The silica skeleton of a diatom cell (called the frustule) consists of an epitheca and an hypotheca.

In order to regain their original size, it is usually assumed diatoms have to reproduce sexually, although this has not yet been observed in A. formosa.

[1] Asterionella formosa is known to be susceptible to the chytrid fungus Zygorhizidium planktonicum.

[2][3] If a chytrid attaches to an Asterionella cell, they can, however, protect others of their kind by committing apoptosis, or cellular suicide, stopping the spread of the parasite.

"Effect of environmental conditions on various enzyme activities and triacylglycerol contents in cultures of the freshwater diatom, Asterionella forrnosa (Bacillariophyceae)".