Glossary
Like the rest of this website, the glossary is a work in progress. If we’ve missed a term, please contact us to let us know the term and references.
Monoraphid
Diatoms that possess one valve with a raphe (raphe valve) and one valve without a raphe (rapheless valve) are termed monoraphid. Monoraphid diatoms exhibit one type of heterovalvy. Example genera include Cocconeis, Achnanthidium and Eucocconeis.
During the ontogeny of monoraphid diatoms, a raphe forms on each valve. One valve completes its raphe and becomes the raphe valve. The other valve fills its incipient raphe with silica, leaving a thickened axial rib, and becomes the rapheless valve.
The genus Nupela includes some monoraphid species and some biraphid species. In this web flora, Nupela is included in the biraphid group.
Image Credit: Marina Potapova
Image Credit: Marina Potapova
These scanning electron micrographs show the rapheless valve and raphe valve of Psammothidium curtissimum. This heterovalvar species is an example of a monoraphid diatom.