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Dinophysis acuta

Classification
General Dinoflagellate
Description
Shape Clamshell shaped
Size Length 54 - 94 μm, diameter 43 - 60 μm
Colour Reddish-orange
Connection None (solitary)
Covering Cellulose Close

Theca (plural: thecae)

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

theca
Close

Flagellum (plural: flagella)

A tail-like projection that sticks out from the cell body and enables movement.

Flagella		 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).

(transverse 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).

trailing)
Close

Chloroplast

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

Chloroplast		 Many red-brown chloroplasts
Behaviour
Lifestyle Close

Photosynthesis

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.

Photosynthetic. Asexual 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).
Close

Bloom

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.

Bloom		 Hot summer preceded by dry winters and strong spring Close

Upwelling

A wind-driven mechanism of mixing the water column. Cold, dense, nutrient-rich, and often oxygen-poor water from depths rises to replace the warmer nutrient-poor surface water. This input of nutrients can have a significantly increase primary productivity in a region (Dugdale 1985).

upwelling
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).

(DSP)
Distribution
Habitat Close

Neritic

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).

Neritic and oceanic
Geographic Cold temperate waters worldwide
Seasonal Spring to summer
Growth Conditions
Salinity Haline Close

Stratification

The development of distinct non-mixing layers in the water column resulting from a steep gradient in density, which is caused by differences in temperature and/or salinity.

stratified waters
Temperature Thermally stratified waters

Synonym(s)

Classification

Empire Eukaryota
Kingdom Protozoa
Subkingdom Biciliata
Infrakingdom Alveolata
Phylum Dinoflagellata
Subphylum
Class Dinophyceae
Subclass
Order Dinophysiales
Family Dinophyciaceae
Genus Dinophysis
Species D. acuta Ehrenberg 1839

(Guiry and Guiry 2011)

Lifestyle

Photosynthetic. Reproduces asexually by binary fission.

Description

Clamshell shaped, with a crown on top, a wing or fin at the side and a pointed Close

Posterior

The back end of a cell. Opposite of anterior.

posterior (Dodge 1982, Horner 2002). Cells are Close

Lateral

Relating to a side-to-side direction.

laterally flattened with posterior forming blunt Close

Ventral

Relating to the underside of an organism; abdominal.

ventrally directed projection. Cells' broadest width is below the midpoint of the Close

Hypotheca

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

hypotheca. Cells have three 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, with left Close

Sulcus

"In dinokont dinoflagellates, the longitudinal area on the ventral surface that forms a furrow or depression and houses the longitudinal (trailing) flagellum" (Horner 2002).

sulcus widening towards posterior end. The first Close

Ribs

Features that provide support to other structures in the cell.

rib points towards the Close

Anterior

The front. The part of the cell in the direction of movement. Opposite of posterior (HPP 2003).

anterior of the cell. The second rib is ventral. The third rib is pointing to the posterior of the cell. Two-thirds of the hypotheca (anterior side) has gentle convex sides, with straight Close

Dorsal

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

dorsal edge in the posterior third (Dodge 1982). The side of the hypotheca from the third rib is straight while the opposite side is round forming acute angle at the junction. Chloroplasts are reddish-brown (Dodge 1982).

Measurements

Length: 54 - 94 μm
Diameter: 43 - 60 μm
(Kraberg et al. 2010)

Similar species

This species can easily be confused with Dinophysis norvegica. D. acuta can be differentiated by its larger size and has its widest section below the mid-section of the cell (below two-thirds of the cell length), while D. norvegica is wide in the middle (Smithsonian 2011). The two posterior sides of the hypotheca have an almost straight edge hence, meet at acute angle forming a fairly sharp tip.

Harmful effects

Produces Close

Lipophilic

Having the ability to combine with or dissolve lipids.

lipophilic toxins (okadaic acid derivatives and pectenotoxins) that cause diarrhetic shellfish poisoning (DSP; Escalera et al. 2010).

Habitat

Neritic and oceanic (Horner 2002).

Distribution

Found worldwide in cold temperate waters (Horner 2002).

Growth conditions

There has been little evidence of blooms being associated with elevated Close

Nutrients

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.

nutrients concentrations (Miota et al. 2006). Very high abundances are found in subsurface layers of thermally and saline-stratified Close

Water column

Referring to a water system from the surface to the bottom sediments. This can be used to understand processes of stratification, mixing and their relationship to nutrient transport. Temperature, salinity, pH, and nutrient levels often vary along the length of the water column.

water columns (Miota et al. 2006).

Environmental Ranges

Depth range (m): 0 - 175
Temperature range (°C): -1.314 - 22.429
Nitrate (μmol L-1): 0.551 - 10.777
Salinity: 18.564 - 36.252
Oxygen (mL L-1): 4.915 - 9.116
Phosphate (μmol L-1): 0.048 - 0.745
Close

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).

Silicate (μmol L-1): 0.754 - 36.110
(EOL 2011)

Bloom characteristics

Summer blooms start in early July. Blooms reach a maximum in late August. Sporadic smaller spring blooms can also be seen. Larger blooms are often seen in warm summers that were preceded by dry winters and lower upwelling in the spring (Regeura et al. 1995, Miota et al. 2006).

References

Dodge J. D. Marine Dinoflagellates of British Isles. Her Majesty's Stationary Office, London, UK. 303.

Encylopedia of Life (EOL). 2011. Dinophysis acuta Ehrenberg 1839. http://eol.org/pages/901406/details. Accessed 26 Dec 2011.

Escalera, L., Reguera, B., Miota, T., Pazos, Y. and Cerejo, M. 2010. Bloom dynamics of Dinophysis acuta in an upwelling system: in situ growth versus transport. Harmful Algae. 9(3): 312-322.

Guiry, M. D. and Guiry, G. M. 2011. Dinophysis acuta Ehrenberg 1839. http://www.algaebase.org/search/species/detail/?species_id=52218. Accessed 05 May 2011.

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

Miota, M. T., Gonçalves, L. S., Oliveira, P. B. and Falcão, M. 2006. A bloom of Dinophysis acuta in a thin layer off north-west Portugal. African Journal of Marine Science. 28(2): 265-269.

Reguera, B., Bravo, I. and Fraga, S. 1995. Autoecology and some life history stages of Dinophysis acuta Ehrenberg. Journal of Planktonic Research. 17(5): 999-1015.

Smithsonian Institution. 2011. Dinophysis acuta Ehrenberg 1839. http://botany.si.edu/references/dinoflag/Taxa/Dacuta.htm. Accessed 23 Oct 2011.

Steidinger, K. A. and Tangen, K. 1997. Dinoflagellates. In: Tomas, C. R. (ed.) Identifying Marine Phytoplankton. Academic Press, Inc., San Diego. 429.