Dinophysis fortii

General Dinoflagellate
Shape Clamshell shaped
Size Length 62 - 66 μm, width 41 - 58 μm
Colour Reddish-brown
Connection None (solitary)
Covering Cellulose Close


(plural: thecae) Cell wall. In dinoflagellates, it is composed of cellulose plates within vesicles (Horner 2002).



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

Two Close

Transverse flagellum

In dinoflagellates, one of the two flagella they possess; responsible for the rotation of the cell around its length axis. The two flagella are directed parallel to one another and together, the rotational components result in a helical swimming path (Fenchel 2001).

and Close

Trailing flagellum

In dinoflagellates, one of two flagella they possess; responsible for the movement of the cell and due to its asymmetric arrangement it also causes a rotation of the cell around an axis perpendicular to the longitudinal axis. (Fenchel 2001).



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

Many large centrally placed chloroplasts
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.

. 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.

Most abundant in early summer
Harmful effects Diarrhetic shellfish poisoning Close

Diarrhetic Shellfish Poisoning

(DSP) Mainly caused by okadaic acid, a toxin produced by some diatoms. When shellfish consume phytoplankton, they can bioconcentrate the toxin leading to non-life threatening symptoms that may include diarrhea, nausea, vomiting and cramps (Yasumoto et al. 1985).

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).

and oceanic
Geographic Cold temperate to tropical waters worldwide
Seasonal Early spring to summer
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).

∼34 (optimal)
Temperature ∼13 °C (optimal)


Dinophysis intermedia Pavillard, 1916
Dinophysis laevis (Bergh 1881) Pouchet 1883
Dinophysis ovum Schutt 1895 sensu Martin 1929
(Moestrup and Brandt 2011)


Empire Eukaryota
Kingdom Protozoa
Subkingdom Biciliata
Infrakingdom Alveolata
Phylum Dinoflagellata
Class Dinophyceae
Order Dinophysiales
Family Dinophyciaceae
Genus Dinophysis
Species D. fortii Pavilliard 1923

(Guiry and Guiry 2011)


Dinophysis fortii is a photosynthetic dinoflagellate. It reproduces asexually by Close

Binary fission

A form of asexual reproduction where one cell divides into two identical cells. All prokaryotes and some eukaryotes reproduce in this manner. Compare with mitosis, where the nucleus must also divide, adding an extra step to the process.

binary fission
(Montagnes 2006, Smithsonian 2012).


Cells are broadly Close


Oval or egg-shaped.

and widest Close


The back end of a cell. Opposite of anterior.

. Cells have a curved Close


Relating to the back portion of the cell; opposite to the ventral side.



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

and an almost straight Close


Relating to the underside of an organism; abdominal.

margin. The cell surface has deep Close


A simple hole through the surface of a diatom valve (Smithsonian 2011).

(Tomas 1896). Cells also have two well-developed Close

Sulcal list

(left and right) In dinokont dinoflagellates, a well-defined groove on the ventral surface that is supported by ribs.

sulcal lists
. The left sulcal list is about ⅘ of the cell length. The right sulcal list is also long and can extend beyond the second Close


Features that provide support to other structures in the cell.

(Horner 2002). Dinophysis fortii has a wide rounded posterior and Close


Resembling a net or having a pattern that resembles a net.

on the sulcal lists. D. fortii cells have many large centrally placed chloroplasts (Smithsonian 2012).


Length: 62 - 66 μm
Width: 41 - 58 μm

Similar species

Dinophysis acuta and Dinophysis acuminata. For D. acuta, the two lower sides of the Close


In thecate dinoflagellates, the posterior part of a dinokont cell above the cingulum. The equivalent of a hypocone for naked dinoflagellates.

have an almost straight edge, meaning that they meet at acute angle and form a fairly sharp tip. The hypotheca of Dinophysis acuminata has round or oval-shaped sides, unlike the straight sides of Dinophysis acuta. Both D. fortii and D. acuminata have round or oval-shaped hypothecas, but D. fortii has a bulging side.

Harmful effects

Cells produce Close


Having the ability to combine with or dissolve lipids.

toxins (okadaic acid derivatives and pectenotoxins) causing diarrhetic shellfish poisoning (DSP; Hoshial et al. 2003). D. fortii may be toxic because it eats toxic Close


Phytoplankton within the size range of 0.2 to 2 μm which may be autotrophic, heterotrophic or mixotrophic. They are often found in oligotrophic regions because of their high surface-area-to-volume ratio that better enables them to make use of limited nutrients available (Callieri and Stockner 2002).

species, but not because it produces the toxins itself (EOL 2011). This species was the first species to have been associated with DSP. Cell concentrations as low as 200 cells L-1 can harm humans (Smithsonian 2012).


Neritic and oceanic. D.fortii is believed to be a typical oceanic species. In Japan, it is only brought in to coastal waters by the warm Tsushima current in early spring and summer. This is supported by D. fortii's presence in cooler, saltier oceanic water. D. acuminata, on the other hand, appears in the warmer, medium salinity waters that are characteristic of coastal areas (Hoshial et al. 2003).


Cold temperate to tropical waters worldwide (Steidinger and Tangen 1997).

Growth conditions

Grows well at low temperatures and high salinity (S = 34) oceanic waters (Hoshial et al. 2003). It has also been reported to tolerate lower salinities (Smithsonian 2012).

Environmental Ranges

Depth range (m): 0 - 305
Temperature range (°C): 6.776 - 28.275
Nitrate (μmol L-1): 0.179 - 9.600
Salinity: 31.144 - 39.081
Oxygen (mL L-1): 4.512 - 7.455
Phosphate (μmol L-1): 0.090 - 1.452

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 - 19.032
(EOL 2011)

Bloom characteristics

Highest cell densities (100 cells L-1) are observed at an average temperature of 13.2 °C and at salinities of 33.59 (Hoshial et al. 2003). It is most abundant in early summer (Smithsonian 2012).


Encyclopedia of Life (EOL). 2011. Dinophysis fortii Pavillard. http://www.eol.org. Accessed 09 Sept 2011.

Guiry, M. D. and Guiry, G. M. 2011. Dinophysis fortii Pavillard. http://www.algaebase.org pages 782802. Accessed on 18 July 2011.

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

Hoshial, G., Suzuki, T., Kamiyama, T., Yamasaki, M. and Ichimi, K. 2003. Water temperature and salinity during the occurrence of Dinophysis fortii and Dinophysis acuminata in Kesennuma Bay, northern Japan. Fisheries Science. 69: 1303-1305.

Montagnes, D. 2006. Guide to Harmful Phytoplankton. University of Liverpool. UK. http://www.liv.ac.uk/hab/Data%20sheets/d_fort.htm. Accessed 16 Jan 2012.

Smithsonian Institution 2012. Dinophysis fortii Pavillard 1923. http://botany.si.edu/references/dinoflag/Taxa/Dfortii.htm. Accessed 17 Jan 2012.

Steidinger, K. A. and Tangen, K. 1997. Dinoflagellates. In: Tomas, C. R. (ed.). Identifying Marine Phytoplankton. Academic Press, Inc., San Diego. 531.

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