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Dictyocha speculum

Classification
General Silicoflagellate
Description
Shape Spherical
Size Length 19 - 35 μm (excluding Close

Spine

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

spines)
Colour Yellow-brown
Connection None, solitary
Covering No covering, but with hexagonal silica skeleton
Close

Flagellum

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

Flagella		 One, Close

Anterior

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

anterior
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		 Numerous
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. Sexual/asexual.
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		 Information not available
Harmful effects Physical obstruction of fish gills
Distribution
Habitat Coastal and oceanic
Geographic Close

Cosmopolitan

Widely distributed; occurring in many parts in the world.

Cosmopolitan in cold and temperate waters
Seasonal Spring around Vancouver Island
Growth Conditions
Close

Salinity

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).

Salinity		 15 - 25 (optimal)
Temperature 11 - 15 °C (optimal)

Synonym(s)

Distephanus speculum (Ehrenberg) Haeckel 1887
Cannopilus calyptra Haeckel 1887 Close

Heterotypic

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.

(heterotypic)
(Horner 2002, Guiry and Guiry 2011)

Classification

Empire Eukaryota
Kingdom Chromista
Subkingdom Chromobiota
Infrakingdom Heterokonta
Phylum Heterokontophyta
Subphylum
Class Dictyochophyceae
Subclass
Order Dictyochales
Family Dictyochaceae
Genus Dictyocha
Species D. speculum Ehrenberg 1839

(Guiry and Guiry 2011)

Lifestyle

Photosynthetic. Sexual reproduction by Close

Isogamy

The simplest type of sexual reproduction between gametes that are similar in size and shape. Instead of being classified as male and female cells, organisms of different mating types (i.e., different size and shape of gamete) can fuse to form a zygote (Botany Dictionary 2002).

isogamy; asexual reproduction by Close

Aplanospore

A thin-walled spore that relies on water currents for passive transport. It is produced by some phytoplankton (including Scenedesmus and Geminella species [phylum Chlorophyta]) as a means of asexual reproduction. Upon germination, it develops a new cell wall distinct from the parent cell. The production of aplanospores may be a hereditary feature or may be an adaptation to withstand unfavourable environmental conditions (Transeau 1916).

aplanospores and Close

Statospore

An internally formed spore in its resting stage. A thick-walled, resistant spore formed within the frustules of various centric diatoms.

statospores (Guiry 2011). Skeletal, Close

Naked

(athecate, unarmoured dinoflagellates) Without a theca. Referring to "cells without a cell wall" (Horner 2002). The opposite of thecate or armoured.

naked, Close

Multinucleate

Describing an organism containing multiple nuclei. This occurs after a cell division in which the cytoplasm was not divided to form separate daughter cells.

multinucleate, and Close

Amoeboid

(shape) Exhibiting a jelly-like changeable form.

amoeboid stages have been recorded (Horner 2002).

Description

Cells are solitary, roughly spherical and slightly flattened with one anterior flagellum. The external silica skeleton is composed of tubular elements and consists of two hexagonal rings, with six spines radiating from the corners of the large ring. Six bars connect the corners of the inner ring with the sides of the outer ring. Chloroplasts are golden-brown and Close

Discoid

Disc-shaped.

discoid (Horner 2002). The Close

Nucleus

(plural: nuclei) In eukaryotic cells, a membrane-bound organelle that contains the cell's genetic information; the nucleus controls the activities of the cell by controlling gene expression.

nucleus is located in the centre of the cell (Kraberg et al. 2010).
Cell contents are held inside the skeleton by six small protruding spines on the sides of the large ring. Close

Pseudopodium/pseudopodia

A semi-permanent extension of the cytoplasm used for locomotion and feeding by some flagellate protozoans.

Pseudopodia extend from the cell surface (Horner 2002). Flagellum is as long as the cell or slightly shorter (Kraberg et al. 2010).
The naked stage has a granular appearance due to chloroplasts (Haigh 2010). Cells with 5 - 9 spines have also been recorded (Henriksen et al. 1991).

Measurements

Length (skeletal form): 19 - 35 μm, ∼65 μm with spines
Length (multinucleate stage): up to 500 μm
(Moestrup and Thomsen 1990, Haigh 2010, Kraberg et al. 2010)

Similar species

Dictyocha fibula, which has four protruding spines and four "windows" (Throndsen 1997), instead of the six spines on D. speculum.

