Raphe
Definition
A longitudinal slit or canal in the valve of certain pennate diatoms that allows cytoplasmic streaming and active gliding movement across surfaces. Its presence or absence divides pennate diatoms into raphid and araphid groups.
- Structure
- Longitudinal slit or canal in the diatom valve
- Function
- Enables cytoplasmic streaming and gliding motility
- Classification use
- Divides pennate diatoms into raphid and araphid
- Group affected
- Certain pennate (bilaterally symmetric) diatoms
Common questions
Why does the presence or absence of a raphe matter in forensic diatom analysis?+
It is a primary taxonomic feature used to classify pennate diatoms into raphid and araphid groups. Correctly identifying which diatom species are present in a drowning victim's tissue or in water and sediment samples depends on recognising structures like the raphe.
Does every diatom have a raphe?+
No. Only certain pennate diatoms have a raphe; centric diatoms, which are radially symmetric, lack one entirely, and even within pennate diatoms the araphid group has no raphe.
Related terms
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- Epitheca and Hypotheca
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- Frustule
- The silica cell wall of a diatom, composed of two overlapping valves (epitheca and hypotheca). Frustules are taxonomically distinctive, chemically resistant to...
- Sporopollenin vs Biogenic Silica
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- 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...