Raphe

One or two slits, or fissures, through the valve face of monoraphid and biraphip diatoms. If two slits are present, each is called a branch of the raphe. Branches may be separated by a silica thickening called the central nodule. Raphe position may be (1) axial, along the apical axis; (2) eccentric, along one margin; or (3) circumferential, around the whole margin of the valve. From Greek for seam.

The raphe is the structure that raphid diatom cells use to move over surfaces.

Alternative Terms

raphe system
N Tripunctata Raphe
Image Credit: Marina Potapova
This SEM image shows the two branches of the raphe system on a single valve of Navicula tripunctata. This is a biraphid diatom, meaning both valves of a frustule possess a raphe system.
K Clevei Raphe Lm
Image Credit: Marina Potapova
This light microscope image shows the two branches of the raphe system on the raphe valve of Karayevia clevei. This is a monoraphid diatom, meaning that only one valve of the frustule has a raphe system.
K Clevei Internalraphe
Image Credit: Marina Potapova
This SEM image of the inner side of the raphe valve of Karayevia clevei shows that the raphe is open to the interior of the cell.