Wall Morphogenesis in Centric Diatoms

Abstract

Diatoms are enclosed within a rigid cell wall which consists of two thecae overlapping at the girdle like a bipartite box. Cell division occurs by binary fission parallel to the valvar plane. Each daughter cell inherits one half of the mother cell wall; each half in both cells then becomes the epitheca, while each new hypotheca is created within an intracellular membrane bound compartment, the “silica deposition vesicle” (SDV) (Figs. 1,3) (Drum et al. 1964; Reimann 1964). This sequence of events causes a decrease in size during successive divisions which at a certain specific stage is compensated for by sexual reproduction which generates a huge auxospore, within which the initial valves of a new clone are laid down. The initial valves are ± hemispherical; the species specific surface form of the vegetative valves is created with the first division of the initial cell.