Desmids are attractive microscopic single-celled green algae with a typical symmetrical appearance. The cells are divided into two halves ('semicells') that are mirror images of each other and show a remarkable variation in shape and ornamentation. Because desmids prefer clear and nutrient-poor fresh water, they are gaining increasing attention from ecologists for assessing and monitoring wetland areas.
The objective of this site is to illustrate all of the desmid species in the world. At this moment this collection consists of digital images of desmids from samples collected in Europe, North-America and Africa. Material can be fresh or fixed, but this is not indicated in the text. New taxa are added on an irregular basis and existing images can be changed by better ones. Be aware that the pictures of the desmids and the associated scale bars can have different printer resolutions, so the size of the cells are better measured on the screen.
Identifying desmids is a time-consuming job, because taxonomic literature is hopelessly scattered about and hard to obtain. For that reason most specimens are not identified with the original descriptions, usually published in separate articles, but with the more comprehensive monographs and floras. A summary of these books, besides other information about desmids, can be found at the site of the Dutch Desmid Working Group. In those cases where the larger works did not provide a satisfactory answer, 'loose' publications had to be consulted.
The use of photographic pictures on Internet pages provides an excellent tool for comparing specimens from different parts of the world side by side. Pictures from new parts of the world are easily added, existing pictures replaced by better ones and the sequence in which they are presented is easily changed. With printed matter this is impossible. Internet pages also have the potential to (hyper)link information interactively, which provides fast access to related information. These advantages of the Internet are explored too little by taxonomists.
I hope that this site will provide a tool for researchers of various biological disciplines as a start for identifying these beautiful organisms. In the future I hope to add an interactive key, extend the range of references and link the specimens with information about the sampling sites.
Today, modern molecular analysis stirs up the prevailing views about the taxonomic relationships of desmids. Specimen that differ substantially in appearance can be closely related and specimens that are impossible to separate on their morphological characteristics, but originated from different part of the world, can be related more distantly. Where possible these new insights are included in this site.
Micrasterias doveri var. africana from Uganda (above) and Xanthidium calcarato-aculeatum from Zambia (below).