Raphe

The raphe is a structure that allows diatom cells to move over surfaces.

The raphe system is composed of one or two slits, or fissures, that penetrate the valve of some 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. The term originates from Greek, for "seam".

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.