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.
Lacuna
A lacuna is the space or gap in the apical silica of the partectal ring,
between the apex and the subapical projections on the sides of the ring. It may be pyriform (having the shape of a pear).
In Latin, lacuna means gap. The plural is lacunae. Only the genus Mastogloia has lacunae. Mastogloia calcarea is an example.
Lacunae are visible with SEM but usually not discernable with LM.
Image Credit: Bart Van de Vijver
Image Credit: Bart Van de Vijver
Scanning electron micrograph showing the internal view of a valve of Mastogloia calcarea, with the partectal ring in the foreground. The ring has a lacuna, at the arrow, near the apex.