Diatoms have a peculiar feature which sets them apart from most other organisms in terms of size distributions: the size (especially the length) of successive generations of diatoms in a clone decreases during the vegetative part of the life cycle because new cells form inside the existing ones prior to cell division, and as a result the division products are smaller than the parent cell. Concomitant with the size reduction there is often a drastic change of valve shape.
As part of our research into the development of active shape models (ASM) and active appearance models (AAM) we have compiled a high replication test set of diatoms to explore the distribution of shapes and valve face features in morphospace. For our model we have selected 4 taxa of which we have acquired a large number of digital images. These are available here for viewing, ordered by valve length in descending order.

WARNING: Following these links will load up to 100 small images into the frame which may take some time to load, depending on the speed of your connection! Total file sizes are given in brackets.

• Eunotia tenella (Grunow) Hustedt in Schmidt (77 kb)
• Fragilariforma bicapitata Williams & Round (337 kb)
• Gomphonema augur Ehrenberg (496 kb)
• Stauroneis smithii Grunow (366 kb)