): 3 - 8 μm


(referring to pores in diatoms) In diatoms, a striation or row of pores on the valve face. "In centric diatoms, striae may be radial, running from the centre of the valve to the margin ... In pennate diatoms, striae may be parallel to the median line of the valve or raphe" (Horner 2002).

: 9 - 18 in 10 μm
Fibulae: 9 - 18 in 10 μm
(Hasle and Syvertsen 1997)

Similar species

See genus description.

Harmful effects

Capable of producing domoic acid, a neurotoxin that causes ASP (amnesic shellfish poisoning; Hasle and Syvertsen 1997). The level of toxicity may be correlated with the amount of urea present, such as that from runoff (Howard et al. 2007).


Neritic (Hasle and Syvertsen 1997).


Cosmopolitan (Hasle and Syvertsen 1997).
Often forms blooms during the summer in Scottish waters (Fehling 2004).
Present throughout the summer in medium to low abundances.

Growth conditions

Information not available.

Environmental Ranges

Depth range (m): 0 - 170
Temperature range (°C): -1.186 - 29.365
Nitrate (μmol L-1): 0.056 - 8.291
Salinity: 31.845 - 36.252
Oxygen (mL L-1): 4.524 - 8.441
Phosphate (μmol L-1): 0.046 - 0.870

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): 0.754 - 16.912
(OBIS 2012, cited in EOL 2012)

Bloom characteristics

Infrequent in local waters. Blooms normally observed off the west coast of Vancouver Island to California.


Encyclopedia of Life (EOL). 2012. Pseudo-nitzschia. Accessed 17 Mar 2012.

Fehling, J. 2004. Diversity, ecology and domoic acid production of Pseudo-nitzschia spp. in Scottish waters. Ph.D. Dissertation. Open University, UK. 309.

Guiry, M. D. and Guiry, G. M. 2012. Pseudo-nitzschia H. Peragallo in H. & M. Peragallo, 1900: 263, 298. Accessed 17 Mar 2012.

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.

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

Howard, M. D. A., Cochlan, W. P., Ladizinsky, N. and Kudela, R. M. 2007. Nitrogenous preference of toxigenic Pseudo-nitzschia australis (Bacillariophyceae) from field and laboratory experiments. Harmful Algae. 6: 206-217.

Ocean Biogeographic Information System (OBIS). 2012. Pseudo-nitzschia. Accessed 17 Mar 2012.

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