Diatomscapes: Images

  • Where: Exhibit Gallery, Strozier Library.
  • When:  Nov. 3 - 14, 2008

See Special Collections Hours for times exhibit is open.


What is this about?

Science can also be art! Come look at some of the fascinating images that will be on display at Strozier Library Special Collections from Nov 3 - 14.

Provided to the University Libraries by Dr. Akshinthala K. Prasad and digitized by the Digital Library Center, these images of tiny creatures that "thrive in freshwater, saltwater, brackish water and even semiterrestrial environments" will cause you to think about what other wonders lie "just out of sight."

Also, see the article in the latest research in review on Diatoms.

More information on Diatoms

Silica, the most abundant material in the earth’s crust, is often referred to as amorphous, hydrated, and polymerized silicic acid with unknown molecular weight. Considering the abundance of silica in nature it is remarkable that only a few groups of organisms have utilized this element in their systems. Siliceous structures occur in a variety of organisms but predominate in the more “primitive” forms of life, in which amorphous, hydrated silica forms cell walls, tests, scales and other skeletal features. Of the fourteen divisions of the algae, diatoms are one of the few groups that make any notable use of silicon.

Diatoms are a Johnny-come-lately class of microscopic, single-celled plants that thrive in freshwater, saltwater, brackish water and even semiterrestrial environments, having evolved at about the same time as flowering plants, birds and mammals at the end of the Jurassic period. Diatoms, like birds and mammals, have characteristic mineralized skeletons, generally constituting a considerable proportion of their weight. By contrast to our own internal skeletons, which are phosphotic, those of diatoms are siliceous (referred as “frustules”), being initially composed of amorphous oxalate.

Diatom frustules have aesthetically pleasing, radially or bilaterally symmetrical patterns of pores and grooves, pits and prominences, spines and spinelets, tubes and other processes, many being reminiscent of lace doilies. Their abundance, wide distribution, and their well-preserved, glass-like shells make them ideal tools for a wide range of applications.

Ecologically and geochemically, diatoms are of immense significance, because of the part they play in the silicon and carbon cycles; it has been estimated, for instance, that they may account for 20-25% of global primary production. Fossil diatoms are used as stratigraphic markers for tertiary sediments, both marine and freshwater, not to mention their importance in paleoecological reconstruction, oil exploration, forensic examination, cell biology and biochemistry. Diatoms store oil as reserve food and for floatation.

Over millions of years, they have become a primary source of fossil fuel and these diatoms are used in dating and mapping the distribution of petroleum-bearing strata. Fossil diatom deposits (of age Miocene through Quaternary), freshwater or marine, a.k.a. diatomite or “kieselgur”, has been mined around the world for centuries and they have wide Industrial applications because of their high porosity and low density. Diatomite is a natural adsorbent that is unparalleled and it was known to be a key ingredient in Alfred Noble’s Dynamite explosives for their adsorbent property. Other major industrial uses are isolation and filtration. Because of their high porosity nature, it is often used in isolation and filtration. Many salt-water diatoms can be harmful, especially in a bloom. The results of each bloom have been species-specific, and identification of species remains a high priority. For all these different types of study, accurate identification is essential. Patterns of ornamentation and perforation in the siliceous walls of diatoms not only have long been admired for their symmetry and order but also form the basis for the identification of these single-celled plants. Altogether, there are probably between 105 and 106 species of diatoms, of which, a tenth or less have yet been described, almost exclusively on the basis of skeletal patterns, some revealed by good optical microscopes and most now, a fortiori, by sophisticated high resolution electron microscope. Traditionally, the first thing a diatom taxonomist does when he wants to identify a specimen is to “clean” it by burning it away or otherwise destroying all of its organic matter, leaving only its skeletal remains for critical microscopic examination. Most diatoms are too small to see and count with the naked eye; many are mobile and their positions can change constantly. They have short lives, ranging from a few hours to several days. Overall dimensions of diatom shells vary from 0.002 to 2 millimeters.

Diatoms are classified into two major categories, primarily on the basis of shape and symmetry that can be readily observed in living cells and fossils; 1) the centric diatoms typically have discoid or cylindrical cells having radial symmetry in face or “valve” view. A valve is the top or the bottom of the silica frustule. 2) In contrast, valves of pennate (referring to “feathery” patterns of ornamentation on the frustules) diatoms have elongated cells having more or less bilateral symmetry.

Microscopic naturalists were fascinated by these miniature opal structures and by the variety of their shapes and symmetries. Like stamp collectors, the rich diatom collectors organized and funded expeditions into far and remote areas and an active exchange market flourished in Nineteenth and twentieth centuries. The diatom collectors challenged a few individuals who did the sampling and slide preparation to also produce slides with hand picked and hand oriented diatoms. Thum, Müller, Elger and others pioneered this skill in Germany and traded these valuable slides world-wide. The diatoms mounted on glass slides are stored in International herbaria and museums in Washington D.C., New York, London, Berlin, and Vienna and these are made available for diatom experts. The illustrations presented here are the images of diatoms, mounted on aluminum stubs and coated with gold and palladium, captured, with skillful assistance of K. A. Riddle, on high resolution, high voltage scanning electron microscope (JEOL-840), operating at an accelerating voltage of 20 kV at FSU’s Department of Biological Science. The images were digitized and enhanced by the staff of FSU’s Digital Library and Media Center for the display here.

Acknowledgements