Passion for Diatoms (book extract)

 

My passion for microscopic creatures started at an early age looking at pond water under my mother’s microscope. When I started a project studying a eutrophic lake in California I needed to acquire skills with the scanning electron microscope. Upon encountering my first diatom from the lake in SEM and seeing its intricate beauty I was hooked! There were almost 100 species of diatoms in our survey. Several were species new to science. Since then I collect diatoms from all over the world (anywhere I happen to travel).

 

Some of the exciting discoveries made during this journey are from occasional samples with diatoms caught in the process of dividing. Mature frustules consist of two siliceous valves, somewhat like a glass petri dish with cover, and a number of encircling girdle bands. When a diatom divides each daughter cell acquires one of the mother cell’s valves. Then the resulting two cells each must produce a new matching valve. This can occur in as little as 20 minutes. Under the light microscope the early forming valves can be seen as “ghost-like” specimens resembling the structure of mature valves but with less silica. With luck, specimens at varying stages give clues to the sequence that a particular species lays down its silica.

 

While diatom are beautiful under the light microscope and have been admired since Victorian times; they are even more exquisite when seen by the scanning electron microscope. At high magnification the surface of the glass shells can mimic floral designs. Although fascinating to scientists, diatoms are also nature’s art at its best. My experience is that the rarely seen immature valves often have stunning geometric designs. For example, below is an image of Asterolampra marylandica and two close-ups of the surface of its forming valve at different stages.