Raphe
A slit through the valve face of monoraphid and biraphid diatoms, usually positioned along the apical axis. This is the structure which enables a diatom cell to move over substrates.
Image Credit: Marina Potapova
The diatom, Navicula tripunctata is a biraphid taxon, meaning both valves within a frustule possess a raphe system. Here the two branches of the raphe system on a single valve are shown.
Image Credit: Marina Potapova
Karayevia clevei is a monoraphid taxon, meaning only one valve within a frustule possess a raphe system. Here the two branches of the raphe system on the "raphe valve" are shown.
Image Credit: Marina Potapova
Using an SEM, the internal side of the raphe valve of Karayevia clevei shows that the raphe is open to the interior of the cell.