How a diatom turns dissolved silica into a shell
Seawater contains silicon in a dissolved form called silicic acid. A diatom absorbs it and moves it into a tiny compartment inside the cell, where the silica is concentrated and set into a solid structure. This compartment helps control where the material hardens, so the shell’s pattern is built rather than simply coated onto the cell.
The result is a glasslike form of silica, shaped into two overlapping halves. Scientists call the complete shell a frustule. Its pores and openings let the cell exchange substances with the water while the rigid walls help protect it.
A shell that shapes the next generation
When a diatom divides, each daughter cell inherits one half of the old frustule and makes a new half to fit inside it. Because the new piece fits within the inherited one, repeated divisions can gradually produce smaller cells. In many diatom species, sexual reproduction can restore cell size, restarting that cycle.
The shell is therefore more than a barrier: its construction affects how the cell grows and how its descendants are built. The tiny openings that make exchange possible are part of an architecture assembled from dissolved material, one controlled deposit at a time.
