Pseudo-nitzschia delicatissima

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, boat-shaped
Size Length 40 - 76 μm, width ∼2 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.

Information not available
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 Found mainly in the summer in local and European waters
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).

24 - 38
Temperature -2 - 29 °C


Nitzschia actydrophila 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.

Nitzschia delicatissima 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).

(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. delicatissima (Cleve) Heiden 1928

(Guiry and Guiry 2012)


Photosynthetic. Reproduces sexually and asexually.


Cells are narrower than 3 μm. Cells form chains by overlapping the cell ends. The cells overlap roughly 19 of the cell length. Cells may be slightly Close



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. A large central interspace is present (area devoid of pores 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 narrower (< 3 μm) species as "P. delicatissima complex."


Length Close


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

axis): 40 - 76 μm
Width Close

Transapical axis

In diatoms, the longitudinal axis of the valve.

(transapical axis
): ∼2 μm
Height Close

Pervalvar axis

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

(pervalvar axis
): 1.5 - 2 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).

: 36 - 40 in 10 μm
Fibulae: 19 - 25 in 10 μm
(Hasle and Syvertsen 1997, Kraberg et al. 2010)

Similar species

See genus description.

Harmful effects

Capable of producing domoic acid, a neurotoxin that causes ASP (amnesic shellfish poisoning; Hasle and Syvertsen 1997).


Neritic (Hasle and Syvertsen 1997) and oceanic (Kraberg et al. 2010).


Cosmopolitan (Hasle and Syvertsen 1997).
Found mainly in the summer, sometimes in high abundances, around Northern European seas (Kraberg et al. 2010). Blooms in early spring and fall on the Mediterranean coast (Ribera d'Alcalà et al. 2004). Forms non-toxic blooms in spring in Scottish waters (Fehling 2004).
Present throughout the summer. Sometimes found in high numbers in conjunction with colonies of Chaetoceros socialis.

Growth conditions

May be able to grow under a wide range of conditions due to high genetic diversity (Orsini et al. 2004). May prefer shorter Close


The amount of time in a day that an organism is exposed to daylight. This varies between seasons, with photoperiods being longer in the summer and shorter in the winter.

, such as those during the spring (Fehling et al. 2005). May be favoured by high concentrations of dissolved organic matter, such as after blooms of other species (Loureiro et al. 2009). More readily uses ammonium than urea as a source of nitrogen, but may use urea under low nitrogen conditions (Loureiro et al. 2009).

Environmental Ranges

Depth range (m): 0 - 2000
Temperature range (°C): -2.045 - 29.468
Nitrate (μmol L-1): 0.030 - 28.280
Salinity: 24.378 - 37.775
Oxygen (mL L-1): 3.756 - 9.116
Phosphate (μmol L-1): 0.046 - 2.337

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 - 59.039
(OBIS 2012, cited in EOL 2012)

Bloom characteristics

Information not available.


Encyclopedia of Life (EOL). 2012. Pseudo-nitzschia delicatissima. 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.

Fehling, J., Davidson, K. and Bates, S. S. 2005. Growth dynamics of non-toxic Pseudo-nitzschia delicatissima and toxic P. seriata (Bacillariophyceae) under simulated spring and summer photoperiods. Harmful Algae. 4: 763-769.

Guiry, M. D. and Guiry, G. M. 2012. Pseudo-nitzschia delicatissima (Cleve) Heiden. 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.

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

Loureiro, S., Jauzein, C., Garcés, E., Collos, Y., Camp, J. and Vaqué, D. 2009. The significance of organic nutrients in the nutrition of Pseudo-nitzschia delicatissima (Bacillariophyceae). Journal of Plankton Research. 31(4): 399-410.

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

Orsini, L., Procaccini, G., Sarno, D. and Montresor, M. 2004. Multiple rDNA ITS-types within the diatom Pseudo-nitzschia delicatissima (Bacillariophyceae) and their relative abundances across a spring bloom in the Gulf of Naples. Marine Ecology Progress Series. 271: 87-98.

Ribera d'Alcalà, M., Conversano, F., Corato, F., Licandro, P., Mangoni, O., Marino, D., Mazzocchi, M. G., Modigh, M., Montresor, M., Nardella, M., Saggiomo, V., Sarno, D. and Zingone, A. 2004. Seasonal patterns in plankton communities in a pluriannual time series at a coastal Mediterranean site (Gulf of Naples): an attempt to discern recurrences and trends. Scientia Marina. 68(Suppl. 1): 65-83.

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