Heterocapsa triquetra

General Dinoflagellate
Shape Two cones joined at their wider ends, with a protrusion on Close


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

Size Length 16 - 30 μm, width 9 - 18 μm
Colour Golden
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.



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

Many golden chloroplasts present
Lifestyle Close


An organism that is both autotrophic (photosynthesizes or chemosynthesizes) and heterotrophic. That is, it can gain energy both from light (or chemical) energy and also by consuming other organisms. This allows such organisms to take advantage of different environmental conditions.

. 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.

Harmful effects Not 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).

, Close


Of or relating to estuaries.

Geographic Close


Widely distributed; occurring in many parts in the world.

in coastal temperate and low salinity waters
Seasonal 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).

6 - 7
Temperature 10 - 20 °C


Glenodinium triquetrum Ehrenberg 1840
Properidinium heterocapsa (Stein) Meunier 1919
Peridinium triquetra (Ehrenberg) Lebour 1925
Peridinium triquetrum Schiller 1937
(Guiry and Guiry 2011)


Empire Eukaryota
Kingdom Protozoa
Subkingdom Biciliata
Infrakingdom Alveolata
Phylum Dinoflagellata
Class Dinophyceae
Order Peridiniales
Family Heterocapsaceae
Genus Heterocapsa
Species Heterocapsa triquetra (Ehrenberg) Stein 1883

(Guiry and Guiry 2011)


Mixotrophic. It reproduces both sexually and asexually (Guiry 2011).


Cells are 16 - 30 μm long and 9 - 18 μm wide. The Close


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

is conical with straight sides and a rounded end. The hypotheca has an asymmetrical Close


The apical or antapical extensions found in some armoured dinoflagellates; they contain cytoplasm, are covered in thecal plates and can be hollow or partially solid (Horner 2002).

and a unique protrusion. Cells do not have Close


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

. The cells also have a slightly displaced and descending Close


(dinoflagellates) "In dinokont dinoflagellates, a furrow encircling the cell one or many times" (Horner 2002). It is also known as the girdle or transverse groove and may be located at, above, or below the midpoint of the cell with the left and right ends meeting or displaced form one another (Horner 2002). In diatoms, this term describes the collective elements of a diatom girdle: "The cingulum is made up of delicate silica bands that join the two valves of a frustule. Most diatoms possess a cingulum, although some may not" (Spaulding et al. 2010).

. It has numerous golden chloroplast (Horner 2002).


Length: 16 - 30 μm
Width: 9 - 18 μm
(Horner 2002)

Similar species


Harmful effects

None known. H. triquetra is non-toxic and is considered to be a high quality food for Close


An organism that cannot convert inorganic carbon into a usable energy source. Instead, it consumes other organisms to obtain organic carbon for growth.

dinoflagellates, ciliates and copepods (Olli 2004). At cell densities above 5000 cells L-1, blooms may cause water Close


Change of water colour due to an algal bloom.

to orange-brown (Olli 2004).


Neritic and estuarine. Low salinity water worldwide (Steidinger and Tangen 1997).


Found in coastal and estuarine waters.

Environmental Ranges

Depth range (m): 0 - 270
Temperature range (°C): -1.813 - 23.128
Nitrate (μmol L-1): 0.584 - 9.364
Salinity: 19.590 - 37.775
Oxygen (mL L-1): 4.981 - 9.002
Phosphate (μmol L-1): 0.051 - 1.129

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): 0.687 - 29.549

Bloom characteristics

H. triquetra causes extensive blooms in low salinity temperate coastal waters during the summer at temperatures between 10 °C and 20 °C. Blooms disappear in late August or early September (Olli 2004). Coastal blooms are often caused by Close


Water that is enriched in natural or artificial mineral and organic matter, which promotes an abundance of plant life (i.e., algae), and can result in reduced oxygen conditions.

and local artificial mixing caused by large passenger ferries (Olli 2004). Large July and August blooms have been observed in the Baltic Sea near Finland for these reasons (Lindholm and Nummelin 1999). Often, the bulk of the population lives in the upper surface layer, in light levels above 100 μE m-2 s-1 (Olli 2004).


Encyclopedia of Life (EOL). Heterocapsa triquetra (Ehrenberg) Stein, 1883. http://www.eol.org/pages/10237. Accessed 26 Aug 2011.

Guiry, M. D. and Guiry, G. M. 2011. Heterocapsa triquetra (Ehrenberg) Stein 1883 http://www.algaebase.org/search/species/detail/?species_id=45678. Accessed 22 Aug 2011.

Guiry, M. D. 2011. Heterocapsa triquetra (Ehrenberg) Stein 1883 http://www.marinespecies.org/aphia.php?p=taxdetails&id=110153. Accessed 21 Oct 2011.

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

Lindholm, T. and Nummelin, C. 1999. Red tide of the dinoflagellate Heterocapsa triquetra (Dinophyta) in a ferry-mixed coastal inlet. Hydrobiologia. 393: 245-251.

Olli, K. 2004. Temporary Cyst Formation of Heterocapsa triquetra (Dinophyceae) in Natural Populations. Marine Biology. 145: 1-8.

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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