Trade with organic products, especially with meat is in Czech Republic very poor.  I hope for the better supply and I decided to add my piece of interest to the organic market to support it.

Knowledge of  correct description of diatom is priceless in the diatom species identification because you must know what morphological features search for when observing diatoms under microscopy as well as searching in diatom identification atlases. Although the knowledge is crucial I did not find any systematic and understandable instruction of the basic terms. In the following text I will try to offer mine findings demonstrated on the figure below the text.

Basically, the structure of each diatom cell is that of a box. The lid and bottom of the box are the valves, and the sides are formed by the girdle or connecting bands which overlap slightly, one half of the cell being larger than the other. The overlapping connecting bands are known as the girdle. This box-like cell differs from all other algal cells in being encased by a skeleton of silica which is often modified to form intricate shapes and is transversed by numerous canals and pores which connect the inner protoplasmic contents with the external aqueous environment.

Frustule terms:

• Valves — parts of frustule corresponding with the top and bottom of a box
• Valve Mantle — part of valve bent over at the sides
• Epivalve or Epitheca — older, larger, upper valve
• Hypovalve or Hypotheca— younger, smaller, lower valve
• Girdle (cingulum) or connecting bands (copulae)— two-ended, overlapping side faces of frustule joined to edges of valves— corresponding with the sides of a box
• Intercalary bands — incomplete ring-like or scale-like bands between valve and girdle, as in Rhizoselenia sp.
• Pervalvar (cell) axis — imaginary line joining the two valve centres
• Apical axis — longer axis of valve
• Transapical axis — shorter axis of valve
• Collar (collum) — distal part of valve mante without any structure typical for Aulacoseira sp.

Terms describing features within a valve:

• Nodules — small internal rounded or conical thickenings in pennate diatoms
• Raphe — a slit through the valve joining two nodules
• Striae — row of dots, areol, or alveol
• Interstriae - line between the rows of areol on the head, or band of the valve
• Lineations — fine linear perforation extending across the width of the striae
• Pseudoraphe — a clear longitudinal space separating two vertical rows of transverse markings.
• Keel— a wing-like expansion of valve, containing raphe — in Nitzschia and Surirella sp.
• Pores — perforations in the walls
• Spinulae — small spines formed from marginal pores, as in Thalassiosira sp.
• Areolae — cavities closed by a thin siliceous membrane and separated by partitions
• Anulus — hyaline ring in the valve center, often it is closing several areols, often in Cyclotella sp., Cyclostephanos sp., and Stephanodiscus sp.
• Alveoli — elongated and partially enclosed chambers extending from the axial or central area to the periphery, as in Pinnularia sp.
• Costate — strong ribs, closed outside and open inside (coarse striae)
• Punctae — linear series of tiny dots resembling striations or striae
• Setae — long delicate spines at corners of Chaetoceros sp.and other cells
• Septa — ingrowths from intercalary bands, as in Grammatophora sp.
• Carinoportulae – special short tubercles at the center of the valve, probably serving as connecting elements for Orthoseira roseana and related species

Spore types :

• Auxospore — thin-walled spore, sometimes sexual in nature, larger than parent cell or cells
• Microspore — small flagellated spore
• Resting spore — medium, thick-walled spore

For the more detailed description of diatom frustule, e.g. description of different stiae and areolae patterns; I can recommend Barber, H.G, and Hawort, E.Y., 1994. A guide to terminology of the diatom frustule, with a Key to the British Freshwater Genera. Freshwater Biological Assn., 112 pp.

Other used sources for the description:

Houk,V., Freshwater centric diatoms (in czech Sladkovodní centrické rozsivky) - PowerPoint presentation, Institute of Botany AV ČR, Třeboň

Cassie, V., 1959. Marine plankton diatoms. Journal of the Biological Society 7 (3), p. 108-119.

Any comments, additions and corrections from the experts are welcome!

Although there are not many of diatom specialist in Czech Republic, following information is exclusively for them I could not resist to publish it English translation of old (currently not used) names of diatom genus  is not reasonable. So I will leave English speaking readers with the question Do exist (or are used) Your national terms instead of Latin names of diatoms?

Happy new year 2009!

Welcome on my pages where You will find by the end of this year many useful and interesting information from various fields. Starting with my scientific focus to diatom analysis implications in paleoclimatology and ending with my personal life. Enjoy and if You have any comments, please use the comments windows.

Anna Píšková