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Genus: Chaetoceros

Classification
General Close

Centric

(diatoms) Having radial symmetry, i.e., cell is shaped like a coin or a tuna can or a soup can.

Centric diatom
Description
Shape Elliptic cylinder
Size Large diameter 2 - 85 μm, length 2 - 45 μm,
Colour Yellow-brown
Connection Crossing/touching of adjacent 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
Covering Silica Close

Frustule

In diatoms, the hard and porous silica cell wall (Horner 2002).

frustule
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Flagellum

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

Flagella		 None
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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		 Variable
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

Resting spore

In diatoms, a cell that requires a dormancy period prior to germination and can survive for several years; usually developed to survive adverse conditions. They are commonly observed in centric but not pennate diatoms. The morphology of the spore may be similar or different from a vegetative cell; they usually have heavily silicified walls and are rich in storage products (Horner 2002).

Resting spores, Close

Auxospore

In diatoms, the special cells that restore normal size following cell division. Auxospores are associated with sexual reproduction (Horner 2002).

auxospores, microspores present in some species
Harmful effects Some species can cause physical damage to gills
Distribution
Habitat Mostly 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, few oceanic
Geographic Close

Cosmopolitan

Widely distributed; occurring in many parts in the world.

Cosmopolitan
Seasonal Common throughout the summer, especially during late spring and early fall
Growth Conditions
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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		 19 - 38
Temperature -2 - 29°C
C. convolutus C. debilis
C. decipiens C. didymus
C. radicans C. similis
C. socialis

Classification

Empire Eukaryota
Kingdom Chromista
Subkingdom Harosa
Infrakingdom Heterokonta
Phylum Ochrophyta
Subphylum Khakista
Class Bacillariophyceae
Subclass Coscinodiscophycidae
Order Chaetocerotales
Family Chaetocerotaceae
Genus Chaetoceros Ehrenberg 1844

(Guiry and Guiry 2012)

Lifestyle

Photosynthetic. Reproduces sexually and asexually (Guiry 2012). Resting spores, auxospores and microspores are present in some species (Cupp 1943).

Description

Cells are usually connected in chains, and are roughly rectangular in Close

Girdle

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).

girdle view and elliptical in Close

Valve

In diatoms, the structurally distinct halves of the cell wall (Becker 1996).

valve view (elliptic cylinder), with two spines arising from each valve. Adjacent cells are linked by the crossing or touching of the spines near the base (Cupp 1943). Cells are yellow-brown in colour (Guiry 2012).

Measurements

Large diameter Close

Apical

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

(apical axis): 2 - 85 μm
Length 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): 2 - 45 μm
(Hasle and Syvertsen 1997, Kraberg et al. 2010)

Key to local species

Spines thick, covered in tiny spines, filled with chloroplasts; cells bullet-shaped. C. convolutus
Spiralling chains; spines thin, directed out from spiral. C. debilis
Valves concave with semi-circular protrusion. C. didymus
Spines thin and covered in tiny spines; chain twisted about its axis. C. radicans
Valves with a raised centre, touching adjacent cell, forming a figure-eight-shaped Close

Aperture

"In some diatoms, the space between the valves of adjacent cells in chains" (Horner 2002).

aperture; spines very straight and extend out diagonally. C. similis
4 to 10 chloroplasts; valves concave with corners touching adjacent cells; adjacent spines usually fused for a short distance before diverging. C. decipiens/lorenzianus
Forms large colonies of multiple short chains; chains of small cells tied to the centre of colony by a bundle of spines. C. socialis

Harmful effects

The species with larger, thicker spines can cause physical damage to organisms' gills when present in large numbers (Kraberg et al. 2010).

Habitat

Mostly neritic, with few which are oceanic (Cupp 1943).

Distribution

Mostly cosmopolitan (Hasle and Syvertsen 1997).

Environmental Ranges

Depth range (m): 0 - 470
Temperature range (°C): -1.952 - 29.468
Nitrate (μmol L-1): 0.053 - 34.037
Salinity: 18.564 - 37.775
Oxygen (mL L-1): 4.139 - 9.192
Phosphate (μmol L-1): 0.046 - 2.358
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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): 0.648 - 92.735
(OBIS 2012, cited in EOL 2012)

References

Cupp, E. E. 1943. Marine Plankton Diatoms of the West Coast of North America. University of California Press. Berkeley, California. 238.

Encyclopedia of Life (EOL). 2012. Chaetoceros. http://eol.org/pages/12010/overview. Accessed 18 Mar 2012.

Guiry, M. D. 2012. Chaetoceros Ehrenberg, 1844. http://www.marinespecies.org/aphia.php?p=taxdetails&id=148985. Accessed 18 Mar 2012.

Guiry, M. D. and Guiry, G. M. 2012. Chaetoceros Ehrenberg, 1844: 198. http://www.algaebase.org/search/genus/detail/?genus_id=43689. Accessed 18 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.

Ocean Biogeographic Information System (OBIS). 2012. Chaetoceros. http://www.iobis.org/mapper/?taxon_id=611649. Accessed 18 Mar 2012.