Valve and Girdle Band
Definition
The valve is the flat face of each frustule half, carrying the species-specific pore patterns used for identification. The girdle band is the connecting band around the circumference that joins the two valves.
- Organism
- Diatoms (Bacillariophyta)
- Structure
- Silica frustule made of two overlapping valves plus girdle bands
- Diagnostic use
- Valve pore pattern (striae) supports species-level identification
- Forensic use
- Diatom recovery from lung, marrow, or organs in drowning investigations
Common questions
Why does the valve rather than the girdle band carry the identifying features?+
The valve face carries the species-specific arrangement of pores, ribs, and striae that taxonomists use for identification under light or electron microscopy. The girdle band is a comparatively featureless connecting strip and offers little diagnostic detail on its own.
Why does the frustule survive processes that destroy other tissue?+
The valve and girdle band are built from silica, which resists the acid digestion used to isolate diatoms from lung or bone marrow tissue in forensic drowning cases. This chemical resistance is what makes diatom recovery possible after decomposition has destroyed soft structures.
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...
- Epitheca and Hypotheca
- The two halves of the frustule. The epitheca (larger) fits over the hypotheca (smaller) like a lid over a box. During cell...
- 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...