Diatom facts for kids

Quick facts for kids Diatoms
Marine diatoms
Scientific classification
Domain:	Eukaryota
Kingdom:	Chromalveolata
Phylum:	Heterokontophyta
Class:	Bacillariophyceae

Diatoms (Greek: dia = through + temnein = to cut: "cut through") are a big group of eukaryotic algae. They are one of the most common types of phytoplankton. Most diatoms are unicellular, although some form chains or simple colonies. Diatom cells are encased within a unique cell wall made of silica (SiO₂). These walls, called frustules, take many forms, some quite beautiful and ornate. They usually consist of two asymmetrical sides with a split between them, which gives the group its name.

Diatom chloroplasts were probably derived from those of red algae. The fossil record of diatoms starts in strata of the Lower Jurassic, ~185 million years ago. Molecular clock evidence suggests an earlier date for their origin. The entire genomes of two species of diatom have been analysed. The analysis reveals that hundreds of genes in both species came from bacteria.

Diatoms have some practical uses. Diatom communities are a popular tool for monitoring environmental conditions, past and present. They are commonly used in studies of water quality. They are also of interest to nanotechnology.

Images for kids

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  Selections from Ernst Haeckel's 1904 Kunstformen der Natur (Art Forms of Nature), showing pennate (left) and centric (right) frustules.

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  Shape classification of diatom frustules. The images are 3D models. The actual sizes of the frustules are about 10–80 μm.
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  Structure of a centric diatom frustule
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  Planktonic diatoms such as Thalassiosira sp. (56-62), Asteromphalus sp. (63), Aulacoseira sp. (64-66), and Chaetoceros (see twin image above) often grow in chains, and have features such as spines which slow sinking rates by increasing drag.

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  Some Thalassiosira diatoms form chain-like colonies, like these collected near the Antarctic peninsula coast by the schooner of the Tara Oceans Expedition for plankton research. This projection of a stack of confocal images shows the diatoms' cell wall (cyan), chloroplasts (red), DNA (blue), membranes and organelles (green).

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  Regions of high abundance of diatoms in the ocean
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  Pennate diatom from an Arctic meltpond, infected with two chytrid-like [zoo-]sporangium fungal pathogens (in false-colour red). Scale bar = 10 μm.

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  Light microscopy of a living diatom.  Numbered graduations are 10 micrometres apart

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  Light microscopy of several species of living freshwater diatoms
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  Centric diatom
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  Linked diatoms
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  Thalassiosirales Stephanodiscus hantzschii
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  Coscinodiscophyceae Isthmia nervosaIsthmia nervosa
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  Coscinodiscophyceae Odontella aurita
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  Intricate silicate (glass) shell, 32-40 million years old, of a diatom microfossil
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  Diatomaceous earth as viewed under bright field illumination on a light microscope. This image consists of a mixture of centric (radially symmetric) and pennate (bilaterally symmetric) diatoms suspended in water. The scale is 6.236 pixels/μm, the image is 1.13 by 0.69 mm.

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  Diatom Surirella spiralis

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  Diatoms Thalassiosira sp. on a membrane filter, pore size 0.4 μm.

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  Stand-alone cell of Bacillaria paxillifer

See also

In Spanish: Diatomea para niños