Harmful effects

May produce toxins, and may also cause mechanical irritation at high concentrations. It is recommended to be alert for negative effects at concentrations > 100 cells mL-1 of any form. Skeletal forms in concentrations of ∼400 cells mL to 1000 cells mL-1 have been recorded to kill fish. Harmful concentrations of the naked form are ∼500 cells mL-1 (Haigh 2010).
The skeletal stage has killed trout in France. The skeletons irritate the gills, causing them to produce mucus, and eventually causing asphyxiation (Horner 2002). Fish kills in Denmark during a bloom were likely caused by Close

Anoxic

Describing a condition where there is no available oxygen for primary production. Oxygen may be present in complexed forms that are not available for phytoplankton. A related term is hypoxia, where oxygen is present at very low concentrations.

anoxia, as no toxic effects were found for the naked stage (Henriksen et al. 1991).

Habitat

Coastal and oceanic (Throndsen 1997).

Distribution

Geographic:
Cosmopolitan in cold and temperate waters (Throndsen 1997).
Seasonal:
In Northern European seas, it can be found throughout the year, though mainly during late winter and spring (Kraberg et al. 2010). In Danish waters, the skeletal stage is most abundant in the autumn and the naked stage is most abundant in the spring (Moestrup and Thomsen 1990).
Local:
Skeletal form is mainly found during spring around Vancouver Island (Haigh 2010).

Growth conditions

Optimal growth conditions of salinity 15 - 25, within a temperature range of 11 - 15 °C (Henriksen et al. 1991).
Blooms of the skeletal form may be common under high silica conditions, such as in spring or after heavy run-off (Haigh 2010), while blooms of the naked stage may be associated with low silica conditions (Jochem and Babenerd 1989).
May be better adapted to Close

Oligotrophic

Describing an aquatic ecosystem with low nutrient and organic matter accumulation and high dissolved oxygen content.

oligotrophic conditions (low 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, high oxygen) than D. fibula due to higher relative abundances in the summer (Rigual-Hernandez et al. 2010).

Environmental Ranges

Depth range (m): 0 - 292
Temperature range (°C): -1.938 - 12.224
Nitrate (μmol L-1): 0.543 - 31.807
Salinity (PSU): 25.730 - 34.979
Oxygen (mL L-1): 6.371 - 8.728
Phosphate (μmol L-1): 0.048 - 2.190
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): 2.292 - 66.097
(OBIS 2011, cited in EOL 2011)

Bloom characteristics

Information not available.

References

Encyclopedia of Life. (EOL). 2011. Dictyocha speculum Ehrenberg. http://www.eol.org/pages/899617. Accessed 26 Jun 2011.

Guiry, M. D. 2011. Dictyocha speculum Ehrenberg, 1837. World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=157260. Accessed 26 Jun 2011.

Guiry, M. D. and Guiry, G. M. 2011. Dictyocha speculum Ehrenberg. http://www.algaebase.org/search/species/detail/?species_id=54513. Accessed 26 Jun 2011.

Haigh, N. 2010. Harmful Plankton Handbook. Nanaimo, BC, Canada. 52.

Henriksen, P., Knipschildt, F., Moestrup, Ø. and Thomsen, H. A. 1993. Autecology, life history and toxicology of the silicoflagellate Dictyocha speculum (Silicoflagellata, Dictyochophyceae). Phycologia. 32(1): 29-39.

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

Jochem, F. and Babenerd, B. 1989. Naked Dictyocha speculum - a new type of phytoplankton bloom in the Western Baltic. Marine Biology. 103(3): 373-379.

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

Moestrup, Ø. and Thomsen, H. A. 1990. Dictyocha speculum (Silicoflagellata, Dictyocho-phyceae), studies on armoured and unarmoured stages. K. Danske Vidensk. Selsk. Biol. Skr. 37: 1-56.

Ocean Biogeographic Information System (OBIS). 2011. Dictyocha speculum. http://www.iobis.org/mapper/?taxon_id=434073. Accessed 26 Jun 2011.

Rigual-Hernandez, A. S., Barcena, M. A., Sierro, F. J., Flores, J. A., Hernandez-Almeida, I., Sanchez-Vidal, A., Palangues, A. and Heussner, S. 2010. Seasonal to interannual variability and geographic distribution of the silicoflagellate fluxes in the Western Mediterranean. Marine Micropaleontology. 77(1-2): 46-57.

Throndsen, J. 1997. The planktonic marine flagellates. In: Tomas, C. R. (ed.) Identifying marine Phytoplankton. Academic Press, Inc., San Diego. 591-730.