Epitheca and hypotheca
Definition
The two halves of the frustule. The epitheca (larger) fits over the hypotheca (smaller) like a lid over a box. During cell division each daughter cell retains one half and builds a new opposing half, so average cell size decreases over generations until sexual reproduction resets it.
Related terms
- Assemblage
- The full community of diatom taxa present in a sample. The relative frequencies and absolute counts of species in an assemblage reflect...
- Frustule
- The silica cell wall of a diatom, composed of two overlapping valves (epitheca and hypotheca). Frustules are taxonomically distinctive, chemically resistant to...
- Raphe
- A longitudinal slit or canal in the valve of certain pennate diatoms that allows cytoplasmic streaming and active gliding movement across surfaces....
- Sporopollenin vs. biogenic silica
- Pollen and spore walls are made of sporopollenin (a highly resistant biopolymer). Diatom frustules are made of biogenic opaline silica (SiO2·nH2O), a...
- Valve and girdle band
- The valve is the flat face of each frustule half, carrying the species-specific pore patterns used for identification. The girdle band is...
Explained in
- Diatom Biology and TaxonomyThe two halves of the frustule. The epitheca (larger) fits over the hypotheca (smaller) like a lid over a box. During cell division each daughter cell retains...